Author Topic: EEVblog #724 - Home Solar Power System Analysis & Update  (Read 46383 times)

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Offline SeanB

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Re: EEVblog #724 - Home Solar Power System Analysis & Update
« Reply #50 on: March 16, 2015, 03:40:59 pm »
I just looked at my electric bill, and the price I pay is $0.10 per kWh. As the suppliers currently do not allow a feed in tarrif or even grid tie, you cannot do a solar system legally, unless you go like Martin Lorton did and go with batteries and partly off grid.

I just use a small 30w panel and a 12V 60Ah battery, to do lighting and other low power loads. Helps when load shedding is active and I estimate it has been worth it, even though I have had to buy a new 60Ah battery this year to replace the aging one in the system. I paid more for the battery than what the system originally cost as used.
 

Offline tcleavela

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Re: EEVblog #724 - Home Solar Power System Analysis & Update
« Reply #51 on: March 16, 2015, 04:22:35 pm »
If you want to get into solar but are put off by the price or size, think hot water. Many homes have electric water heaters with two elements.  Just 300W of panels is enough to make a serious dent in electric useage of this device.

Heating water consumes around 40% of my bill. I've considered a passive system but this is an intriguing alternative. Even if it cost 800 bucks it'd pay off in about a year.
 

Offline DanielS

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Re: EEVblog #724 - Home Solar Power System Analysis & Update
« Reply #52 on: March 16, 2015, 04:23:43 pm »
Yeah, I have to say Dave that I would expect you of all people to have some battery storage hooked up. It seems ridiculous that your electrons are worth so much less than the grids electrons.
Its complex in Australia as you generally cannot have batteries that are interconnected with the grid, they need to be a changeover system which adds some significant complexity.
I would not expect batteries to make any difference here: the inverter already needs the line voltage reference to lock phase with so it can adjust its output accordingly to export power and needs to shut down if power fails since it cannot drive the whole neighborhood including the local distribution transformer and whatever might lie beyond that on its own without tripping over-current or under-voltage protections. Regardless of what the exported power source is (PV, battery, generator or whatever else), export needs to stop when loss of mains is detected.

Adding batteries changes nothing to the inverter's operation aside from smoothing out PV output variations and enabling time shifting of PV energy use. You should only need a switch-over/disconnect if you want to be able to use the panels and batteries to operate off-grid during outages.
 

Online German_EE

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Re: EEVblog #724 - Home Solar Power System Analysis & Update
« Reply #53 on: March 16, 2015, 05:06:55 pm »
A friend of mine has a solar power system that works rather well, the principle is as follows:

Assuming incoming solar power

1) Are the accumulators charged? This is important because the whole house runs off these accumulators via sine wave inverters.

2) If the accumulators are charged is there hot water? He has two massive insulated water tanks and this is the next destination for the power.

3) (Summer) Dump excess power into the jacuzzi or air conditioning (Winter) Dump excess power into the under floor heating which is done using resistive mats.

In 2014 his annual power bill was 122 Euro.
Should you find yourself in a chronically leaking boat, energy devoted to changing vessels is likely to be more productive than energy devoted to patching leaks.

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Offline rolycat

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Re: EEVblog #724 - Home Solar Power System Analysis & Update
« Reply #54 on: March 16, 2015, 05:37:17 pm »
A friend of mine has a solar power system that works rather well, the principle is as follows:

Assuming incoming solar power

1) Are the accumulators charged? This is important because the whole house runs off these accumulators via sine wave inverters.

2) If the accumulators are charged is there hot water? He has two massive insulated water tanks and this is the next destination for the power.

3) (Summer) Dump excess power into the jacuzzi or air conditioning (Winter) Dump excess power into the under floor heating which is done using resistive mats.

In 2014 his annual power bill was 122 Euro.

The system sounds exceedingly expensive - what was the capital cost and the likely repayment period?
How long do these accumulators last before requiring replacement?
 

