The future?

Bit late to this post but...!

In theory seems like a good idea, but surely people will buy batteries to service their own daytime electricity needs using power purchased at night time before they consider selling it back to the grid?

On top of which, at the current sell back rates and the modest storage that we would have individually in terms of battery storage, I can’t see how it would be economical?

Definitely think storing night time electric for daytime use is a winner though. Planning to do just that when I add batteries in the coming 1-3 years.
 
I understand that the current payback rate is about 4-5p per kWh. At that rate it definitely isn't economic. Whether using a home battery to charge at cheap rate and supply your peak rate demand is another matter. I'm about to order a single Tesla Powerwall 2, having done a lot of analysis using my Owl intuition data. I have a 4kW solar array. I've managed to simulate up to a week's Powerwall performance, assuming charging at night rate and day solar surplus. The latest Powerwall 2 software is quite clever and is able to use next day's forecast solar radiation to decide how much to charge at night. It's usually pretty accurate but occasionally gets it wrong, not surprising given our rather variable UK weather. I've checked this using data from a friend who already has Powerwall 2's.

It works out that for my situation the power wall can generally supply all my peak rate demand without and additional solar input, so peak rate usage should be fairly minimal. Night rate usage will be a bit higher, but solar charging keeps this increase fairly low. In terms of economics it's fairly marginal. I'm assuming a 15 year useful battery life for the payback calc. It's highly dependent on two factors:
1 - future energy price inflation
2 - getting the lowest possible night rate tariff in the future.

I've recently signed up to the EDF Blue+ Price Freeze Feb 21 tariff which is 5.4p/kWh low rate and 23.75p/kWh peak rate. At this very large split I should save about £700 per year against £1300 without the Powerwall. It's still the best deal for me without the Powerwall as I have an electric car and use 3 times as much Low compared to Peak rate energy. Taking loss of investment return into account I should be £200 p.a better off over 15 years with 6% p.a. electricity price inflation. That's the annual average inflation over the last 15 years. Suggestions are that it might be higher in the future in which case the return will be better. However, if the best available Low tariff rate rises significantly and the gap between Low and Peak rate closes it could easily make a loss. On current industry average rates of about 10p/kWh Low and 18p/kWh Peak it's very marginal to loss making.

If one installs more solar (without FIT payback) expecting to make on future export payback it still isn't economic at the currently available rates. Nor is installing more battery capacity. It's important to balance solar and battery capacity against house demand.

It's all rather a gamble. The price of the Powerwall 2 has risen significantly over the last year, which doesn't help, although the latest Gateway 2 controller is certified for power outage backup, which can be rather useful and also means the solar will keep working during a power cut.

It would be interesting to hear about the economics from anyone who has already installed a Powerwall 2 or other batteries.
 
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Be interested to see an update on your progress over time Mike.

Our usage is significant. Roughly 30,000 kWh in the last year (fairly sizeable property with 15kW ground source heating). We’ve a 25kW solar array installed since December last year, but it’s amazing how variable the output can be from day to day at this time of year.

I’m hoping to add batteries in the next couple of years, but it does need to be a little more economical thank it seems currently. I do think that energy costs are only going to get worse though.

Glad to see that the Tesla has power cut backup in place now, I live in the countryside and we’ve had a few more power cuts in the short time we’ve been here compared to our previous suburban location. Seemed doubly painful that the solar panels were creating north of 20kW and I couldn’t use any of it!
 
Last year, eOn quoted £14k for 13 integrated PV panels plus 2 x storage batteries. My projected annual electricity bill was <£20.
 
