Solar & Powerwall 2

old.Osy

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We're putting in a 10Kw system soonish, 8kw Fronius Gen24 to power it. No battery.

Total cost, 8600 GBP, government covers 3500, so pocket cost of approx 5100.

Net metering is a thing, as are credits - we'll see what that does to the bill in time. We'll be selling energy back to the grid, but it's not as straightforward as it may seem, as we run 3-phase, and the inverter can only do 3KW instant per phase, so if I have a bunch of appliances on a single phase drawing more than 3KW instantly, I will be pulling the difference from the grid, even if overall the system produces more than we actually spend.

What that means is I will have to careful balance out the AC units and the other major consumers (dish, wash, dryer, kettle, etc), in order to mitigate the above as much as possible. So that's some re-wiring in the future, potentially.

I specifically wanted Fronius because of the local API and no cloud nonsense (you can go via cloud if you want, but it's opt-in) - I'll plug this into HA (Home Assistant) locally.

Huawei, Growatt, Deye are a few brands which installers push out here, but they're all cloud locked. I hate that.
 

Scouse

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How come no battery m8? Doesn't that make most sense for overnight power etc?
 

old.Osy

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How come no battery m8? Doesn't that make most sense for overnight power etc?

With the current battery tech and costs, it really doesn't make sense financially. Besides, our consumption stalls once it's dark out, with some exceptions.

I hope with the energy credits racked during day time to cover the extra pull from the grid, so that it's net.
 

Embattle

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Indeed as originally stated I didn't expect the battery to make a return on investment due to the cost of the Tesla Powerwall 2 and its installation being nearly £8000, after 4 years and 6 months the battery has done the following:

Screenshot_20240512-221941.png

So if I use the figure of 4.4 MWh and convert that to 4400 kWh then use an average of 20p per kWh to buy that electricity then the total saved is £880.

There are other ways to improve the return, so also as mentioned in one of my previous posts you could fill up the battery with cheaper night rates but a couple of issues arise because I can't use both an export tariff and take advantage of lower night rate tariff to fill the battery. The second issue is you just wouldn't use the cheaper night rates during the summer periods when the battery easily fills. Naturally, the other advantage is it does act as a backup device as well.

The solar survey is on Wednesday for the 2KW extension.
 

Scouse

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Oof. A 36 year payback on the tesla :/

What's yer current profit against cost for your solar @Embattle ?
 

Embattle

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Oof. A 36 year payback on the tesla :/

What's yer current profit against cost for your solar @Embattle ?

Well using last year:

1000011880.png

Now let's pretend the battery doesn't exist and split its power 50/50 because without the battery we would probably use the solar more wisely in the home.

So the average price per kWh in 2023 was 27p, the average export was 15p.

Home - 0.27x2875 = £776.25
Export - 1260x0.15 = £189

So the total savings last year would probably of been in the region of £965.25 if we never had a battery. The high price of electricity of the last couple of years really boosts savings, but you'll easily cover the cost of solar over the lifetime of panels even with the cost of a replacement inverter.
 

Deebs

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I am going to have solar installed and more than likely a battery as I have a datacenter's worth of electronics/computers on 24hrs a day. My electric bill is huge so I don't think it would take long to recover the cost but one question, in the event of a power cut/surge (at night) the battery acts quick enough to keep everything running (ala poor mans UPS)??
 

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