Author Topic: EEVblog #1086 - 5 year Solar Power Payback?  (Read 5694 times)

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Online EEVblog

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EEVblog #1086 - 5 year Solar Power Payback?
« on: May 23, 2018, 10:43:20 am »
Dave looks at the 5 year data on his 3kW home solar power system. What was the payback period? And will adding a Tesla Powerwall 2 lithium ion battery energy storage solution be worthwhile?

 
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Offline Brumby

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #1 on: May 23, 2018, 11:55:39 am »
Interesting results - and, yes, the feed in tariffs around Sydney haven't been particularly attractive.

I have contemplated going down this path, but getting to know what gear is out there with its pros and cons is something that I baulk at.  Knowing what to believe in online reviews is one challenge.

Any recommendations?  (For reliable information sources)
 

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #2 on: May 23, 2018, 12:25:34 pm »
Interesting results - and, yes, the feed in tariffs around Sydney haven't been particularly attractive.
I have contemplated going down this path, but getting to know what gear is out there with its pros and cons is something that I baulk at.  Knowing what to believe in online reviews is one challenge.
Any recommendations?  (For reliable information sources)

In terms of what? brands or panels and inverters? installation companies?
I would stress over either.
 

Online orion242

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #3 on: May 23, 2018, 12:55:39 pm »
I think you also need to look at how many people keep their homes =>10yrs.  If most move under that, there is little sense in installing it.

Have an off the grid out building myself, but doubt the costs will make sense in a decade if ever factoring maintenance.
« Last Edit: May 23, 2018, 01:02:05 pm by orion242 »
 

Offline caswal

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #4 on: May 23, 2018, 12:59:27 pm »
Dave, have you seen the Australian Z-Cell home battery storage: https://www.zcell.com/

Completely different chemistry/design to Li-Ion cells. They have started trails in Aus, maybe see if you can get one to play with?
 
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Offline Brumby

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #5 on: May 23, 2018, 01:27:53 pm »
In terms of what? brands or panels
Yes.

Quote
and inverters?
Yes.

Quote
installation companies?
Yes.

Quote
I would stress over either.
 

Offline aqarwaen

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #6 on: May 24, 2018, 12:36:00 am »
dave why you dont build your own battery,to store  all that electricity generated by solar panels?
you could use old smartphones  batteries sent by your viewers,laptop batteries
or  cheap lithium batteries made in china.

it would be any  intresting video,if you decided to make it your own instead..
 

Offline SeanB

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #7 on: May 24, 2018, 01:42:34 am »
Went to Makro today, and they have done the whole parking lot in solar panels, providing shade and power at the same time. There is a corner with a 11kv transformer and control gear to handle this load, and there is a wall of inverters ( one per parking bay panel set) to do the actual work.  Note how they are keeping the inverters cool, using a pair of massive industrial floor standing fans bolted to the concrete to move air over the inverters.  The day today is quite cool, only 27C ambient as I drove around, so those fans are definitely going to be needed in summer when it goes over 30c and humidity goes to the 100% mark. I think the payback they have is pretty good, seeing as the parking lot is pretty big, and they also have done the roof of the complex in solar panels as well, plus the lighting has been changed to LED throughout the store as well, and they have installed all new energy efficient fridges and freezers as well, grouping them into a single cool zone, and another frozen zone, with insulated doors all round on the customer side display shelves.
 

Offline nixfu

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #8 on: May 24, 2018, 02:12:51 am »
This makes the whole building your own Homebrew PowerWall battery bank using free/recycled 18650's look more and more reasonable. See: Youtuber: HBPowerwall.




ALSO, I would suggest you do an analysis of using a traditional large lead-acid or AGM battery storage system cost and see if that has a better payoff than the fancy new lithium based ones.  I bet that would be a much better way to get payoff of your excess daytime energy production.
 

Offline KrudyZ

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #9 on: May 24, 2018, 02:15:14 am »
I think you also need to look at how many people keep their homes =>10yrs.  If most move under that, there is little sense in installing it.

That logic seems a bit flawed. Presumably, having a lower expected electricity bill would be a value add for the new owner as well, so it should increase the resell value of the home.
 

Online coppice

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #10 on: May 24, 2018, 02:18:31 am »
I think you also need to look at how many people keep their homes =>10yrs.  If most move under that, there is little sense in installing it.

That logic seems a bit flawed. Presumably, having a lower expected electricity bill would be a value add for the new owner as well, so it should increase the resell value of the home.
Property agents say few buyers see value in solar panels, so why would they see value in battery packs?
 

Online orion242

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #11 on: May 24, 2018, 02:23:25 am »
You rarely get the full value out of a home improvement when you sell in my experience.  Put a new roof on my current house.  Is the next buyer going to give me an extra 10K?  Doubtful, they will expect the roof doesn't leak...

Even then, why would I shell out the coin for something that may not break even before I sell from a financial point of view?  Save the earth, solar nerd, good feed in rates, ect sure.  Massive tax credits, maybe.  Till I get to the house I plan on dying in, cannot see shelling out the coin myself unless the payback math is ~5yrs or less.
« Last Edit: May 24, 2018, 03:42:47 am by orion242 »
 

Offline ChunkyPastaSauce

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #12 on: May 24, 2018, 03:36:38 am »
Lot of people are going to have large kwh batteries packs parked in garages or connected lots for large portions of the day.... likely to go a long way if standardized.
 

Offline maelli

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #13 on: May 24, 2018, 04:13:49 am »
4000kwh per year, not bad for a 3.0kW system.
My 8.7kW system will give me (first 12 months are soon over) around 10000kwh per year.


Difference Switzerland to Australia apparently 16%.

I also said no to battery, my reasons are different: in winter we need a lot juice, PV production is low.
In summer the opposite.  summer/winter batteries do not exist.

Did you consider installing an electric (heat pump) water heater?
I have one and have it connected to a relay in the solar inverter. Over 800W PV, then heater starts.
Nice side effect: these things dry the air in the basement.


 

Offline NANDBlog

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #14 on: May 24, 2018, 04:23:27 am »
Interesting results - and, yes, the feed in tariffs around Sydney haven't been particularly attractive.

I have contemplated going down this path, but getting to know what gear is out there with its pros and cons is something that I baulk at.  Knowing what to believe in online reviews is one challenge.

Any recommendations?  (For reliable information sources)
Inverters come with long warranty, which are at least 10 years, so they will pay for themselves by then, or if it breaks, you get it repaired under warranty. If you get an inverter from the big 4 (at least here), SMA, Fronius, ABB or SolarEdge, it is very unlikely to make a bad deal. I've seen statistics for 6000 solar installations (no, not panels, these are separate sites), and very few broken inverter. This is not consumer stuff. Also the same goes for the panels themselves. Even the Chinese ones are OK. It is typically not the panel which goes wrong, it is the frames rusting, leaking, and installers with two left hands. It is really hard, or you need a very bad luck to make a bad deal for solar. Or you need to try your best to  select the worst brands.
Also, just make sure it is not shaded, even partial shading is bad. The guy, who was working next to me was training an AI to find installations with shading from the data. And no micro inverters. They dont make any sense financially, but that is the part that actually going to break. Why? Because to keep them competitive, they need to keep the cost down. It is also installed behind the panel (hot), it has to be waterproof (no ventilation), so it is an OK idea turned bad.
You rarely get the full value out of a home improvement when you sell in my experience.  Put a new roof on my current house.  Is the next buyer going to give me an extra 10K?  Doubtful, they will expect the roof doesn't leak...

Even then, why would I shell out the coin for something that may not break even before I sell from a financial point of view?  Save the earth, solar nerd, good feed in rates, ect sure.  Massive tax credits, maybe.  Till I get to the house I plan on dying in, cannot see shelling out the coin myself unless the payback math is ~5yrs or less.

Yeah, so you should just let your home rot away, because it is temporary anyway. BTW everything in this word is temporary.
 

Online coppice

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #15 on: May 24, 2018, 04:43:37 am »
You rarely get the full value out of a home improvement when you sell in my experience.  Put a new roof on my current house.  Is the next buyer going to give me an extra 10K?  Doubtful, they will expect the roof doesn't leak...

Even then, why would I shell out the coin for something that may not break even before I sell from a financial point of view?  Save the earth, solar nerd, good feed in rates, ect sure.  Massive tax credits, maybe.  Till I get to the house I plan on dying in, cannot see shelling out the coin myself unless the payback math is ~5yrs or less.

Yeah, so you should just let your home rot away, because it is temporary anyway. BTW everything in this word is temporary.
No, you need to keep your home serviceable, both so its pleasant to live in and and so its saleable. However any expenditure beyond that has to be viewed in the light of how long you expect to live in the same home. If you are pretty sure you're going to be there a long time, a lot of expensive features make sense. If you are likely to move in a few years, perhaps you should keep the cash to splash out on a future home that might be more long term.
 