Offline Seekonk

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Re: EEVblog #724 - Home Solar Power System Analysis & Update
« Reply #55 on: March 16, 2015, 06:44:58 pm »

Heating water consumes around 40% of my bill. I've considered a passive system but this is an intriguing alternative. Even if it cost 800 bucks it'd pay off in about a year.
[/quote]

It will take more than $800.  I have a add on heat pump that cuts electrical usage in half and that runs about $1,000. They all have a COP of about 2 if you look in the fine print. Most hybrid water heaters like GE cost $1,600 and in ten years it has to be replaced.  It's like buying yourself a job.  Supplementing with PV solar is not a bad payoff compared to HPWH cost and it will extend the life of the compressor.  A tempering valve is needed with a large PV system so you can run the tank up to 145 degrees.  Lot easier to run a wire in an existing house than tubing and it will never freeze.  No maintenance on pumps.
 

Offline nixfu

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Re: EEVblog #724 - Home Solar Power System Analysis & Update
« Reply #56 on: March 16, 2015, 06:50:57 pm »
It seems much more expensive now for solar installation.  I know a few years ago the Chinese were apparently flooding the market with panels at below cost, and the US has stopped that I think so costs maybe have gone up.

It looks like it would be $10-15k US for a comparable system in the USA, which is much more than the ~$5k AUS you said you originally spent.

I also wonder if there have been any improvements in panels since the few years that Dave installed them.
 

Offline linx310

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Re: EEVblog #724 - Home Solar Power System Analysis & Update
« Reply #57 on: March 16, 2015, 07:43:24 pm »
I work in the solar water industry.  Its not as sexy as PV but your money goes a lot further if you live in a climate with lots of sun.

The solar water systems we have installed here in Texas will cut your water heating bill big time if you uses an electric water heater.
 

Offline LabSpokane

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Re: EEVblog #724 - Home Solar Power System Analysis & Update
« Reply #58 on: March 16, 2015, 08:04:26 pm »
The home solar is fantastic. What would even be better are Solar Freaking Carports to charge your EV at work. For most  8-5 workers, it's an excellent match between resource and demand.
 

Online PA0PBZ

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Re: EEVblog #724 - Home Solar Power System Analysis & Update
« Reply #59 on: March 16, 2015, 09:37:40 pm »
When you include 2 summers and only one winter in your calculations wouldn't that show a bit optimistic payback time?
Or more generally: shouldn't you base payback calculations over full year periods? Anyone want to do the math?

Keyboard error: Press F1 to continue.
 

Offline Seekonk

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Re: EEVblog #724 - Home Solar Power System Analysis & Update
« Reply #60 on: March 16, 2015, 10:43:40 pm »
I get tired of all these people that talk about panels under a buck a watt.  Where are they and would you want to buy them?  Just saw an article about the Australian Govt. Investigating cheap Chinese panels that are failing after three years and that they paid a subsidy for.  With UL, shipping, mounting and wiring there are no cheap panels.
 

Offline wemme

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Re: EEVblog #724 - Home Solar Power System Analysis & Update
« Reply #61 on: March 16, 2015, 11:04:48 pm »
Thanks for posting Dave, the Payback schemes just went the same way in New Zealand.
People are installing timers on their hot water cylinders to delay them until the solar power is available but even this is pretty half arsed.
 

Offline LabSpokane

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Re: EEVblog #724 - Home Solar Power System Analysis & Update
« Reply #62 on: March 16, 2015, 11:07:44 pm »
I get tired of all these people that talk about panels under a buck a watt.  Where are they and would you want to buy them?

Right here:  http://www.eco-distributing.com/Solar-Panels_c_150.html

Many of them are polycrystalline and good quality.  It's not just the crappy thin film panels that are less than a dollar/watt now. Eco is a legit company, I have purchased a couple panels from them. 

Also, I think one might even get the higher end panels at sub $1/W if you call and purchase in pallet quantities.  That's not really an unrealistic plan if you go in with neighbors or do a joint community solar project. 

