Does anyone have a Tesla Powerwall (or another type of battery system)?

[Halcyon]

I've been strongly considering installing a battery system to supplement my 5 kW solar system on my home. During the week, most of my usage is in the evenings or at night. I'm on a net metering system. At the moment I'm getting 6.7c per kilowatt hour back from my energy supplier (soon to go up to 12c/kWh) but when the sun goes down, I'm buying it back for something like 23c/kWh. My household consumption averages about 20kWh per day. During autumn/winter, I generate about 6.7kWh per day in excess electricity which goes back into the grid.

I've been getting a few quotes together for Panasonic, LG and Tesla Powerwall systems. So far, Tesla's offering looks quite good. They guarantee 13.5kWh of usable capacity (to 100% depth of discharge, which I'm guessing they are achieving by adding slightly more capacity to the system), the system is scalable (where as the Panasonic one isn't), they guarantee 70% capacity after 10 years with unlimited discharge/charge cycles (in a residential installation) and they offer the option of using it as a giant UPS for your house if the mains grid goes out.

Does anyone have any thoughts, opinions or experiences they'd like to share?

[kaz911]

subscribing

I'm interested in the opinions here as well.

[Halcyon]

Just in case anyone's interested, today I was quoted just under AUD$9000 for a 5.3kW Panasonic system which includes installation. This is the first quote I've got so far, I'll update this post as I get more information.

A couple of the other guys at work are also in the same boat as me, we're all doing our homework and collaborating.

Here is a little comparison table I've put together from what I've found out so far (obviously it doesn't go into any great detail and figures may vary):

	Tesla Powerwall 2	Panasonic LJ-SK56A
Initial Usable Capacity (kWh)	13.5	5.3
Max. Inverter Efficiency	90%	93%
Output (kW; Peak/Cont.)	7 / 5	? / 2
Warranty	10 yrs; Unlimited cycles*	10 yrs. @ 1 cycle per day
Guaranteed Energy Retention	70% after 10 years	60% after 10 years
Power Back-up Option?	Yes	Yes
Scalable?	Yes, up to 10 units	No
Dimensions (mm)	1150mm x 755mm x 155mm	1380mm x 966mm x 224mm
Weight	120kg	136kg
Operating Temperature Range	-20°C - 50°C	0°C - 40°C
Price (including install)**	TBA	~AUD$9000

Since I'm in Australia, everything is 240VAC.

* Unlimited cycle warranty only applies to solar self-consumption or backup supply. For all other applications, warranty covers up to 37.8 MWh of aggregate throughput.
** Cost shown assumes you have a pre-existing and suitable PV system and inverter.

Links to warranty documents: Panasonic LJ-SK56A, Tesla Powerwall 2

[tszaboo]

I believe the Powerwall 2 goes for something like 5000 USD + Tax + Zubehör. What I dont understand is: If you are on net metering, than why would this make sense? My parents (who live in a different country) are on net metering, so ever year, they read the consumption and production, they pay (or get back) the difference, and the pre-payment next year is based on that. Every year.
How does this work in Australia?

[VK5RC]

Unfortunately nothing to add myself but interested ++
Thanks.

[Red Squirrel]

I'd like to at some point.   Though I'm a bit old school, I'd do a telecom setup with lead acid batteries.  I feel they have less chance of exploding.  

Basically:

Hydro feed -> Rectifiers -> batteries -> large redundant inverters -> main panel

Add solar to the mix too and only run rectifiers when voltage goes below say, 48.0 volts.  Would float at 54 volts most of the time.   

All that would be really expensive though, so would need to figure out how fast it would pay for itself.   The biggest cost on the power bill is not the usage, but the delivery and all the other fixed fees.

How do the powerwalls work, do they have the power electronics built in to do what I described?  The inverter would need to be big enough to run the whole house, unless you want to split up your panel and pick and choose circuits.  Suppose that is a cheaper option as you can go with a smaller inverter, but it makes your electrical more complicated.

[Halcyon]

How do the powerwalls work, do they have the power electronics built in to do what I described?

My very brief understanding is that the original Powerwall 1 didn't have a built-in inverter, you needed to already have one which was compatible with the Tesla gear or you needed to purchase one. The Powerwall 2 has a built-in inverter and charge management circuitry which will interface with your existing solar inverter and switchboard.