Online thm_w

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #16 on: May 24, 2018, 05:31:20 am »
No, you need to keep your home serviceable, both so its pleasant to live in and and so its saleable. However any expenditure beyond that has to be viewed in the light of how long you expect to live in the same home. If you are pretty sure you're going to be there a long time, a lot of expensive features make sense. If you are likely to move in a few years, perhaps you should keep the cash to splash out on a future home that might be more long term.

Sure but most people aren't expecting to move in a few years, if you were it would make sense to save the money to install solar on your new home. The average time spent per home in Canada is ~15 years.

Our payout is a bit better, 10c/kWh and cost for electricity is 13c/kWh. But payback here is more like 20 years, so its not worth it yet, especially since our energy is clean already.
 

Online coppice

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #17 on: May 24, 2018, 05:39:29 am »
Sure but most people aren't expecting to move in a few years.
I don't know how much this varies with countries, but in the UK the average ownership of a property seems to be only 5 or 6 years. I've always found that figure puzzlingly low, but its what the land registry people say.
 
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Online orion242

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #18 on: May 24, 2018, 06:06:50 am »
Looks like the US most people move 11 times in their life, though its more often when they younger.  Average between is going to be 10yrs or less if that's the case.
 

Offline Rutherfordium

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #19 on: May 24, 2018, 07:33:51 am »
Today on the east coast of Canada CBC radio was having a phone in to ask people whether we should force new homes to come with solar panels (apparently something starting in 2020 in California).  I rolled my eyes, and I hadn't even seen the numbers from this video, from a nearly ideal (at least compared to the precipitous maritimes) location.
 

Offline NiHaoMike

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #20 on: May 24, 2018, 11:53:04 am »
Nissan Leaf battery modules are $200/kWh for a few modules, even less in bulk.
Cryptocurrency has taught me to love math and at the same time be baffled by it.

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Offline IanMacdonald

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #21 on: May 24, 2018, 08:25:24 pm »
This makes the whole building your own Homebrew PowerWall battery bank using free/recycled 18650's look more and more reasonable. See: Youtuber: HBPowerwall.

Glad I don't live next door, or I'd be thinking in terms of one of these..

 

Online EEVblog

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #22 on: May 24, 2018, 10:07:12 pm »
No, you need to keep your home serviceable, both so its pleasant to live in and and so its saleable. However any expenditure beyond that has to be viewed in the light of how long you expect to live in the same home. If you are pretty sure you're going to be there a long time, a lot of expensive features make sense. If you are likely to move in a few years, perhaps you should keep the cash to splash out on a future home that might be more long term.

There is something coming on this front, for people who need a non-permanent power storage solution. I'm hoping to get a prototype unit this year.
I had dinner with the designer last month and a good chat about the patented technical solution they have come up with.
 

Online EEVblog

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #23 on: May 24, 2018, 10:09:50 pm »
ALSO, I would suggest you do an analysis of using a traditional large lead-acid or AGM battery storage system cost and see if that has a better payoff than the fancy new lithium based ones.  I bet that would be a much better way to get payoff of your excess daytime energy production.

They are not designed for deep daily discharge like is needed in my case.
 

Online EEVblog

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #24 on: May 24, 2018, 10:14:44 pm »
dave why you dont build your own battery,to store  all that electricity generated by solar panels?
you could use old smartphones  batteries sent by your viewers,laptop batteries
or  cheap lithium batteries made in china.
it would be any  intresting video,if you decided to make it your own instead..

It would takes many months of almost full time work to design and build such a solution for a video.
The problem with people seeing what others have done in videos and say "why don't you do that", is they don't realise the massive amount of work these people have done behind the scenes in order to do that. HBpowerwall is one such example, he's been working on that system for a couple of years.
 

Online orion242

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #25 on: May 24, 2018, 11:00:24 pm »
They are not designed for deep daily discharge like is needed in my case.

So LiPo would be more cost effective vs an oversized SLA bank that doesn't have to take the last life breath out every day?
 

Offline f4eru

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #26 on: May 25, 2018, 04:56:02 am »
Yes, Lithium is now more cost effective than Pb on the long run. In fact PbGel is the worst cost for daily storage !
A small comparative :
Battery type       Lifetime          Battery energy price     Storage price (only battery cost)

Pb Battery Wet        2000 cycles       0,13€/Wh      0.065€/kWh  <- Monthly Maintenance needed, replacement time is 6 Years assuming 1cycle/day.
Pb Battery Gel         1000 cycles       0,27€/Wh      0.270€/kWh  <- extremely bad storage cost, very frequent replacement !!
Lithium LiFePo4      6000 cycles       0,26€/Wh      0.043€/kWh  <- best storage cost ! 18 Years lifetime.
LiFePo4 high end   8000 cycles       0,39€/Wh      0.048€/kWh  <- OK, especially if you want a longer replacement cycle
« Last Edit: May 25, 2018, 05:30:34 am by f4eru »
 
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Online metrologist

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #27 on: May 25, 2018, 05:54:23 am »
At 8min, if 19.95MWh was produced and 7.238MWh consumed, how is that 24.7% of solar produced was used?
 

Offline f4eru

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #28 on: May 25, 2018, 06:14:35 am »
Quote
At 8min, if 19.95MWh was produced and 7.238MWh consumed, how is that 24.7% of solar produced was used?
Easy.
100% of the power produced was used : 24,7% by Dave, 75,6% by someone else
Dave consumed 4.9 MWh of his own production only. The rest 2.31 MWh was consumed by dave off the grid when he didn't produce (at night)
« Last Edit: May 25, 2018, 06:16:32 am by f4eru »
 

Online nctnico

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #29 on: May 25, 2018, 06:15:22 am »
dave why you dont build your own battery,to store  all that electricity generated by solar panels?
you could use old smartphones  batteries sent by your viewers,laptop batteries
or  cheap lithium batteries made in china.
it would be any  intresting video,if you decided to make it your own instead..
It would takes many months of almost full time work to design and build such a solution for a video.
The problem with people seeing what others have done in videos and say "why don't you do that", is they don't realise the massive amount of work these people have done behind the scenes in order to do that. HBpowerwall is one such example, he's been working on that system for a couple of years.
Besides that using random cells is asking for trouble. The idea of using discarded cells isn't new but it will take carefull matching and measuring of the cells to see from which ones you can built a reliable and (more important) safe battery pack. However I'm quite sure we will see batteries for residential (I'm avoiding the word home here because the batteries could also be located at a nearby sub station) storage of electricity becoming more affordable in the future. If a larger part of the electricity supply is going to depend on wind and solar some kind of storage is a requirement to make it all work.
There are small lies, big lies and then there is what is on the screen of your oscilloscope.
 

Offline rrinker

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #30 on: May 25, 2018, 06:26:14 am »
 Yes, about the LAST thing I'd want in my home is a wall full of potentially dodgy used batteries storing that kind of energy. At least if a commercial system burns your house down you have some recourse. Build it yourself with questionable components and you're completely on your own.
 

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #31 on: May 25, 2018, 09:56:37 am »


It would takes many months of almost full time work to design and build such a solution for a video.
The problem with people seeing what others have done in videos and say "why don't you do that", is they don't realise the massive amount of work these people have done behind the scenes in order to do that. HBpowerwall is one such example, he's been working on that system for a couple of years.


I joined instead of stalking just to say - 'Yes' But it bloody works!
 

Offline Brumby

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #32 on: May 25, 2018, 11:58:56 am »
We have no quarrel with the fact that it works ... just that (as I understand it) Dave isn't really set up to put the time into such a project.
 

Offline hbpowerwall

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #33 on: May 25, 2018, 04:50:41 pm »
Not many do - labor of love for sure
 

Online orion242

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #34 on: May 25, 2018, 10:46:22 pm »
So if a lipo in this use case can get ~5k+ cycles, why the hell does my phone battery become utter crap in 2yrs or less?
 

Offline grythumn

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #35 on: May 25, 2018, 11:59:16 pm »
Different chemistries, different battery management. If you limit depth of discharge and charging voltage, you can significantly increase the number of cycles a cell is good for. If you use the full capacity, they're only good for a few hundred cycles.

https://www.powerstream.com/lithium-ion-charge-voltage.htm

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Online metrologist

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #36 on: May 26, 2018, 12:44:28 am »
Quote
At 8min, if 19.95MWh was produced and 7.238MWh consumed, how is that 24.7% of solar produced was used?
Easy.
100% of the power produced was used : 24,7% by Dave, 75,6% by someone else
Dave consumed 4.9 MWh of his own production only. The rest 2.31 MWh was consumed by dave off the grid when he didn't produce (at night)

But that's not what he said. He consumed 7.238MWh of his own solar production, and he also consumed 22.043MWh from the grid. So he consumed a total of 29.281MWh.