What you *can't* buy so far in the US is under a buck a watt *installed*  - even on a utility basis so far.  So, the new focus in solar is getting the "balance of plant", permitting, and installation costs under control. 
« Last Edit: March 16, 2015, 11:12:26 pm by LabSpokane »
 

Offline tombi

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Re: EEVblog #724 - Home Solar Power System Analysis & Update
« Reply #63 on: March 17, 2015, 12:00:33 am »
Hello,

I'm one of the lucky people Dave mentioned in that we installed a 1.5kW system under the 60c tarriff. The vendor even offered terms so it cost $120/month for two years to pay off and interestingly, mine generates around 5kWh per day on average which covered most of the monthly cost. So it pretty much paid itself off in 2 years.

At the same time I arranged for a similar system to be installed at the sailing club where my kids sail. I've had no problems with mine but the one at the club has had long periods of outage.

The problem is the club is on a peninsula and the voltage can vary from 230v to over 260. The Sharp inverter's maximum is 260 so after that it stops pushing power into the grid. Unfortunately this would happen at about 10 am when everybody has gone to work and when when the sun is in the sky. It took a lot of calls to the power company but they eventually adjusted the system to mostly sort this out.

Even if I had to go to net metering, solar would make sense for me as unfortunately this house has a pool. I also work from home so I am running computers in the day.

We installed a heat-pump for water heating which reduced the water heating consumption from around 10kWh/day to 2.5kWh/day. This doesn't change the bill much though because it is running on Off peak (CL2) which is half price anyway. Here in Australia we have two off peak systems (Controlled Load 1 and 2) where 1 goes off only at night and 2 goes off at various times of the day when the grid usage is low. The heat pump is on CL2.

Not sure why Dave is paying a CL2 tariff when he has gas for hot water... Only had two meters so definitely no CL2.

The pool runs low speed pumps to reduce consumption but it is still bad (200W for 12 hours a day).

Tom
 

Offline nowlan

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Re: EEVblog #724 - Home Solar Power System Analysis & Update
« Reply #64 on: March 17, 2015, 12:09:07 am »
It looks like it would be $10-15k US for a comparable system in the USA, which is much more than the ~$5k AUS you said you originally spent.
I think most of the panels here are subsidized via Renewable Energy Certificates. Link
 

Offline mtdoc

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Re: EEVblog #724 - Home Solar Power System Analysis & Update
« Reply #65 on: March 17, 2015, 12:11:06 am »
I get tired of all these people that talk about panels under a buck a watt.  Where are they and would you want to buy them? 

HERE and HERE

Solar panels are a commodity item now. All of the major manufacturers produce quality panels with similar warranties (20-25 yrs).

You can pay a premium for certain "top of the line" panels but you'll get very little benefit - maybe slightly better efficiency and workmanship  But with panels so cheap, it almost always makes sense to just buy a few more panels rather than pay for more expensive panels.
« Last Edit: March 17, 2015, 12:12:45 am by mtdoc »
 

Offline darrenb

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Re: EEVblog #724 - Home Solar Power System Analysis & Update
« Reply #66 on: March 17, 2015, 12:19:46 am »
We live a couple of km's from Dave in Castle Hill and installed our 2kw system in June 2010 when the government was offering the 60 cents per kWh gross feedback that Dave was talking about.

At the time it was easy to calculate that at 60 cents per kWh a system would pay for itself in a few years and there was a general rush to have a system installed.

Our 2kw system with inverter cost $2,500 installed with a 2kw inverter.  We had to pay an additional few hundred dollars to have the system wired into the meter box.  We didn't go for any upgrade options but the system has been reliable so far with no reduction in output.

I have all the figures since June 2010.  The system has made on average 7.4 kWh per day from installation until now.  Our electricity bill has gone from over $2,000 per year to about $100 per year.  In the warmer quarters we usually end up with a negative bill and the credit is carried through to the winter months which usually use up any credits that we have accumulated.

On our last bill we used 1205 kWh of general electricity at 18.93 cents per kWh and 732 kWh of off peak (hot water) electricity at 6.31 cents per kWh.  The solar panels made 848 kWh at 60 cents per kWh.  The final figure on the bill was that the electricity company owes us $141.80.

