Check on battery only vs solar/battery thoughts

hugheskevi

Interested in any thoughts, especially about anything I have overlooked.

My electricity data:

• Total annual use: 5,500 kWh
• Of which 17-hour daytime use: 2,500kWh
• Of which 8 hour nighttime use: 3,000 kWh (this is optimised as much as I can)
• Max daytime use: 9kWh (with occasional exceeding of this, but very rare)

Currently I have neither solar nor a battery. I have an Electric Vehicle (car) which I drive about 7,500 miles per year and charge overnight. I have a very good energy tariff which ends on 17 January 2027 so I am starting to consider what I will do from mid-January onwards.

I think the best option based on tariffs as they stand today would be to install a battery of 10kWh or a little larger but not solar. I can charge the battery overnight and run the house on it during the day, using a tariff such as EDF's Go Electric to get 6.99p / kWh to charge the battery overnight and use that to power the house during the day.

Even if I did not get a battery, the Go Electric tariff still appears the best for my circumstances (although I haven't considered all the Economy 7 tariffs in detail, so there may be something a little better). I calculate that taking into account a 10% charge/discharge loss, I would save £572 per year on my energy charges if I install a battery. So the price of installation is key to determine whether it is worth it or not, probably needing a cost under about £4,000 to justify.

Solar appears prohibitively expensive given I can have electric at 6.99 p/kWh with a battery - although solar would provide protection against rising prices or withdrawal of cheap overnight electric. The risk of withdrawal of cheap overnight electric before realising savings, or of changes in the market that mean further changes are desirable before the payback period has been met, are the biggest risks to be aware of.

Does that consideration and conclusion sound reasonable?

Arunmor

We are already having that discussion:-

https://forums.moneysavingexpert.com/discussion/6683465/battery-only-anyone-got-such-a-system

hugheskevi

https://forums.moneysavingexpert.com/discussion/comment/82146366#Comment_82146366

I read through it, but thought it better to start a new thread with my specific details rather than hijack another individual's thread.

QrizB

Solar appears prohibitively expensive given I can have electric at 6.99 p/kWh with a battery

That's only half the calculation, though. You can sell your solar-generated electricity to EDF for 13p/kWh.

A kilowatt of panels can be put on your roof for about £1000, and in a good location will generate around 1000 kWh a year. That's £130 a year for a £1000 outlay. Or, put another way, 4kW of panels would cost £4k and earn you £520 - a similar cost and return to your battery.

There's no guarantee that EDF will continue to offer off-peak electricity for 7p/kWh for the decade your battery lasts. And there's no guarantee they'll continue offering 13p/kWh for export for the same period. But, by having both, you can have a fair degree of certainty that, whether prices rise or fall, what you lose on the swings you'll get back on the roundabouts.

So the price of installation is key to determine whether it is worth it or not, probably needing a cost under about £4,000 to justify.

You might struggle with that a bit. You're probably looking at £4.5-5k for a professionally-installed 10kW battery with all the paperwork and certifications. Or perhaps £9k including 4-5kWp of solar.

Bigger PV systems tend to cost less, on a pence-per-watt basis. If there's room on your roof for more than 8 panels, bigger is usually better. See for example this recent estimate from @Screwdriva for a Tesla PW3 and 17 panels (almost 9kW of solar) for £12.5k installed.

That would save you your £572 on import and could earn another ~£1100/yr from export.

squirrelpie

Of which 17-hour daytime use: 2,500kWh

Of which 8 hour nighttime use: 3,000 kWh (this is optimised as much as I can)

17+8 = 25 and there are only 24 hours in a day?

hugheskevi

https://forums.moneysavingexpert.com/discussion/comment/82146585#Comment_82146585

Ooops, meant to be 7 hour nighttime use, sorry.

hugheskevi

https://forums.moneysavingexpert.com/discussion/comment/82146380#Comment_82146380

Interesting, and I think this changes the outcome very significantly

I have a big roof, so I could fit a lot of panels. If I were to have a large solar set-up, the case for battery storage weakens a lot.

I could use cheap overnight electric for just over half my use, and in a lot of the year solar would cover most or all of the daytime use. It would just be in winter that I would be using a chunk of expensive daytime mains electric. The benefit from a battery would be small and as we have reliable supply I wouldn't benefit from EPS.

So maybe a big solar set-up without a battery could be the way forward.

Thanks!

Reed_Richards

Five years ago I was paying a flat rate of 12.374p (before VAT) per kWh for all my electricity. Who's to say what the situation and prices will be like in another 5 years?

hugheskevi

https://forums.moneysavingexpert.com/discussion/comment/82146644#Comment_82146644

I agree, everything is very uncertain now. The lifespan of solar is a strong argument in its favour, whereas the likely shorter lifespan of batteries makes everything far more marginal.

There is also the consideration of waiting to benefit from tech develops.

hugheskevi

Just to circle back on this,

I decided to go with quite a big solar installation, an 11kw system that should generate about 9,000 kwh per year. That is paired with a 9kwh battery. The cost advantages of getting everything done at the same time and making it all quite big are in favour of the bigger installation.

The plan will be to charge our electric car and the house battery overnight from mains on a cheap electricity tariff (EDF Go Electric as things currently stand). The battery can then power the house during the day, with a very minimal contribution from solar, with almost all of the generation being exported.

I'm not getting EPS initially, as our power supply is reliable. The battery can be easily expanded should future changes make that desirable.

I don't plan to get a heat pump in the near future as we have a good new boiler installed a couple of years ago, but as and when the boiler next needs replacing, getting a heat pump will be a serious consideration.

QrizB

Thank you for the update!

It would be good to know what specific equipment you're getting; there might be some other forumites who can give you tips on how to get the most out of your battery, for example, or tips on how to configure your inverter.

Don't be put off if the first few months aren't particularly productive. UK solar generation is (unsurprisingly) biased towards the summer months. It'll start to turn around once we get to March.