I imagine 100% of his solar production was used, some by Dave and some by the grid. If 19.950MWh was produced and Dave only consumed 7.238MWh, he exported 12.712MWh. 36.3% of solar produced was used [directly by Dave].

I see what he means now.
24.7% of his "total energy use" was directly supplied by solar (7.238/29.281).

 

Offline rrinker

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #37 on: May 26, 2018, 01:33:29 am »
Different chemistries, different battery management. If you limit depth of discharge and charging voltage, you can significantly increase the number of cycles a cell is good for. If you use the full capacity, they're only good for a few hundred cycles.

https://www.powerstream.com/lithium-ion-charge-voltage.htm

-R C

Exactly - mine's going on 5 (maybe 4 /2 - I never buy these things when first released) years old (iPhone 5S) and the battery life has not noticeably diminished - but I never let it discharge to the point of the phone shutting down, and since I use it to play music in my car, it gets plugged in constantly whenever I drive somewhere. No deep cycling = nice long life.

Although a power wall to buffer solar production is almost certainly going to be a deep cycle application. Unless you make it of an impractical size that is say 50% greater than your average overnight consumption.
 

Online orion242

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #38 on: May 26, 2018, 01:52:04 am »
Although a power wall to buffer solar production is almost certainly going to be a deep cycle application.

Dimensions
L x W x D: 44" x 29" x 5.5"

From their own internal images of it, the top 1/3rd seems to be the inverter/cooling/wiring.  So that only leaves the bottom 2/3rds for the battery pack.  So ~29"x29"x5" to pack in 13.5kWh of capacity.  Sure hope $6.6K per unit wouldn't need to be swapped out every couple years.

So some ruff math (flawed as my understanding may be)

29x29x5.5 = 4625.5in^3 or ~2.7ft^3 area for battery

Looking on the internets looks like lipo is ~230wh/l

2.7ft^3 = 76.5L
230wh/l * 76.5L = ~17.6kWh

So to suck out the 13.5kWh you must be drawing ~75% of the total capacity everyday.  That extra 25% capacity and the chemistry gets you to the 5K cycles mark?

« Last Edit: May 26, 2018, 02:27:58 am by orion242 »
 

Offline f4eru

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #39 on: May 26, 2018, 02:57:09 am »
An example of "DOD" graph:

For the phone batteries, the problem comes from bad thermal and charge management. A phone battery runs hot and is often charged to 100%.
For lithium batteries to last, charge them to only 85-90% SOC.
« Last Edit: May 26, 2018, 03:11:56 am by f4eru »
 

Online orion242

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #40 on: May 26, 2018, 03:06:42 am »
Yea that's going to be a massive amount of SLAs to get to 5K cycles.

Flip side, 5K cycles from a PW might be a bit optimistic if its 75% DOD to get the rated capacity.
 

Offline NANDBlog

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #41 on: May 27, 2018, 07:49:07 am »
dave why you dont build your own battery,to store  all that electricity generated by solar panels?
you could use old smartphones  batteries sent by your viewers,laptop batteries
or  cheap lithium batteries made in china.
it would be any  intresting video,if you decided to make it your own instead..
It would takes many months of almost full time work to design and build such a solution for a video.
The problem with people seeing what others have done in videos and say "why don't you do that", is they don't realise the massive amount of work these people have done behind the scenes in order to do that. HBpowerwall is one such example, he's been working on that system for a couple of years.
Besides that using random cells is asking for trouble. The idea of using discarded cells isn't new but it will take carefull matching and measuring of the cells to see from which ones you can built a reliable and (more important) safe battery pack. However I'm quite sure we will see batteries for residential (I'm avoiding the word home here because the batteries could also be located at a nearby sub station) storage of electricity becoming more affordable in the future. If a larger part of the electricity supply is going to depend on wind and solar some kind of storage is a requirement to make it all work.
I really hope not. I'm saying this after working with 50Ah Li-Ion batteries, those things are scary. When they fail, they fail big, with gas coming out of them and with a fire that you cannot put out just like that. Besides, It is the government's job to supply continuous uninterrupted power to the people (and keep a police force and repair the roads), not ours. Storage is not like the generation, it can be much more efficiently done if it is centralized.
 

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #42 on: May 27, 2018, 06:52:19 pm »
> Besides that using random cells is asking for trouble.

Speaking as a DIY powerwaller... I think that mischaracterises what we do.

We gather random cells - and then spend a lot of time weeding out the high ESR and low capacity cells - in an effort to use only "good" cells.

And yes - that does take a lot of time. But it's an enjoyable hobby* that usually ends up producing a useful product.

Fun, satisfying and rewarding. For me part of the satisfaction comes from using something that others have thrown away.

But - if you don't want your home energy project to be a hobby then it's much better to just buy a commercial solution.

Cheers, Paul
*Hobby: an activity done regularly in one's leisure time for pleasure.
 

Offline b_force

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #43 on: May 27, 2018, 11:35:52 pm »
I think you also need to look at how many people keep their homes =>10yrs.  If most move under that, there is little sense in installing it.

That logic seems a bit flawed. Presumably, having a lower expected electricity bill would be a value add for the new owner as well, so it should increase the resell value of the home.
Property agents say few buyers see value in solar panels, so why would they see value in battery packs?
I think that really depends were you live.
Enough places were solar panels are actually a huge plus for the value.

Very interesting video.
Yes, a lot has changed the last 10 years
Even the inverters are not so expensive nowadays.
A battery pack is not really going to be efficient, but I think it will work great in places with a lot of outages.
Just came back from a trip around Spain and some places have an outage almost every other week.
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Offline Nauris

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #44 on: May 28, 2018, 05:24:57 am »
Yea that's going to be a massive amount of SLAs to get to 5K cycles.
There are also more premium lead acid batteries out there. Like Trojan industrial solar line as in the graph below. About 3600 cycles at 50% DoD.
 

Offline NANDBlog

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #45 on: May 28, 2018, 06:03:56 am »
Yea that's going to be a massive amount of SLAs to get to 5K cycles.
There are also more premium lead acid batteries out there. Like Trojan industrial solar line as in the graph below. About 3600 cycles at 50% DoD.
If the feed-in tariff is high, then no battery technology is viable, because it is too expensive. If the feed-in tariff is low, then other technologies would provide much better alternative than batteries. Imagine a mini power to gas plant at the backyard, generating methane from water and CO2 from the air. If you sink a tank in the garden, you have practically unlimited capacity, and you can just offset the lower efficiency with more solar panels.
It is really not rocket science, just some more money should be put into P2G and CHP (combined heat and power). If we would spend 1/10 of the money we spent on nuclear research, it would have been a solved problem. But you know, it cannot be used as a weapon.
 

Offline mortderire

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #46 on: May 28, 2018, 06:40:44 am »
Loved the video - much kudos.

Sobering that if Dave can't make it pay in NSW, Auz with buckets of sunshine and some compensation for exported energy. I have pretty much zero chance here in not so sunny, Northern Europe with zero compensation for exporting energy.

I understand now that the key to the system being economical or not, is reasonable compensation for exporting energy. Adding a storage system is prohibitively expensive - appears to only have the effect of extending the period over which the cost of the system has to be paid down, without any guarantee the system is going to last that long without additional investment.

However some reasonable compensation from the power provider for exporting energy into the grid, means there is no need to invest in an expensive storage system - meaning a return on investment might be achievable for people like Dave, i.e. with buckets of sunshine. This is turns into a pretty simple formula of :-

1. How much does the system cost.
2. How much am I likely to generate.
3. How much will I be paid for what I generate.
versus
4. My overall energy requirements.     


It remains less certain for those of us who don't get guaranteed sunshine.
 

Offline f4eru

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #47 on: May 29, 2018, 05:43:59 pm »
Quote
If the feed-in tariff is high, then no battery technology is viable, because it is too expensive.
I don't think so.

There are two use cases where batteries sometimes make sense :
1) If the price of electricity for the consumer is high, and the feed in tariff is low, and your daily average is quite stable, like Dave's past situation you can consume your production in shift. You approach autarcy then.
2) If the feed in tariff is highly variable, with a "smart" meter, you can shift your feed in to the most interesting time. You help to regulate the grid at that point.

Both could make economic sense, or could be uninteresting, depending on many local factors.
But the cases where it makes economical sense are probably still quite niche today.

But two factors will change that :
- Sinking battery costs : Li. Batteries prices drop 30%/Year
- Scaling up of EVs : the adoption of EVs doubles every year, and those can and will probably be reprogrammed as grid stabilization batteries.