This was a crazy system by the goverment but it did kick start the solar industry here.  The system was guaranteed for seven years from when it commenced and will end at the end of 2016.  I'm not certain what we will do then (or before) but a timed heat pump driven hot water system which can use solar during the day looks like an obvious upgrade.
 

Offline mtdoc

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Re: EEVblog #724 - Home Solar Power System Analysis & Update
« Reply #67 on: March 17, 2015, 12:30:00 am »
It seems much more expensive now for solar installation.  I know a few years ago the Chinese were apparently flooding the market with panels at below cost, and the US has stopped that I think so costs maybe have gone up.

It looks like it would be $10-15k US for a comparable system in the USA, which is much more than the ~$5k AUS you said you originally spent.

I also wonder if there have been any improvements in panels since the few years that Dave installed them.

True $5k for a 3 kW system is a good deal. I don't know how it works in Australia but in the US several companies have "lease" type installation agreements where they are able to claim  the 30% federal tax credit so the homeowner's installed cost is similarly low.

Panels in bulk are purchased at near $0.50 per watt . Depending on the size of the system, a strict grid tie system should come in at under $3 per watt.

And as far as I'm aware, no major improvements in commercially available PV panels in the last few years.
 

Offline cosmicray

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Re: EEVblog #724 - Home Solar Power System Analysis & Update
« Reply #68 on: March 17, 2015, 12:55:26 am »
I get tired of all these people that talk about panels under a buck a watt.  Where are they and would you want to buy them? 

HERE and HERE

Solar panels are a commodity item now. All of the major manufacturers produce quality panels with similar warranties (20-25 yrs).

You can pay a premium for certain "top of the line" panels but you'll get very little benefit - maybe slightly better efficiency and workmanship  But with panels so cheap, it almost always makes sense to just buy a few more panels rather than pay for more expensive panels.
The LG MonoX that Dave mentioned are listed on that first link, then click 24V. They are roughly priced at $2/watt.
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Offline poida_pie

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Re: EEVblog #724 - Home Solar Power System Analysis & Update
« Reply #69 on: March 17, 2015, 01:11:12 am »
I have a self built system, 3kW peak, batteries, inverter, 240AC changeover switch.

aims:
to replace some power usage each day.
The amount of power available on any day is indeterminable and also could vary from 1 kWhr to 20kWhr
depending on season and weather.
IF insufficient power available from solar, use street power for balance required.

facts here in Melbourne:
$0.31/kWhr for electricity from any supplier.
approx 4.5 hours sunlight per day average over a year.

facts world-wide in modern Western economy households:
short high peak electricity loads on top of a steady, low power base load.
My house has a base load of 600-800W which is present 24 hours a day.
This means 0.6 x 24 = 14.4kWhr base load plus short period peak power values.
My daily average energy usage is 17-20kWhr/day over entire year.
This 600W can easily be supplied from a well sized, efficient and decent inverter.
So I can save 3/4 of my energy usage by simply providing this 600W for 24 hours a day.

So, I chose a 3kW peak solar panel array, to feed a 15kWhr battery bank via a 60 Amp peak
charge controller (Tristar 60Ampr MPPT)
Inverter is Victron 3000 W peak, 2,500W continuous inverter. Max efficiency is at about 1/3 peak power,
this allows some headroom for growth.
system is based on 48V DC nominal battery.

Now, typically I obtain about 10 kWhr from the solar array, and this gets put into the battery with about
95% (NO! more like 80% edited 12:14pm) efficiency. Then during the day and following evening, I pull this power out of the battery via the inverter
to power SOME but NOT ALL of the house power. I might use 9kWhr of inverter power, which I do NOT have to buy from power company.

I have run separate general power outlets into most rooms that are all connected to the single 240VAC output
of the inverter, via other equipment.
I have all TV, DVD, computers, 4 fridges (don't ask, 4 fridges..that's insane)
kitchen toaster, kettle and pool pump etc all connected to the one 20A trunk line, supplied
via an 16A RCD contact breaker which is then connected to a change-over relay then the inverter.