[Halcyon]

If you are on net metering, than why would this make sense? My parents (who live in a different country) are on net metering, so ever year, they read the consumption and production, they pay (or get back) the difference, and the pre-payment next year is based on that. Every year.
How does this work in Australia?

Our meters in Australia are read (and billed) every 90 days and we don't pre-pay our power consumption*. It makes sense because a large amount of the energy I generate during the day is "wasted" back into the grid, then when people get home of an afternoon/evening (when the solar is generating almost nothing), lights/air conditioning/electronics etc... go on and I'm paying the electricity company for the power we consume.

If I can store the excess I don't use during the day when usage is minimal (consumed mostly by computers and the fridge), I can use what's stored in batteries at no cost at night.



* There are some retailers which allow customers to pay a smaller amount each month based on an average of previous usage. It's designed to prevent "bill shock" for those who can't budget.

[Jeroen3]

So, a Tesla Powerwall provides 40 MWh of storage over it's full life, approximately. It will cost you, ~15k, including solar, that is ~35 to 40 cents per KWh? Quickly at the back of the napkin.
Maybe even worse, on cloudy days it might not get a full charge.

Looking at this it is very expensive energy.

And, for the backup power function you'd need a mains breaker, correct?

[tszaboo]

If you have net metering, and it is 90 days, than I dont think it makes economically sense to install batteries. You basically just produce the energy during the day, and use it at night. Yes, in the summer (winter???) you generate more, but you would need to store that for more than 90 days. The network is the battery.

[Halcyon]

So, a Tesla Powerwall provides 40 MWh of storage over it's full life, approximately. It will cost you, ~15k, including solar, that is ~35 to 40 cents per KWh? Quickly at the back of the napkin.
Maybe even worse, on cloudy days it might not get a full charge.

Looking at this it is very expensive energy.

Based on the original Powerwall 1 (which had approximately half the capacity), the system would pay for itself within the 10 year warranty period. This was based on a 4KW PV system + Powerwall available in January 2016 for under AUD$15,000 and the average solar generation in Sydney AU on a 4KW system is about 15.6kWh per day (averaged across an entire year). Most parts of Australia have higher generation (the highest being Alice Springs at about 20kWh per day).

And, for the backup power function you'd need a mains breaker, correct?

No idea how this works.

[Halcyon]

If you have net metering, and it is 90 days, than I dont think it makes economically sense to install batteries. You basically just produce the energy during the day, and use it at night. Yes, in the summer (winter???) you generate more, but you would need to store that for more than 90 days. The network is the battery.

'

The problem is, the network pays me (currently) 6.7 cents per kWh I export, then when I get home, I'm paying 24.3 cents per kWh to get it back. As of July this year, power prices are increasing among most retailers.

Looking at my past power bill, I exported 599 kWh to the grid which earned me a $36.54 credit to my bill over 90 days.

The network is a pretty expensive "battery" in my opinion.

[tszaboo]

Then it is not net metering. In net metering, first they calculate the difference between the production and consumption for the period, and you only get payed for the excess production (usually with reduced feed in tariffs), or pay for the excess consumption (normal price).

So I'm going to assume that you have Power purchase agreement, not net metering.
Anyway, a back of envelope calculation: You have 15 cent difference in pricing. You make some 600KWh excess in a quarter. That is 360 dollars in a year, so ROI is about 25 years.

[Halcyon]

Then it is not net metering. In net metering, first they calculate the difference between the production and consumption for the period, and you only get payed for the excess production (usually with reduced feed in tariffs), or pay for the excess consumption (normal price).

We're talking about the same system. I'm not sure how you're getting confused?

The only other option is gross metering which is where everything you generate on your solar PV gets pumped back to the grid and you're paid a solar feed-in tariff for it. Years ago where I live, the feed-in tariff something like 40-60c/kWh. This is where gross metering made sense because you were exporting the power into the grid for more than you buy it back for (people with large enough systems actually had their electricity accounts in credit). They put an end to that pretty quickly after everyone started installing solar.

The default option now is net metering (and has been for quite a while), you'd be bonkers to keep an old gross meter these days.

Storage makes perfect sense if your feed-in tariff is significantly less than your import price. Yes you have to factor in the cost of the system over a period of time, but even with the old technology, if was quite easy to come out on top.