In a few years, batteries will change the landscape of electricity pricing and costs.
« Last Edit: May 29, 2018, 05:48:20 pm by f4eru »
 

Online Fungus

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #48 on: May 29, 2018, 06:31:55 pm »
There are two use cases where batteries sometimes make sense :
1) If the price of electricity for the consumer is high, and the feed in tariff is low, and your daily average is quite stable, like Dave's past situation you can consume your production in shift. You approach autarcy then.
2) If the feed in tariff is highly variable, with a "smart" meter, you can shift your feed in to the most interesting time. You help to regulate the grid at that point.

And maybe (3) If you own an electric car that needs charging at night.
 

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #49 on: May 29, 2018, 09:23:37 pm »
There are two use cases where batteries sometimes make sense :
1) If the price of electricity for the consumer is high, and the feed in tariff is low, and your daily average is quite stable, like Dave's past situation you can consume your production in shift. You approach autarcy then.
2) If the feed in tariff is highly variable, with a "smart" meter, you can shift your feed in to the most interesting time. You help to regulate the grid at that point.

And maybe (3) If you own an electric car that needs charging at night.
And as I mentioned above (4) when you have many outages/unstable electricity network.
Maybe even (5) when you need electricity on a place where there is no standard connection (yet)
The costs of getting grid power can sometimes pretty significant.
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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #50 on: May 29, 2018, 10:31:08 pm »
But the cases where it makes economical sense are probably still quite niche today.

Using the car as a grid stabilization or the leftover/replaced batteries?
 

Offline Red Squirrel

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #51 on: May 30, 2018, 08:12:45 am »
The thing with Lithium ion is that they have to be balance charged and also can't be floated.  It makes the system much more complicated to design as you can't really charge the bank while simultaneously using it, You can, but it's more complex to setup.

With lead acid you have a DC bus that runs at a float charge and put your batteries and loads on it, and call it a day.  Maybe measure mid point voltage to alert for faults, and that's it.

But yeah I imagine over time we will see more charge controllers that can handle lithium ion batteries.  You would get a bunch of leads for each cell bank. 
 

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #52 on: May 30, 2018, 03:39:21 pm »
The thing with Lithium ion is that they have to be balance charged and also can't be floated.  It makes the system much more complicated to design as you can't really charge the bank while simultaneously using it, You can, but it's more complex to setup.

If you're charging Lithium ion without a proper controller chip that does all this then you're probably heading for trouble anyway.
 

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #53 on: May 30, 2018, 11:56:48 pm »
Luckily these controllers and other stuff aren't expensive anymore nowadays.  8)
(it's 2018 people)
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Offline Barny

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #54 on: June 01, 2018, 12:00:05 am »
Why always battery storage?

Wouldn't energy storage in rotating masses or compressed air in combination with comressor & air motor an alternative?
 

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #55 on: June 01, 2018, 12:17:20 am »
Those cycles would seem less efficient - too much energy loss, but I guess you could just add more panels.

How much weight how high would = 10kWh?
 

Offline station240

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #56 on: June 01, 2018, 03:26:35 am »
Why always battery storage?

Wouldn't energy storage in rotating masses or compressed air in combination with comressor & air motor an alternative?

No, as the efficiency of all those is terrible compared to batteries.
Compressed air is 30% efficiency round trip
Flywheel looses a lot of energy if conventional barrings are used.
A flywheel in high vacuum with magnetic bearings is 85% efficiency round trip, but with obvious safety issues using it anywhere bar industrial sites.
Lithium Batteries are 90% efficiency round trip
 

Offline Red Squirrel

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #57 on: June 01, 2018, 03:29:55 am »
Luckily these controllers and other stuff aren't expensive anymore nowadays.  8)
(it's 2018 people)

The issue is availability too, I only found a few sites that sell solar stuff here in Canada but all the controllers I found only do lead acid batteries.  So you'd have to build your own if you went that route.  I've seen a few videos of people who did it.  I guess if you measure the current going into the batteries, and the current going to the loads, you can do subtraction to figure out how much current is strictly going into the batteries.  Since lithium ion works on several stages of current for charging, and not just a float voltage, so it's important to measure this for each cell bank.   A cell bank being a group of 18650's in parallel for example.  You would need about 12 of these for a 48v system and individual charge leads for each one, and then the load leads to the inverter from the first and last cell.

I was looking at controller chips for fun and it seems most of them don't balance charge, so really not sure how that works.   I guess you would have one chip per cell bank?

I guess another option is to have two or more battery banks.  One would be charging while the other is discharging and it would switch back and forth once in a while.    Heck you could probably even have a very powerful charger that only does one cell, and it would just alternate between each cell.  I imagine there's lot of different ways to do it. 

I'm surprised that lead acid batteries arn't cheaper these days though, seems to me it's such an old and refined tech, and very recyclable, that it would be cheaper to produce.

 

Offline SNGLinks

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #58 on: June 01, 2018, 10:39:34 am »
My system was free! A company leases the space above my roof and fitted the solar panels at no cost.

In return they get the feed in tariff but I get the power generated!
 

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #59 on: June 01, 2018, 02:06:06 pm »
I was looking at controller chips for fun and it seems most of them don't balance charge, so really not sure how that works.   I guess you would have one chip per cell bank?
The balancing BMS boards I have used use individual comparators specifically designed for that purpose. When the supply voltage to them goes above their threshold, they switch on a MOSFET to connect a balancing load.
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Offline Poe

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #60 on: June 08, 2018, 11:05:03 pm »
So I think the takeaway is that, financially at least, it's better to put your money in your savings?

A $5k investment will very conservatively earn over $1k in 5 years.  Equivalent to $1k in the bank and a brand new solar installation.  That's pre-taxed money as well.

That untouched ultra low risk $5k investment would have made ~$2.5k by the time the solar installation paid for itself (assuming you get paid $0.15kWh).

Due to compound growth, after twenty years you'll have ~$13k in the bank.  Best case scenario for the solar installation is that it's still working, generating the same output, and the cost of of electricity has massively increased.  In this scenario, you might maybe make the same amount.

I'm in a new home and considering solar, but it still feels like home solar is still a lot like solar roadways.




 

Online metrologist

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #61 on: June 08, 2018, 11:57:33 pm »
Zinger!
 

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #62 on: June 09, 2018, 12:54:09 am »
A $5k investment will very conservatively earn over $1k in 5 years.  Equivalent to $1k in the bank and a brand new solar installation.  That's pre-taxed money as well.

That untouched ultra low risk $5k investment would have made ~$2.5k by the time the solar installation paid for itself (assuming you get paid $0.15kWh).

Due to compound growth, after twenty years you'll have ~$13k in the bank.

Yeah ok, right.  Please tell me where I can find this “ultra low risk” investment that will give me that rate of return. I have a stack of money I’d love to put in such an investment (as would many others worldwide).

Also, one obvious point you’ve missed is that the solar panels and inverter are still quite valuable after 5 years. They could “consevatively” be sold for 50% of their original cost after 5 years.

And BTW, where did this strawman come from that solar installations are simply an investment vehicle and nothing more?
 

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #63 on: June 09, 2018, 01:27:38 am »
And BTW, where did this strawman come from that solar installations are simply an investment vehicle and nothing more?

This!
 

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #64 on: June 09, 2018, 01:34:23 am »
The feeling of being able to stick it to the utilities is quite rewarding. Coincidentally, I opened a Fidelity investment account a little over 6 years ago with $5k (minimum at the time) and it is now worth $6800. I've had it in blue chip tech companies, none of the good ones, mind you. Like Nokia, for example (I was hoping the MS deal would pay out more), and a big part of it just sat in a money market. For someone who knows what they are doing, no contest... My neighbor claims to be clearing $100k annually on his investment accounts. That's all he does in his early retirement.
 

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #65 on: June 09, 2018, 03:18:06 am »
The feeling of being able to stick it to the utilities is quite rewarding. Coincidentally, I opened a Fidelity investment account a little over 6 years ago with $5k (minimum at the time) and it is now worth $6800. I've had it in blue chip tech companies, none of the good ones, mind you. Like Nokia, for example (I was hoping the MS deal would pay out more), and a big part of it just sat in a money market.

A stock market account as an ultra low risk investment! :-DD :-DD :-DD

Quote
For someone who knows what they are doing, no contest... My neighbor claims to be clearing $100k annually on his investment accounts. That's all he does in his early retirement.

Everyone’s an investment genius in a bull market. :palm:

Look, there are professional money managers earning literally millions annually in client fees who would never claim to be able to produce the “ultra low risk”  ROE claimed.  The closest would be US Treasuries which are currently considered the “gold standard” in very low risk investment for that kind of time frame. Currently, a 5 year T-Bill yields about 2.7% pre tax - well below the 3.7% or so claimed by Poe. And not only is that pre-tax, it is not inflation adjusted - real world return will be much less than that.
« Last Edit: June 09, 2018, 03:20:53 am by mtdoc »
 

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #66 on: June 09, 2018, 03:24:32 am »
I didn't claim it to be a low risk investment. I said it was a coincidence - the time frame and return to date. That's all. I do not at all think it is a stretch to suspect properly managed investments will outpace your return on a home solar investment. Anything could happen in either market.
 