The change over relay is the key to the entire system.
This can sense when one input stops and change over to the secondary input, and connect this
to the output. This allows me to provide 240VAC power for any period of time from the inverter and when not available, the relay will change over to use the street power as a substitute until the inverter powers up again.
All transparent and no need for human intervention.

Cost to me so far:
$3,600    solar panels
$2,300    Victron Multiplus inverter 48V/3000W
$700    Tristar 60A MPPT charge controller
$xxx    contact breakers, big-ass high rupture current DC fuses, wiring, etc
$400    Latronics change-over relay ACTS40
300Ahr 48V battery bank came free of cost. (ex Telstra mobile phone tower batteries destined for recycling)

I have data to show I am averaging about 8kWhr self supplied energy per day.
This is 8 x $0.31 = $2.48 per day saving of electricity. Does not sound much.
365 x $2.48 = $905 /year.
break even on investment approx 7 years
And we get to tell the foreign investors of our privatised power companies
to stick their product up their fucking arses. (value of this = $priceless)

Note well:
Electricity costs will increase in the future in large increments because they can.
After the faux privatisation of state electricity here in AUS, the Elec suppliers can name their own prices now
All in the name of "Free enterprise/competition/captured markets/corruption/what-have-you"
So my system will get better as the price of elec. rises as it must.

I chose a nominal 100V DC solar array, coming into the charge controller to charge a 48V nominal battery bank.
This optimises the I2R (resistance) losses in the cable from panels to the charge controller (15 meters x 2)
and it then permits the highest efficiency inverter, being 48V DC.
Your installation may require different design factors for optimum performance.

go for it if you have the $$$. No need for a complete stand alone off grid system.
You can make 3/4 of total savings possible at 1/4 the cost.

A full on off-grid system needs 5X the batteries, 4x solar panels, 2X inverter and changes to house lifestyle.
All for the final 1/4 savings. Not worth it unless you must go off-grid.
« Last Edit: March 17, 2015, 01:14:12 am by poida_pie »
 

Offline mtdoc

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Re: EEVblog #724 - Home Solar Power System Analysis & Update
« Reply #70 on: March 17, 2015, 01:16:50 am »
I get tired of all these people that talk about panels under a buck a watt.  Where are they and would you want to buy them? 

HERE and HERE

Solar panels are a commodity item now. All of the major manufacturers produce quality panels with similar warranties (20-25 yrs).

You can pay a premium for certain "top of the line" panels but you'll get very little benefit - maybe slightly better efficiency and workmanship  But with panels so cheap, it almost always makes sense to just buy a few more panels rather than pay for more expensive panels.
The LG MonoX that Dave mentioned are listed on that first link, then click 24V. They are roughly priced at $2/watt.

Yep.  And if you bought them for that price you'd be paying over twice as much to get 16% efficiency instead of 15% efficiency. Not worth it. Like anything else, there's a lot of marketing hype with solar panels.

Unless you are really limited on space it almost never makes sense to pay a premium for higher efficiency panels. In the case of the LG Mono X versus another panel - say a Sanyo panel at $0.71 per watt (15% efficiency),  the same sized array would take up minimally more roof space.

Some panels put out slightly closer to STC specs on average but the differences are very, very small. Mono (versus Poly) supposedly output better in cloudy, diffuse light conditions but head to head testing has shown this to be a very small effect.  Just installing 5% more array (at less than half the cost) would give you more output.

That being said, I'm doubt Dave paid that much of a premium for his panels since his entire system came in at less than $2 per watt installed.

Also - paying a premium for a top quality inverter (like his SMA) is worthwhile IMO.
 

Offline EEVblog

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Re: EEVblog #724 - Home Solar Power System Analysis & Update
« Reply #71 on: March 17, 2015, 02:07:50 am »
Yep.  And if you bought them for that price you'd be paying over twice as much to get 16% efficiency instead of 15% efficiency. Not worth it. Like anything else, there's a lot of marketing hype with solar panels.
Unless you are really limited on space it almost never makes sense to pay a premium for higher efficiency panels. In the case of the LG Mono X versus another panel - say a Sanyo panel at $0.71 per watt (15% efficiency),  the same sized array would take up minimally more roof space.