[tszaboo]

I'm sorry, but you are using the term "net metering" wrong. Maybe even the DSO uses it wrong. In net metering, if you export 10 KWh during the day, and buy back 10KWh during the night, you pay 0.

[Halcyon]

I'm sorry, but you are using the term "net metering" wrong. Maybe even the DSO uses it wrong. In net metering, if you export 10 KWh during the day, and buy back 10KWh during the night, you pay 0.

I don't think so. Here's some maths using my current rates:

Export 10 kWh = 67c credit
Import 10 kWh = $2.40 charge
Import - Export = $1.76 out of pocket.

As you said earlier, you have to take into account the lower feed-in tariff. In this example, the proceeds from my export don't equal or outweigh my total outlay. This is by definition what the word "net" means.

[tszaboo]

You said net metering. If you pay for selling 10KWH and buying it back, then you dont have net metering. its called Power Purchase Agreements. https://en.wikipedia.org/wiki/Net_metering#Comparison Please read this, and understand it. You are just using the term "net metering" wrong. What you have is not net metering.

[Halcyon]

You said net metering. If you pay for selling 10KWH and buying it back, then you dont have net metering. its called Power Purchase Agreements. https://en.wikipedia.org/wiki/Net_metering#Comparison Please read this, and understand it. You are just using the term "net metering" wrong. What you have is not net metering.

 

I'm not going to go back and forth with this. What I have in place is net metering, this is what it's known as in the industry and it's pretty universal. Rather than relying on Wikipedia, you can refer to any number of government and industry websites. The only other option is gross metering (which I don't have). You can go ahead and call it "silly sausage PV scheme" if you like, it doesn't change what it is. Anyway, moving on... this was not the point of this thread.

[tszaboo]

You said net metering. If you pay for selling 10KWH and buying it back, then you dont have net metering. its called Power Purchase Agreements. https://en.wikipedia.org/wiki/Net_metering#Comparison Please read this, and understand it. You are just using the term "net metering" wrong. What you have is not net metering.

 

I'm not going to go back and forth with this. What I have in place is net metering, this is what it's known as in the industry and it's pretty universal. Rather than relying on Wikipedia, you can refer to any number of government and industry websites. The only other option is gross metering (which I don't have). You can go ahead and call it "silly sausage PV scheme" if you like, it doesn't change what it is. Anyway, moving on... this was not the point of this thread.

There is:
Feed-in tariff
Net metering
Power purchase agreement

All relates to how the electricity meter is connected. Net metering has one, bidirectional meter, with one number on it, which can be negative. You have two meters. Its not net metering. Anyway, it is obvious you dont plan to correct your wording. I know, it is confusing. So yeah, moving on. you saw my estimation with the 25 year ROI?

[Halcyon]

Net metering has one, bidirectional meter, with one number on it, which can be negative. You have two meters. Its not net metering.

For what it's worth I have a single meter, then again, I haven't checked it in about a month, a second one could have mysteriously appeared? Who knows?

[Monittosan]

Any reason why you're not building your own powerwall?

[Halcyon]

Any reason why you're not building your own powerwall?

This field of electronics isn't my area of expertise. Plus I'm not licenced to touch/work on anything at 240v.

[tszaboo]

Net metering has one, bidirectional meter, with one number on it, which can be negative. You have two meters. Its not net metering.

For what it's worth I have a single meter, then again, I haven't checked it in about a month, a second one could have mysteriously appeared? Who knows?

Just a simple question. If you have one meter, you produce 10 KWh during the day turns in one direction, and use it at night, turns in the other direction, it will show 0 the next day, right? So you would pay 0. But you claim, that you have a more elaborate payment scheme. I guess you have more than 1 meters then? Maybe it is not even called net metering.

[Jeroen3]

"Net metering" with a reversing counter is only temporary. If they notice you have solar, they will issue you a new meter, with two counters.
Based on "the old meter is out of calibration".

Wikipedia has an excellent page on this, including image.

[NiHaoMike]

One of my projects is a small version of the Powerwall, about 1kWh and designed to be portable with the capability to full charge in 1-2 hours. It uses a pair of Nissan Leaf battery modules along with a hacked server PSU. Would probably use an ESP32 as the network controller, currently prototyping with a Raspberry Pi 3 but that uses too much power for the standby state.

Those who have some sort of battery system or even just an automation setup should take a look at Ohmconnect, which pays you to use less energy at specific times.