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #67 on: June 09, 2018, 03:53:32 am »
I didn't claim it to be a low risk investment. I said it was a coincidence - the time frame and return to date. That's all.

Fair enough - but then it's a coincidence without meaning. One could just as easily mention that they had coincidently won the lottery during that time frame.

Quote
I do not at all think it is a stretch to suspect properly managed investments will outpace your return on a home solar investment. Anything could happen in either market.

Well, I think it is a stretch on a risk adjusted basis - It might or it might not.  In fact at the end of 5 years, a risk based investement could return quite a bit more OR it could result in a loss.  Yes, that is true for "properly managed investments".  I can provide multiple examples if needed.

Solar PV equipment - is NOT a financial investment instrument (despite the fact that there are numerous companies whose entire business model is based on that premise).  Nevertheless, over its lifespan - at current prices for the equipment (which you've locked in once you've purchased it),  it will pay for itself and in most cases return multiples of the initial investment in energy savings.

Depending on the energy market where you live, for a standard grid tie installation, done by a reputable installer at a fair price, it may take 5 years or it could take 10 years to pay off your initial investment.  But after that - for the 25-30 years lifespan of the PV panels and 15-20 year expected lifespan of a quality inverter, you are earning a good return on your original investment.



 

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #68 on: June 09, 2018, 05:18:18 am »
I didn't claim it to be a low risk investment. I said it was a coincidence - the time frame and return to date. That's all.

Fair enough - but then it's a coincidence without meaning. One could just as easily mention that they had coincidently won the lottery during that time frame.


It is just a coincidence in the context of what was said previously, which pretty much mirrored my experience and result to a tee, aside from it not being a "savings" account:

So I think the takeaway is that, financially at least, it's better to put your money in your savings?
A $5k investment will very conservatively earn over $1k in 5 years.  Equivalent to $1k in the bank and a brand new solar installation.  That's pre-taxed money as well.

It's also a coincidence that I am thinking of home solar, and I'm sure that doesn't have any particular 'meaning' either. An average ~5% return is not unlikely and it is nowhere close to the left-field lottery comment.


Quote
I do not at all think it is a stretch to suspect properly managed investments will outpace your return on a home solar investment. Anything could happen in either market.

Quote
Well, I think it is a stretch on a risk adjusted basis - It might or it might not.  In fact at the end of 5 years, a risk based investement could return quite a bit more OR it could result in a loss.  Yes, that is true for "properly managed investments".  I can provide multiple examples if needed.

Solar PV equipment - is NOT a financial investment instrument (despite the fact that there are numerous companies whose entire business model is based on that premise).  Nevertheless, over its lifespan - at current prices for the equipment (which you've locked in once you've purchased it),  it will pay for itself and in most cases return multiples of the initial investment in energy savings.

Depending on the energy market where you live, for a standard grid tie installation, done by a reputable installer at a fair price, it may take 5 years or it could take 10 years to pay off your initial investment.  But after that - for the 25-30 years lifespan of the PV panels and 15-20 year expected lifespan of a quality inverter, you are earning a good return on your original investment.

It could, it could not...a whatif scenario? Jeebus man, what is the overall average return on the type of investments we are discussing? There are losers and winner of course. I would look at index funds and etc., do you have any dataset to argue with? There is generally a predicable  average rate of return, you diversify, and you understand I'm sure... Yeah, rocks could fall from the sky and break your panel - but that never happens, huh? It would be a silly argument against solar - just as silly as the whatif. I'm disappoint!

I think it's down to egos, if one were to really look at the numbers.

Solar PV equipment - is NOT a financial investment instrument...
...for the 25-30 years lifespan of the PV panels and 15-20 year expected lifespan of a quality inverter, you are earning a good return on your original investment.

I never said PV is a financial investment vehicle and argued against that philosophy with you know who, but the original point was made and I appreciate and understand the validity of it. I think people usually install home solar to result in a financial positive, if it is not for technical or political reasons, so it would be foolish not to consider alternate ways of achieving the ultimate goal.

For example, my mum wants to install a small solar system to power an electric fence that presents technical challenges to tie to the grid, and also the city does not allow residential electric fences tied to the grid. No financial incentive at all - it will be a grossly predictable money looser, down to the exact dime.

« Last Edit: June 09, 2018, 05:26:29 am by metrologist »
 
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Online mtdoc

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #69 on: June 09, 2018, 06:30:30 am »

It could, it could not...a whatif scenario? Jeebus man, what is the overall average return on the type of investments we are discussing? There are losers and winner of course. I would look at index funds and etc., do you have any dataset to argue with? There is generally a predicable  average rate of return, you diversify, and you understand I'm sure... Yeah, rocks could fall from the sky and break your panel - but that never happens, huh? It would be a silly argument against solar - just as silly as the whatif. I'm disappoint!

The issue is that Poe stated that there is an "ultra low risk investment" that will magically turn $5000 into $6000 in 5 years.  The reality is that such an investment does not exist. Your coincidental anectdote of your stock market account is completely irrelevant.

Sorry, but if you think index funds are a low risk investment or that looking at average rate of returns (over which timeframe?) or diversification, etc is some magical way to guarantee a low risk ROE then you are demonstrating a level of financial naivety that would be difficult to fully demonstrate without getting way off topic here (learn about VaR as a start).   

If you want datasets, look at any of the major US or world stock market indexes and you will find multiple incidences where a 5 year horizon yielded a very low or negative return.  If you're talking longer time frames just look at the return of the Nikkei 225 (the Japanese market index) since 1990 (28 years!).


BTW - the extremely rare event "rocks falling from sky damaging solar panels" would be covered by most homeowners insurance.  There is no equivalent insurance for the very ordinary and common event of a stock market correction or bear market.

« Last Edit: June 09, 2018, 06:34:20 am by mtdoc »
 

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #70 on: June 09, 2018, 07:54:03 am »
Are you arguing that an average 5% return in these kinds of investments is a rarity, or even unlikely?

Poe's example turns $5k into $6k in 5 years. I am looking at a 5yr, 3.2% rate CD. You compound that over the term and tell me again what you think about how non-existent an ultra-low-risk investment like this really is. I don't get it :-//

Note this is from a credit union with qualifiers.
 

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #71 on: June 09, 2018, 08:21:51 am »
mtdic - I prefaced my comment by limiting the takeaway to the financial aspects.  I'm unaware of any other sensible reasons for an install, but would love to hear them.

So I think the takeaway is that, financially at least, it's better to put your money in your savings?
...

NOTE: The following is regarding the FINANCIAL implications alone..

Data for both investments are well documented.
http://lmgtfy.com/?q=average+401k+return

Inflation-adjusted returns on solar investments are similar to Dave's while the average 401K return is >5%. 

Would love to see the rational and data that discredits this... because, as I mentioned before, I'm considering installing solar panels.  The tax payers aren't going to fund the credits forever.

To judge risk, I looked at typical 'low-risk' Vanguard index performances minus fees for various start/end dates and charted the % of return vs frequency.  Even through the 2004 to 2012 years, the result was basically a bell curve with the most likely outcome being an inflation adjusted compound return of 6%. 

I did something similar with solar installations.  Unfortunately, even when I look at the least risky solar investments (most expensive installations), they still are outperformed by even the higher risk lower average return investments.

I then realized the exact numbers don't matter after twenty years because this is apples and oranges.  One investment is a linear growth while the other is exponential.  Would you rather your $5k earn $600 every year or a compound 5% interest?  Even if it occasionally drops to 1% the latter will always exceed the former. 

Just my thoughts.  Would love to discuss it with someone that hasn't drank the kool-aid and can show me where my logic fails.
 

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #72 on: June 09, 2018, 08:54:47 am »
Solar PV equipment - is NOT a financial investment instrument (despite the fact that there are numerous companies whose entire business model is based on that premise).  Nevertheless, over its lifespan - at current prices for the equipment (which you've locked in once you've purchased it),  it will pay for itself and in most cases return multiples of the initial investment in energy savings.

Depending on the energy market where you live, for a standard grid tie installation, done by a reputable installer at a fair price, it may take 5 years or it could take 10 years to pay off your initial investment.  But after that - for the 25-30 years lifespan of the PV panels and 15-20 year expected lifespan of a quality inverter, you are earning a good return on your original investment.