Well I've just decided to order a single Powerful 2. As I said earlier, the payback is marginal. It's highly dependent on future electricity price inflation and, in my case, continuing to have a wide split between peak and night rate tariffs. It's also dependent on the initial cost and this is where I've been having reservations. The cost of a Powerful 2 has risen significantly over a year. firstly, the battery price went up. Then they introduced the Backup Gateway, resulting in another increase of £1000 with the marginal benefit, for most of us, that it provides power during a power outage. But the main stumbling block is the installation cost. Tesla indicate a figure of between £950-£2700 on the website. My installation is about the most simple. Bolt the Powerwall and the gateway to the wall next to the meter and wire it in to the adjacent meter board. So I'd been assuming a cost of about £1000-1200. The price of a single Powerwall 2 and Gateway is stated as £7900 inc 20% VAT , plus installation costs, on the Tesla website. I've had 2 similar quotes of around £10,000! Both said mine was a straightforward installation. I had a long discussion with Little Green Energy Company, and with Tesla, who admitted that the indicative installation prices on the website are dictated by head office in the USA and are not representative. I get the impression that Tesla are quite aggressive on costs with their installers and there have been a number of unsatisfactory installations at uneconomic prices. Apparently they have reduced their approved installer network and send a Tesla engineer round to inspect the installations now. I finally got a price of £9500, which, I was told, was a special deal after the boss had had a serious discussion with Tesla about their costs and indicative prices. Believe that if you will but I don't think it's all sales talk. They are saying that it's only really economic for them to install along with a solar installation. Anyway, I'm going to give it a punt at that price. As long as I break even over 15 years or don't make much of a loss I won't be too disappointed and it will safeguard against major price inflation - and help the environment.
 
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PS - I see they have just bumped up the price again! £8350 plus installation now - I guess I just got in in time!
 
While visiting the Elmsbrook site last week, I chatted with the site’s developer on why they hadn’t added storage batteries with the Solar PV panels that are installed on all their homes.

His response was that they had trialled Tesla, but the battery actually failed. Plus, Tesla required online monitoring of their battery from Tesla HQ. Elmsbrook chose not to subsequently install Tesla.
 
Is the Powerwall worth it compared to the competition? BYD sell theirs for literally half that price, for example.
 
Just googled BYD - 5.12kWh pack £3000 inc VAT, so to equate to a tesla 13.5kWh pack = £7900. Not sure if the BYD system has any control, like the Tesla Gateway. I suspect the Tesla Gateway is well ahead of the competition, so not much difference in price. I'm told the German sourced home batteries are more expensive than Tesla although I haven't investigated. Owning a Model S, I've been impressed with Tesla engineering, so I know which I'd go for.
 
Looking a bit further into the BYD batteries, in addition, you need an inverter, and control gear. I think that would work out more expensive than a Powerwall 2, assuming you can get anything equivalent to the Gateway2.
 
Just googled BYD - 5.12kWh pack £3000 inc VAT

You got fleeced.

BYD Battery-Box L14.0

That 14kWh so a little more than Tesla. £6,500 inc VAT, plus installation and an inverter.

More interesting though is the fact that they are modular. They do module wall mounted ones as well as free standing. So you can start with a smaller system and scale up over time, buying more modules as budget or need allows.
 
The Powerwall 2 can also be wall mounted and is modular, in that a second can be mounted in front of the first. A friend has 4 PW2's mounted in pairs, about 300mm deep (he has a very large demand!). The inverter is built into the PW2 which has just gone up to £6650 inc VAT, so the PW2 is cheaper although the single fixed size is 13.5kWh. That is about right with a 4kW solar array in a normal house, maybe a bit big if demand is fairly low. However, given that Tesla is competitive I think the main question is whether other systems have as advanced software control as Tesla. It depends what your requirements are. Fully off grid or backup only are different to a normal on grid house with solar, and individual power requirements are very important in sizing.
 
