The future?

DOBLY

How your smart home could generate, store and sell energy

Buy & store Economy 7 electricity locally to use and sell excess sell back to the grid later?
Can this work / be viable with current batteries?
Interesting!

bardel

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.

MikeRM

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.

bardel

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!

spinaltap

Last year, eOn quoted £14k for 13 integrated PV panels plus 2 x storage batteries. My projected annual electricity bill was <£20.

MikeRM

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.

MikeRM

PS - I see they have just bumped up the price again! £8350 plus installation now - I guess I just got in in time!

spinaltap

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.

MikeRM

Is the Powerwall worth it compared to the competition? BYD sell theirs for literally half that price, for example.

MikeRM

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.