On-grid domestic battery storage

lisyloo

QrizB said:

lisyloo said:

There's a shell tarrif (i think) that gives you up to £150 off if you export electricity back to the grid.

This one?

https://www.shellenergy.co.uk/smart-home/solar-battery

"Our Solar Storage tariff is currently unavailable. Please check back later for more information."

yes that's it.
So if I bought a battery on the basis of getting a discount then I'd have to stick to a tarriff that offered that feature.
At the moment that one if not available and neither are any good deals but in general it would restrict the choice of tarriffs if you are banking on getting the discount to finance the battery purchase.

QrizB

lisyloo said:

... in general it would restrict the choice of tarriffs if you are banking on getting the discount to finance the battery purchase.

Yes, but that's an expensive battery and we don't know what Shell's tariff is so it might be an awful deal all around. (On the face of it, at £150 per year it would take 30 years to pay back the £4500 cost of the battery.) Most people don't fund their batteries that way.

lisyloo

QrizB said:

lisyloo said:

... in general it would restrict the choice of tarriffs if you are banking on getting the discount to finance the battery purchase.

Yes, but that's an expensive battery and we don't know what Shell's tariff is so it might be an awful deal all around. (On the face of it, at £150 per year it would take 30 years to pay back the £4500 cost of the battery.) Most people don't fund their batteries that way.

ok, how do most people make it pay?
by using the stored electricity and reducing the consumption they have to pay for?
How much would they expect to save each year and how many years to repay the battery?
Are you saying I also need to look for a cheaper battery?

So I guess this works better for people who generate solar but have a low % of using it, that's probably not us given we WFH.

Verdigris

Solar is probably the best utilisation but charging cheaply, on a TOU tariff, might pay off if you fully charge and discharge every day. You'd need a smart meter for the latter, of course.

QrizB

lisyloo said:

QrizB said:

lisyloo said:

... in general it would restrict the choice of tarriffs if you are banking on getting the discount to finance the battery purchase.

Yes, but that's an expensive battery and we don't know what Shell's tariff is so it might be an awful deal all around. (On the face of it, at £150 per year it would take 30 years to pay back the £4500 cost of the battery.) Most people don't fund their batteries that way.

ok, how do most people make it pay?
by using the stored electricity and reducing the consumption they have to pay for?
How much would they expect to save each year and how many years to repay the battery?
Are you saying I also need to look for a cheaper battery?

So I guess this works better for people who generate solar but have a low % of using it, that's probably not us given we WFH.

Let's start with the basics. How big is your PV system and how many kWh per year do you generate? Given that you've owned it for 8 years, are you on a FIT with deemed export? And how much electricity do you buy from the grid, not just over the year but monthly from April to September (the good solar months)?

lisyloo

PV system is 3.9
Generation is between 3500-4000 per year

yes its deemed export 50%

Apr 594
May 591
Jun 380
Jul 499
Aug 485
sep 400

so about 3000 total over the summer months

QrizB

lisyloo said:

PV system is 3.9
Generation is between 3500-4000 per year

yes its deemed export 50%

Apr 594
May 591
Jun 380
Jul 499
Aug 485
sep 400

so about 3000 total over the summer months

Apologies in advance, this rambles a bit.

Looking at your system size and scaling the performance of mine to match, you might expect to generate 130kWh/month in Dec and Jan, but 350+kWh per month from March to September (3/4 of your annual generation in those 6 months). If you're exporting half of that (and that's a guess, pending better numbers) there's scope to capture some in a battery and offset that against your electricity bill. The challenge is making that economic.

That 7kWh Solis system a page upthread was £3500 (plus fitting). Let's assume usable capacity is 6kWh. If we can cycle that much electricity through it, 180 days a year, that's 1080kWh, which at 20p/kWh is £216-worth of power you won't have to buy from the grid. Unfortunately £216 goes into £3500 sixteen times, so that's a 16-year payback (and assumes there's 180kWh/month available to rescue).

The sonnenBatterie you first mentioned is 4kWh and £4500. 4kWh/day x 180 days is 720kWh, at 20p/kWh worth £144. Even adding Shell's special £150 credit only gets you to £294 pa and a 15-year payback time. Simiular to the Solis plus you're tied to Shell (and hoping they keep the special tariff for 15 years).

lisyloo

Thanks for taking the time to explain that to me.

Spies

This has got to be some of the worst advice I've seen lately, his calculations don't include an EV and yet Octopus Go isn't available any longer without proving EV ownership.

I used to like his channel but spreading misinformation like that could cause some very costly mistakes for people. 

https://youtu.be/_T0vahG6JPU

arty688

Yes, watched yesterday thinking of unsubscribing , even on my most optimistic man maths day my figures are nowhere near. I just wonder how much Givenergy paid him or maybe he is just stupid?