Looking at the Specs and warranty, the BYD is warranted for 10 years as is the Powerwall 2. But the Byd warranty is for 60% of original capacity whereas the Powerwall 2 is for 80%. That seems to tie in with the conditioning systems. The BYD is "natural cooling", passive air cooling, in other words. The Powerwall 2 has active liquid cooling. In other words the same as the Model S and Model 3 battery conditioning systems. It is maintained at the optimum temperature for charging. That is why the Model S, and by inference the PW2 have a much longer battery life than the Nissan Leaf, which has no active conditioning. My Model S has lost 3% in 4 years/50,000 miles and most of that was in the first few months, as is normal with lithium ion battery life. It's hardly changing at all now. I expect to get at least 15 years useful life from my Model S battery and probably much longer (I'll probably be dead or at least handed in my licence by that time!). I suspect the difference in warranty conditions is related to the conditioning systems. The PW2 can be expected to last a lot longer than the BYD. So it's like comparing apples and oranges.

Out of interest, here's a review of the PW2 and comparison with other batteries. It's from 2016 so a bit out of date but the cost per total warranted kW is shown to be lowest for the PW2 and highest for a BYD battery (not the L14.0)

Powerwall 2 Full Specs Reveal Cheap Storage And Limited Warranty
 
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Hmm, the Nissan Leaf has extremely long battery life. There are cars in the UK, taxis that have been rapid charged twice a day, every day and racked up 250,000 miles and they are still around 85% capacity. If anything the killer for batteries seems to be letting the car sit idle for long periods.

Obviously these are two different concepts. BYD let you build up the battery as required and you could refresh it by adding new modules as and when you desire. The idea that you don't have to buy the full 14kWh battery up front, you can start smaller and upgrade whenever you like, is appealing.

Competition is good. It looks like it's forcing Tesla to take a bath on Powerwall 2, which is obviously great for us. Shame they won't do it on the Model 3 as well.
 
Glad to hear that Nissan Leaf battery life is much better than all the reports I've read. Must be FUD! So Tesla are waisting our money incorporating battery conditioning systems? I note that Nissan have introduced some form of conditioning on the latest Leaf.
Nissan starts new program to replace old LEAF battery packs - Electrek
I always liked the Leaf, but reported battery life was one of the things that put me off. Of course, Tesla's have to survive the extreme temperatures in Death Valley and Norway - not a problem in UK.

Not sure about Tesla taking a bath on PW2. They keep putting the prices up! But I agree, competition is good.
 
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Glad to hear that Nissan Leaf battery life is much better than all the reports I've read. Must be FUD! So Tesla are waisting our money incorporating battery conditioning systems? I note that Nissan have introduced some form of conditioning on the latest Leaf.
Nissan starts new program to replace old LEAF battery packs - Electrek
I always liked the Leaf, but reported battery life was one of the things that put me off. Of course, Tesla's have to survive the extreme temperatures in Death Valley and Norway - not a problem in UK.

Not sure about Tesla taking a bath on PW2. They keep putting the prices up! But I agree, competition is good.

You need to do a bit more research to understand this issue, but I'll try to give you a summary.

Basically Nissan packs are fine when they are used regularly and not too heavily. So the taxi example is kind of the best case - mostly low speed around town, some sitting around waiting etc, and some rapid charges that warm them up but not too much.

People who do see more degradation tend to have older, relatively low mileage cars, that have been sitting around at high SoC for long periods.

The issue with the 30kWh packs was mostly due to a software bug that reported the SoH incorrectly. Nissan did an update to fix it and it appears to have worked. They also offer replacement packs although I don't think many have been sold, in fact I'm not aware of any in the UK. The car tends to reach EoL before the pack does.

Obviously active thermal management is a good idea for cars. I'm somewhat skeptical about Nissan's 62kWh packs because they lack it. For smaller packs they can get away with it, but the 40kWh was borderline and even with the software fix doesn't work all that well (lifetime TBD, it's too early to tell).

But home battery packs are a different kettle of fish.

They get cycled every day. Charging is relatively slow, discharge is relatively slow. Being indoors the ambient temperature is at least somewhat regulated. The BMS is free to limit charge and discharge as necessary.