I live in Sunny Tucson, Arizona, and we put solar panels on the roof last August. We expect that the payback period will be 5 years, and you're indeed correct, the panel "lifetime" is 25 years, and by that they mean they're still producing 90% of power when new. To me, that means in 25 years they're still working like a champ.

And yes, the expectation is that utility power costs will only increase; how much depends entirely on how much the regulatory commission will allow them to charge. The proposal for my power system showed payback time with assumptions that the utility price will increase 5% per year, 0% per year and -5% per year (this last one is a pipe dream). But I just checked my bills from the last couple of years. The bill separates out generation charges and transmission charges (under the assumption that somehow you could sign up for an alternative generation provider). The increase in generation costs from July 2016 to July 2017 was about 2.17%. The increase in transmission cost for the same time period was 17.6%! And the kicker is that the transmission cost is much larger than the generation cost. The July 2017 bill was $60 for generation and $144 for transmission. So I think that my payback will actually be three years, assuming similar yearly increases in transmission costs.

To address the point made earlier about "if you sell the house in say three years, will you recoup the cost of panel installation?" I spoke to a friend who is a real estate agent and she was like "HELL YEAH." She was clear: if it's a purchased system it's definitely a positive; buyers do want solar power here, and a $15,000 premium over the house next door is in the noise, especially if there is any kind of bidding war where the next bid is $20,000 more. However, if it's a leased system, that's a turn-off, because nobody is quite sure how the leases transfer. (I asked my next-door neighbor, who has a leased system, how that would be handled, and he admitted he did not know.)

One more thing. The installed cost of the system on my roof was $18,700 and we got $6,500 back in federal and state tax credits, so total cost to me was ~$12,000. But this is for a 60-year-old house that had the system retrofitted. For new construction, the cost would be less, as the wiring and the labor are integrated into the home's electrical design and construction. And for new construction that costs $250,000 (high for here), adding $10,000 price is in the noise, really. When I read that California was requiring solar panel installation on all new construction starting in 2020, I thought that was a no-brainer. When houses cost $500k and up, solar power cost is irrelevant. (People pay more for their kitchens.)
 

Online mtdoc

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #73 on: June 09, 2018, 10:09:11 am »
Are you arguing that an average 5% return in these kinds of investments is a rarity, or even unlikely?

Again, you are demonstrating a lack of understanding of the concept of investment risk. If $5000 invested in the stock market returns 5% or more  over 5 years 50% of the time, 0-5% 40% of the time and < 0% 10 % of the time, then no it’s not a rarity. But that is very, very different than  Poe’s claim of an “ultra low risk” investment yielding 3.7%.

Risk adjusted return is a real thing in the investment world.

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I am looking at a 5yr, 3.2% rate CD.
Show me. What currency? What is the inflation rate in the country?  Not in an insured US bank.  Real returns require that is taken into account. I can probably earn >20% on  a CD on a country whose currency/inflation rate means real returns are likely to be less tha 2%.
 

Online metrologist

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #74 on: June 09, 2018, 11:51:03 am »
Are you arguing that an average 5% return in these kinds of investments is a rarity, or even unlikely?

Again, you are demonstrating a lack of understanding of the concept of investment risk. If $5000 invested in the stock market returns 5% or more  over 5 years 50% of the time, 0-5% 40% of the time and < 0% 10 % of the time, then no it’s not a rarity. But that is very, very different than  Poe’s claim of an “ultra low risk” investment yielding 3.7%.

Risk adjusted return is a real thing in the investment world.

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I am looking at a 5yr, 3.2% rate CD.
Show me. What currency? What is the inflation rate in the country?  Not in an insured US bank.  Real returns require that is taken into account. I can probably earn >20% on  a CD on a country whose currency/inflation rate means real returns are likely to be less tha 2%.

I'm not going read your trivial wiki references. They do not at all indicate financial performance, so they are irrelevant. You obviously have some ulterior objective or are talking about something else.

The point is already made in actual performance figures.

I'm referencing a NCUA backed US federal credit union. Qualifying balances are $500k to earn some of the offers I see, so you will not likely see them.

I am not talking about risk assessment anyway. I'm talking about standard returns on the typical kinds of investments being discussed. YOU can even google this yourself. What is wrong with you?

I am reminded of what this forum is about and will go back to it. Hopefully, you will glance at the attached and have a nice day.



 

Online mtdoc

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #75 on: June 09, 2018, 02:40:12 pm »
I'm not going read your trivial wiki references.
Well, you've demonstrated you have no understanding of or interest in learning basic investment concepts so I'm not surprised.

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The point is already made in actual performance figures.
  Yes - as I stated, look at any major financial indices and you will see that there are many 5 year  periods where diversified stock returns are negative.  That is the point that you seem unwilling or incapable of conceding after claiming earlier that a diversified or "properly managed" stock portfolio would provide the "ultra low risk" investment that Poe claimed existed.  Now you've switched to CD claims.

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I'm referencing a NCUA backed US federal credit union. Qualifying balances are $500k to earn some of the offers I see, so you will not likely see them.

I looked into the one 3.2% 5 yr CD listed on the screenshot you provided. It is a 3 week old quote (rates have since fallen),  from a very sketchy credit union, with very poor ratings, not FDIC insured and is only available by paying to be a member which is available to only a very limited group of people.  Even if it was available, it does not qualify as "ultra low risk"

BTW This not an academic exercise for me. I have a very large amount of money sitting in short term T-Bills and I would love to find a "ultra low risk" place where I can earn 3.7% over 5 years. I will contact them and investigate. And, if I find it I could likely make a nice commission getting many other's to put there money there as well.

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I am not talking about risk assessment anyway.
  Clearly, since you don't seem to understand what it means.  But that is the whole point underlying the  claim that there exists the "ultra low risk" investment yielding 3.7% that Poe claimed and you supported.

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I'm talking about standard returns on the typical kinds of investments being discussed.
What "typical kinds of investments?"  Index funds? CDs?  You've failed to provide any concrete evidence that there is a currently available "Ultra low risk" investment that yields what Poe says.

The truth is it doesn't exist.  Hint: 5 year treasuries are currently yielding less than 2.8% and the best you will find in a CD from a reputable FDIC insured bank is 2.85% or so.  That is how it must be - if the spread between treasuries and CDs was greater than it would represent an arbitrage opportunity that other banks would take advantage of and the spread would narrow again.

The "ultra low risk" investment with a ROE well above T Bills that you are claiming to exist is the financial equivalent of a "Free Energy Device" and to anyone who understands the underlying investment and risk principles, you appear like the typical physics naive and gullible free energy groupie.
« Last Edit: June 09, 2018, 03:02:52 pm by mtdoc »
 

Offline Poe

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #76 on: June 09, 2018, 03:18:19 pm »
These are the types of comments I was worried about.

Anecdotal evidence isn't helpful because it's one questionable data point.  Here's mine.. I haven't touched my 401k other than to put money in and it's 20 year RRR is 6.97%.  Completely ignored through the worst market in history.
https://www.investopedia.com/terms/r/realrateofreturn.asp

Here's real unbiased data on what electricity historically costs in the USA.  They have lots and lots of data.  Even Arizona.
https://www.eia.gov/totalenergy/data/annual/showtext.php?t=ptb0810
On aggregate, it's increasing with inflation.  Arizona's transportation rates are increasing due to a massive surge of Californian's moving there BTW. 

metrologist - I don't think the CD is really evidence of a 'good' investment because it's zero risk.  Return and risk are two sides of the same beast so this zero risk investment has a real rate of return of only -1.77% (negative).  So you're guaranteed to lose ~9% of your CD investment's worth due to inflation.  After 5 years your initial $5k will only be able to buy what $4500 can buy today. 
http://www.investinganswers.com/financial-dictionary/ratio-analysis/compound-annual-growth-rate-cagr-1096

Inflation is ignored with most solar payback calculations as well though.  The longer their calculated ROI, the longer the real ROI actually is.  If they calculate 5 years, it's actually 6.5.  If 10, it's 15.  And that's just to break even and replace the system.

mtduc - I'm having a hard time understanding what you're saying.  Are you saying that it's more likely for a solar installation's inflation-adjusted return to exceed a typical a 401k investment's real rate of return for any given time period?    Or are you saying that only a zero risk investment is worth comparing to a solar installation?

You're not commenting on the point I made that one is linear growth and the other is exponential.
http://smallbusiness.chron.com/difference-between-compound-growth-exponential-growth-simple-growth-61107.html

Do you feel the average savings investment is extremely risky or yields less than a 5% RRR?

Less insults and attitude, more data and rationale please.

I would love to discuss things like how 401Ks are pretax/tax-deferred money so an actual larger investment, possible employer matching increasing it further, and how without tax payers subsidizing solar installations to the tune or 30%.. all ROI calculations will more than double.

Cool stuff to think about.
 