It's not about efficiency, it's about build quality and local warranty support.
It's a much safer bet that LG will produce better quality panels than WunHungLo on ebay, and they'll be around in 20 years time to use that warranty if needed.
That's why I paid more.
 

Online coppice

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Re: EEVblog #724 - Home Solar Power System Analysis & Update
« Reply #72 on: March 17, 2015, 02:54:36 am »
Yep.  And if you bought them for that price you'd be paying over twice as much to get 16% efficiency instead of 15% efficiency. Not worth it. Like anything else, there's a lot of marketing hype with solar panels.
Unless you are really limited on space it almost never makes sense to pay a premium for higher efficiency panels. In the case of the LG Mono X versus another panel - say a Sanyo panel at $0.71 per watt (15% efficiency),  the same sized array would take up minimally more roof space.

It's not about efficiency, it's about build quality and local warranty support.
It's a much safer bet that LG will produce better quality panels than WunHungLo on ebay, and they'll be around in 20 years time to use that warranty if needed.
That's why I paid more.
So, you think Panasonic, who now own Sanyo, are more likely to go out of business than LG? Could be, in these rapidly changing times. More importantly, perhaps, is who is actually providing these warranties. People often think they have a warranty from a huge stable corporation that can be relied on, only to find out their warranty agreement is with a subsidiary that gets closed down. This happens a lot with home construction.
 

Offline zapta

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Re: EEVblog #724 - Home Solar Power System Analysis & Update
« Reply #73 on: March 17, 2015, 02:57:29 am »
I've never had any money to invest, so maybe I'm way off base here.....
But I get the impression that it would make more financial sense to invest that $5k in the stock market.
Eight years of compounding savings versus just getting your money back (Does this equipment retain its value on the second-hand market or would people be silly to buy used?) then hoping you can turn a profit near the end or after the warranty has expired.

Dunno.  Just thinking out loud.

You are thinking well.  It's called opportunity cost, an important part of every serious investment analysis. 'the value of my house went up' doesn't necessarily mean that it was an efficient investment.

http://en.wikipedia.org/wiki/Opportunity_cost
Drain the swamp.
 

Offline mtdoc

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Re: EEVblog #724 - Home Solar Power System Analysis & Update
« Reply #74 on: March 17, 2015, 02:58:46 am »
Yep.  And if you bought them for that price you'd be paying over twice as much to get 16% efficiency instead of 15% efficiency. Not worth it. Like anything else, there's a lot of marketing hype with solar panels.
Unless you are really limited on space it almost never makes sense to pay a premium for higher efficiency panels. In the case of the LG Mono X versus another panel - say a Sanyo panel at $0.71 per watt (15% efficiency),  the same sized array would take up minimally more roof space.

It's not about efficiency, it's about build quality and local warranty support.
It's a much safer bet that LG will produce better quality panels than WunHungLo on ebay, and they'll be around in 20 years time to use that warranty if needed.
That's why I paid more.

Dave-  I'm not talking about "WunHunLo" panels from eBay. Look at the link I posted - HERE.  I'm talking about top brand, top quality panels like Sharp, Canadian Solar, etc that are priced less than 1/2 the price of the LG panels at that particular  vendor - who BTW is one of the largest in the US..

I have no idea how much of a premium you may have paid. And you're right that local warranty support could be important (though PV panel failures are very rare).  Paying a small premium may be worthwhile in some cases. But in my experience and from talking to many others who have installed PV systems - the workmanship of all the top brands is similar.

Again - any extra you paid might have been worth it - I don't know the specifics of what your choices were.  In any case at $5K for a 3kW system with a SMA inverter - you did well, regardless of the panels.

My comments were only referring to the >2:1 price differential from that particular vendor and the general point that paying a lot extra for one top brand over another is generally not worth it.  Just my $0.02
« Last Edit: March 17, 2015, 03:00:41 am by mtdoc »
 


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