Tesla are having problems getting their battery costs down at the moment, which is why they are taking a bath on them. For example, they really really don't want you to buy the base Model 3 because even with all the other downgrades the battery is still too expensive and they lose money on it. Panasonic has given up investing in the gigafactory and developing the battery tech because Tesla doesn't pay them enough already, i.e. they can't make any money.

The main issue they have is that they picked the wrong technology. They are making cylindrical cells, which are high reliability and can charge/discharge at high rates but also cost more. Other suppliers have mostly gone to pouch cells, the kind you find in mobile phones. They cost less to make and although you can't charge/discharge them as hard it's more than adequate for most cars.

In fact the cost is so much lower that pack manufacturers use simpler BMS and conditioning systems, and instead over-provision the packs more. So actually when you look at a BYD pack that says 14kWh usable, when new it will actually offer significantly more than that. People have found the same thing with cars, e.g. a "64kWh usable" Kona will offer over 66kWh usable when new.

In summary you have to be careful when comparing batteries from different manufacturers. The capacity rating is a nominal number and the kind of conditioning system in use doesn't really tell you much about reliability or expected lifespan.
 
Thanks, Comadose, you clearly know a lot more about Lithium ion batteries than me. I'm an engineer, not a battery expert, I can only go on the research I have read, and I try to use reliable citable sources rather than internet gossip where possible (not always easy!). You are certainly right that there is more to the battery life issue than conditioning. My understanding is that leaving a Lithium ion battery fully charged for a long period is bad for life, as you say. Because the Teslas have such large batteries it is rarely necessary to charge to full and Tesla advise using the car within an hour of a range charge to avoid just this situation. I habitually charge to 70% since I have read a technical article that indicated that keeping the state of charge between about 30-70% is best for longevity. 80% is OK too but I don't usually need that much. On the Nissan Leaf, please correct me if I'm wrong, but I understand it's not possible to control the level of charge and it will always charge to 100% (unless you unplug it presumably). Since Leaf's, particularly early ones, have a much smaller battery and rather limited range they would be rather difficult to use in practice if they were not full before starting a journey of any length so I assume many Leaf's do often sit idle at 100% for long periods, hence the quoted limited life of Leaf batteries.

You mention taxi's and interestingly, the Tesla's that have already achieved very long battery life (>90% after 500,000km) are reported to be the Tesla taxi's at Amsterdam airport.

Whether Tesla made a mistake using the cylindrical 18650 cells is debatable. They had to make commercial production decisions back in 2012, or rather earlier for the Roadster, and I think battery technology has progressed rapidly since then. Personally I think it was sensible to use proven technology for the Model S. Can you quote verifiable pier reviewed sources that show that pouch cells are better (or more cost effective) for the high instantaneous demand/high charge rates required for electric cars (especially powerful ones like Tesla/Audi/Jaguar) than the ones Tesla currently uses. Battery production is clearly critical and I believe Tesla uses more material resources than anyone else, of a relatively limited supply of rare metals etc. It seems to me that they have been very far sighted in both developing the Supercharger structure and the Gigafactory(s). At least it gives them the best control over supply of batteries if not raw materials.

Despite the frequent press about 'Tesla killers' I don't see that the established car manufacturers (with the possible exception of Nissan? - but different market) have the incentive to volume produce electric cars over ICE cars. Very perceptive article about disruptive technology here:
https://www.hamidshojaee.com/post/184522555004/teslas-autonomy-day-the-stock-short-sellers-and [hamidshojaee.com]

Home batteries are probably a different ballgame since there are a number of battery suppliers directly involved in producing and selling them, so Tesla has direct competition in this area.
 
I wouldn't say Tesla made a bad decision when they initially went with cylindrical cells, it just turned out that way in the long run. It's always tricky to know when to abandon something you invested a lot in. Interestingly though Panasonic seem to have seen the writing on the wall a while back, as their new plant in China is focusing on pouch cells.
 

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