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #77 on: June 09, 2018, 03:51:48 pm »
Inflation is ignored with most solar payback calculations as well though. 
True. But in the case of solar PV equipment (a “hard asset”) and energy, inflation is likely to help you. Solar PV panel prices have bottomed and they are now a commodity product susceptible to inflation effects on raw materials. Same for inverters and especially the copper in the BOM of a solar installation. And utility provided electricity rates are likely only headed one way.

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mtduc - I'm having a hard time understanding what you're saying.  Are you saying that it's more likely for a solar installation's inflation-adjusted return to exceed a typical a 401k investment's real rate of return for any given time period?    Or are you saying that only a zero risk investment is worth comparing to a solar installation?
I’m saying that it’s a strawman argument to try and make a direct comparison between a solar PV installation and a financial investment instrument, BUT if you are going to go that route then yes, the only fair comparison is to one with similar risk profile such a US treasuries. It is also only fair to compare over the working life of the solar PV equipment- not stop at 5 years or whatever the point is that the equipment has paid for itself.

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Do you feel the average savings investment is extremely risky or yields less than a 5% RRR.

It is an undisputable fact that  currently there is no safe savings investment available that yields anywhere close to 5% in real terms. Even 30 year Treasuries are almost 200 basis points away from that even without taking inflation into account (and yield may even approach zero if you do!). Thats just the reality of the current low interest rate world we live in. (It is by design of the central banks BTW, who have been desperate to discourage savings and encourage speculation in high risk financial instruments - hence the current bubble 3.0)
« Last Edit: June 09, 2018, 04:01:05 pm by mtdoc »
 

Offline GeorgeOfTheJungle

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #78 on: June 09, 2018, 06:31:01 pm »
At first sight it seems to me it would be fair, perhaps, to get back for free as many kWh as you've put into the grid.

What's not right, as it happens in Spain, is when the rest of the spaniards have to pay you up to 4x as much. Why? Fuck you I say. I don't want to have to pay more because you've put PVs on your roof!

Some years we're paying more than 8 billion euros more, out of our pockets via the electricity bills, for this reason: the "primas a las renovables". And these 8 billions are not even VAT free, so add another 21% on top of that, just because yes.

« Last Edit: June 11, 2018, 10:29:54 pm by GeorgeOfTheJungle »
 

Offline Poe

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #79 on: June 11, 2018, 07:41:30 am »
I understand how higher electricity costs would help the solar investment, but inflation only affects price, it's independent of relative cost.  So while the price of electricity will surely rise due to inflation, the relative cost might remain the same or even decrease.  e.g. If your hourly wage can buy 100kWh today, the same might be true in ten years as both increase similarly.  Historically (reference the past links) the cost hasn't changed much so there's no data supporting the idea it will MASSIVELY increase enough to matter.

Now the other part I really don't understand.  How would inflation effects help when buying a PV installation today or its return ten years from now?  All components have been susceptible to inflation effects.  If the cost to replace your PV installation has doubled in price after 20 years due to inflation, how does that help?

Obviously the two investments can/have/will be compared.  I can't strawman your argument if I don't understand what it even is.  I think this is what you're saying:

Any investment with an equivalent 'risk' to that of a solar installation will have a worse financial return.

Is that accurate?  If not, tell me why.  If yes, we can discuss 'risk'. 

I think it's unrealistic to limit the investment comparison to insured savings, pretending a PV installation is as 'safe' as a bond.  FDIC deposits and government backed bonds are not an investment: https://www.sec.gov/rss/ask_investor_ed/saveinvest.htm
Insured savings like these serve a different purpose than actual investments and will always lose value because they're a main factor in what determines inflation itself.

Please look into linear vs exponential growth.  I think this is the biggest reason why solar doesn't make sense as a financial investment. 


I was going to invest in solar to diversify, thinking of it as somewhere between cash and something with a decent rate of return.  Unfortunately even with ideal circumstances, the relative risk increases and real return rate decreases with time.  So it only makes sense if I was going to continuously increase my PV size.  I think this is the SolarCity business model.

GeorgeOfTheJungle - It's similar in the USA, except instead of making the wealth redistribution based on energy production, it's based on the installation cost.  30% of qualifying PV installations are paid for by people who can't afford their own PV installation, through higher electricity prices.




 
« Last Edit: June 11, 2018, 07:44:02 am by Poe »
 

Online mtdoc

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #80 on: June 11, 2018, 01:20:33 pm »
I understand how higher electricity costs would help the solar investment, but inflation only affects price, it's independent of relative cost.
Now the other part I really don't understand.  How would inflation effects help when buying a PV installation today or its return ten years from now? 

Inflation is a monetary phenomenon.  It is the erosion of purchasing power. It negatively impacts monetary assets only. In an inflationary environment, the cost of hard assets (eg. Solar PV equipment, Copper wire, etc) increases, so in monetary terms, the earlier you buy them the better.

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  I can't strawman your argument if I don't understand what it even is
Your strawman comparison occured before I posted in this thread.

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Any investment with an equivalent 'risk' to that of a solar installation will have a worse financial return.

Is that accurate?  If not, tell me why. 
  No, solar installations are not financial instruments, arguing as if they are is the strawman you created with your initial post.

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I think it's unrealistic to limit the investment comparison to insured savings, pretending a PV installation is as 'safe' as a bond.
In the context of the strawman your post created, it is the only accurate comparison.  The fact is, a solar PV installation, covered by homeowners insurance is as safe, or safer than a bond.

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FDIC deposits and government backed bonds are not an investment

Your arguing semantics, but nevertheless, it's is a distinction without meaning.  The reality is that an individual with available capital, has to choose what they will do with their money.  Invest it in their home (eg a solar installation)?, invest it in other hard assets?, invest it in stocks?, a business venture?, bonds? or put it in a savings account or CD. In the financial management world, US T-bills are considered the safest (for now) and most liquid place to earn a return on one's excess capital. Until the new central bank made low interest world (post Greenspan era), T-bills were often a place to get a very good risk adjusted return your investment. Anyone who bought 30 year treasuries yielding 14% in the yearly 1980s can attest to that.

And when considering what to do with excess capital, everywhere and always there is a direct relationship between return and risk - that is the "Ohm's law" of financial management:



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Please look into linear vs exponential growth.

Really? 7th grade math on this forum.   :palm:
« Last Edit: June 11, 2018, 01:54:45 pm by mtdoc »
 

Offline GeorgeOfTheJungle

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #81 on: June 11, 2018, 11:25:46 pm »
GeorgeOfTheJungle - It's similar in the USA, except instead of making the wealth redistribution based on energy production, it's based on the installation cost.  30% of qualifying PV installations are paid for by people who can't afford their own PV installation, through higher electricity prices.

And that's not fair because in that bussiness model I'm forced to buy your product even if I don't want to, that's the mafia way of doing bussiness, and it's backed by the state. Thumbs down.
 

Offline Poe

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #82 on: June 12, 2018, 04:59:03 am »
Mtdic - I'm truly trying to understand your argument, but you just appear defensive.   :(

You haven't explained how inflation helps such an investment.  You defined inflation, so I thought you understood what it means, but you also said that inflated prices somehow improve the solar investment that was already made.  Please explain.  Maybe respond to my previous example or data? 

You called any unfavorable comparisons with traditional investments a strawman argument because, according to you, solar isn't an investment.  This I really don't understand because it fits the definition (https://en.wikipedia.org/wiki/Investment).  Even if a different word is used, you appear to understand that people will consider buying solar for a return and will compare it to other financial investments.  I'm one of those people and I'm asking specifically: Which do you think makes the most financial sense and why.  It's clear you would answer solar, but please help me and others by explaining your decision.

It would be understandable if you said that any form of risk is too risky for your personal situation.  Unfortunately, your comments have only implied that sentiment, so I can't be certain.  You appear to be avoiding the risk discussion altogether and acting as if all investments are like repeatedly "letting it ride" at the craps table.  Like one day it will all just disappear instead of risk just affecting the degree of rate swings.  Basically, I'd like to know if we just disagree on the 'risk' part.

My comment about growth was not meant to be insulting.  I just got the feeling that you didn't understand this concept because you wanted comparisons to extend beyond 5 years.  Seemingly oblivious to the fact that this is exponentially worse.  As the period increases, the compound-growth curve (green) will exponentially exceed the linear-growth line (red).  Dave's ROI is ~10years (with typical 15cents kWh and inflation factored in) this is roughly where the red and green lines intersect as well.  So we could do comparisons at 25 years if you'd like, but it might not have the outcome you were hoping for.


edit - Just in case it wasn't clear... the solar investment installation is the red line with a fixed dollar return each year and the green line is the compound growth investment.

« Last Edit: June 12, 2018, 05:04:00 am by Poe »
 

Online metrologist

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #83 on: June 12, 2018, 07:25:36 am »
metrologist - I don't think the CD is really evidence of a 'good' investment because it's zero risk.  Return and risk are two sides of the same beast so this zero risk investment has a real rate of return of only -1.77% (negative).  So you're guaranteed to lose ~9% of your CD investment's worth due to inflation.  After 5 years your initial $5k will only be able to buy what $4500 can buy today. 
http://www.investinganswers.com/financial-dictionary/ratio-analysis/compound-annual-growth-rate-cagr-1096

Inflation is ignored with most solar payback calculations as well though.

The challenge was not to identify a 'good' investment, nor to meet any other qualifying semantics. It was simply to identify a 'low-risk' investment that would turn $5k into $6k over a 5 year period (or basically match Dave's results). A federally insured NCUA share account at 3.25%, amortized quarterly, comes awful close.

I'm not sure how much Dave's hardware has depreciated in value over that time, and I also wonder if homeowners insurance would really cover a damaged panel, given typical deductibles. Maybe, and then maybe the premium is higher to cover the system, or will be after a claim. IIRC, the MFG replaced Dave's panel, but I'm sure that is not their policy and Dave enjoyed the benefit of his position (it would have been mutual).

Since I know my rates are going to go up quite a bit due to new time of use pricing (13C 10 years ago, ~22C now, expected 45C peak next year), Solar probably has a lot more potential for me, assuming I can convince my neighborhood to cut down some heritage trees. The barrier to entry here is not merely a small financial membership fee. Also, to get a system like Dave's here is going to cost a heck of a lot more than $5k, and there is going to be installation and etc.

I appreciate your contribution to the discussion and will happily check back later to peruse the developments.
 

Online mtdoc

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #84 on: June 12, 2018, 09:10:34 am »
You haven't explained how inflation helps such an investment.  You defined inflation, so I thought you understood what it means, but you also said that inflated prices somehow improve the solar investment that was already made.  Please explain.

I explained very clearly. I’m not sure why you are unable to comprehend why inflation favors holding hard assets and disfavors holding monetary assets. It’s a pretty basic concept. Lots available online and in finance textbooks if you need more information.

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You called any unfavorable comparisons with traditional investments a strawman argument because, according to you, solar isn't an investment.
No that’s NOT what I said. I said a PV installation is not a financilal instrument. It is an investment in the same way a new roof or better insulation or windows might be an investment.

Again, these are pretty basic concepts. I think maybe you are just being provocative. If not, I’m sorry - perhaps do some reading on line or take a course at a local college.

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It would be understandable if you said that any form of risk is too risky for your personal situation.  Unfortunately, your comments have only implied that sentiment, so I can't be certain. 

Um, I’m not sure where you got that. For many years, I been actively involved in the financial markets, in everything from actively trading option and futures contracts on the long and short side (high risk) to directly buying US Treasuries (low risk) to everything in between. My current focus is on acquiring some income property (single and multifamily rentals) -though that market has gotten toppy as well. This requires capital held in a low risk, liquid financial instrument so it’s ready to deploy when a bargain comes along or when the markets correct.  However, I do still currently hold and actively trade some high risk financial instruments.

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You appear to be avoiding the risk discussion altogether
Well, since I was the one who introduced the idea of investment risk into this discussion, have mentioned it in every one of my posts here and suggested that RaR and VaR are important concepts for anyone who wishes to better understand the role of risk in comparing investment returns, it’s pretty bizarre that you woud say that.

Are you trolling? If not and you just have reading comprehension difficulties, my apologies. Either way, I don’t think we’re getting anywhere.  Good luck in you financial pursuits.
« Last Edit: June 12, 2018, 09:22:16 am by mtdoc »
 

Online Bassman59

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #85 on: June 13, 2018, 02:25:25 am »
I said a PV installation is not a financilal instrument. It is an investment in the same way a new roof or better insulation or windows might be an investment.

This is the whole of the argument.

A reasonable homeowner makes "investments" in the property to improve quality of life. Better windows make HVAC more efficient, which in turn makes the house more comfortable. A roof that doesn't leak is a good thing. Some people like to have a swimming pool in the back yard, and installing one costs as much, if not more, than rooftop solar.

(I see a lot of people making home improvements only because they want to sell the property. I don't understand that -- why not do the improvements when you move in, so you can enjoy them?)

Rooftop solar means that I'm doing my little part to reduce dependency on fossil fuels. Am I a hypocrite because I drive a gasoline-powered car? Perhaps, although I do ride my bike to work as often as possible.
 

Offline Poe

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #86 on: June 14, 2018, 12:17:57 am »
Hard assets only benefit from inflation by value though.  So you'd have to sell them to benefit in any way, right?  But if they depreciate more than inflation, like new cars and solar installations, you'd lose money by selling them.  So it's best not to sell them, right?  In which case inflation had no effect?  ...or is selling them after 5 years for half of what it cost you part of your strategy?

Not trying to be provocative or troll, just feel like I'm playing word game or red herring whack-a-mole.  No, solar isn't a financial instrument, but why does that preclude the comparison?  They're both investments, regardless of what you want to call them.  One has a linear return and possibly lower risk.  One has an exponential return and possibly higher risk.... depending on what you're comparing since there's actually a large gradient of risk/return options for the latter.  People have limited wealth so they decide between financial choices by making a comparison.

I could understand if your 50+ years old and lowered your retirement portfolio risk to insured 'savings', which lags inflation.  Solar might be a good idea for this life situation.  Although, if you're younger and already depending on some form of retirement planning to beat inflation by an amount which would exceed the solar return, why not put the money in there instead since you're already taking that risk?  Especially if, like many people, you're not already maxing out what your employer matches or would not max out in order to pay for the solar.

If anyone knows of good unbiased data that attempts to objectively weight these options, please post it.

The following is typical of what I find.. conservatively plan on 5% real rate of return (from passively managed 401k plans) and >10 year ROI solar installations.
http://www.interest.com/401k/news/kind-return-expect-401k-plans/
https://www.solarpowerauthority.com/how-much-does-it-cost-to-install-solar-on-an-average-us-house/
https://www.investopedia.com/ask/answers/041015/what-rate-return-should-i-expect-my-401k.asp
https://www.nrel.gov/news/press/2017/nrel-report-utility-scale-solar-pv-system-cost-fell-last-year.html

« Last Edit: June 14, 2018, 11:17:38 am by Poe »
 

Offline Poe

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #87 on: June 16, 2018, 01:19:32 am »
My solar neighbors had some input relating to the solar risk.

Their export rate decreased and a few 'supplier transportation taxes' were added at the start of this year.    Effectively they're making 50% less on exported electricity.  It wasn't something they had planned on.

One paid for the install out of pocket and didn't export much due to a smaller install, so no worries.  Another has a Tesla leased install (Telsa estimated an ROI at 7.5years) with double the capacity his family needs, so he got hit harder. 

That Tesla lease is odd in that his payback depends on how much money he generates.  So based on the first year's production, his ROI was going to be ~ ten years (not 7.5).  After these price changes though, it's now closer to 16.  It might be further out since he's still using Tesla's $kWh model where they assume the price of electricity will notably outpace inflation and assume 100% of the power generated by the panels is fed to the grid.

They all said they had to notify their insurance when getting installed and it added a small amount.  I didn't probe on the exact premium increase, but it didn't sound like very much.  One said adding the deck was more.

I will say that the Tesla install looks much nicer than the others.  Not sure what the hardware or panel difference is, but I'd pay more for it. 
 

Offline Poe

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #88 on: June 19, 2018, 04:54:30 am »
Found some USA data that's kind of close..

Unfortunately, like most of these "...worth it?" solar reviews, their math is screwed up. 

In this one, they misinterpret the kWh rate to be 39 cents, with an ROI of eight years. 

Luckily they posted their bill.  It shows they get billed at 11cents for the first 374kWh then 31 cents after that.  Taxes and fees increase it, but some are fixed prices.  So his solar install's first kWh nets him roughly 20 cents.  Then as his bill decreases, the effective rate drops to ~11cents per kWh generated.

So his best case ROI is actually closer to 16 years.  Realistically ~21years.  33 years without the tax credit. 

Newer panels are better, but since that's not the entire cost of the total install, and other costs have increased or been added, the ROI doesn't appear to have improved much.


 

Online metrologist

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Re: EEVblog #1086 - 5 year Solar Power Payback?
« Reply #89 on: June 19, 2018, 03:14:39 pm »
Tell your neighbors to hire more summer kid labor to clean the panels and the output might increase. Don't worry about those 1099 forms, they surely won't fall off the roof and injure themselves either...and if they did, I'm sure your home insurance would cover it. Or if they're not over 60, just climb up themselves, that's free...or cheaper than a fund manager? :-//
 


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