PV and battery system justify

Engeroosi

Having an internal argument with myself and wondering if it's just me overthinking it as per usual.

These are hypothetical values with some data driven guesstimates.

16 x Solar panels with 10kwh battery storage. Will save me ~£500 per year

In 2022 was quoted roughly £14,500.
In 2025 was quoted roughly £11,500.

So, for a newer, more efficient and latest tech it's £3k less over 3 years. 

By not installing back in 2022 I could have saved myself £3k and got the better system installed now. 

That £3k is also double the amount it would have saved me in electric over the last 3 years. 

Obviously the system costs can't keep dropping, but the evidence in the market is that it is currently still plummeting (more So battery costs)

Am I being daft here or is the above scenario actually the case? 

Niv

More to the point. Do you need a battery / do you need a battery now? I installed without a battery and my annual electricity bill is £0 (I pay £20 pm for standing charge). Selling back to the grid covers the cost of everything I take from the grid.

ComicGeek

I wouldn't say there has been a significant improvement in the technology over those 3 years. Gradual minor improvements happen all the time, there's always something (slightly/significantly) better around the corner.

Payback on £11,500 capital cost with a £500/yr saving is still pretty poor. High battery prices are still making larger combined systems poor value, and that's even with the solar panels normally around 7/8 yr payback. £500/yr saving is pretty low though, so I would question whether that's correct - it's also a fairly large solar panel and battery size if it's a normal house without large summer electricity needs (ie EV charging, swimming pool, air con etc), so again you're paying for more than you can use anyway.

IMO there's still only a benefit for battery storage in particular scenarios:
1) Where you can use cheap overnight electricity to charge up the battery in winter.
2) Where you want to use the battery to provide power to the house during power cuts - but would need the battery charged ready for a power cut, sod's law is that it's empty when you need it.

In all other situations you're unlikely to ever get your money back on the capital cost of the battery.

Engeroosi

I have an EV.

I'm on a tariff with cheap overnight rate and smart charging during day which I rarely use. (My ev has free charging so tend to use charging at home only for longer journeys)

Annual usage is 4500 roughly.

Going to install induction hob soon so usage may go up. Also have an immersion heater which could also use.(currently use calor gas for it)

Battery only will be ~£4000. Its the solar etc that bumps price up. My guess is due to cost of scaffolding etc. 

Grenage

Batteries are tough to justify in most situations, it rarely pays for itself.

The primary cost is labour.  I have 3.4kw of panels and the material cost was £1,100 for the panels, inverter, and mounts.

Engeroosi

Got quote for little less than £10k. 14 panels, inverter, Eddi diverter and 10kwh battery. 

Would require a loan to pay for it, so can add interest on over 5 years. 

100% getting cheaper faster than any potential savings. 

~£500 year savings. 
~£1000 cheaper for system cost every year that passes. 

Surely makes more sense to hold off another year until the prices of system stop falling and evens out with the savings each year. (Which will go up and energy costs rise) 

jonnydeppiwish!

Get as many panels as you can fit (8-9kwh array) with a G99, at least a 9.5kw battery, car charger and immersion heater for around 10k. I have this by 15kw battery and an EV. 180miles is £2.40, and I’ve spent 
-£68 on gas and Electric in March

Niv

Engeroosi said:

Got quote for little less than £10k. 14 panels, inverter, Eddi diverter and 10kwh battery. 

Would require a loan to pay for it, so can add interest on over 5 years. 

100% getting cheaper faster than any potential savings. 

~£500 year savings. 
~£1000 cheaper for system cost every year that passes. 

Surely makes more sense to hold off another year until the prices of system stop falling and evens out with the savings each year. (Which will go up and energy costs rise) 

I believe your savings calculations are incomplete. You may save £500 from using at point of generation but I think you have not calculated income from selling excess to the grid. I have a similar sized system to your proposed system and it covers all my electricity costs. 

2024 for comparison
Production: 5.21MWh
Consumption: 4.02MWh
Self consumption: 2.27MWh
Exported to grid: 2.95MWh

I would be shocked if you only knock £500 off with that sized system.

tripled

I have 12 panels (3.68kW inverter) and last year my export alone was just under £500.

I also estimate I've saved a similar amount again through daytime use of the solar and the 5kWh battery charged overnight at a cheaper rate.

Total savings are around £1k p/a.

My import bill for last year - including the standing charge - added up to £750ish, with £500 export that meant I only paid £250 for electricity - most of that being standing charge. And that's running two EVs.

There's something not quite right if your system, with a battery twice the size, is only saving you £500 p/a.

Engeroosi

I wouldn't plan to export any, whatever I generate will be used or stored to be used when I'm not generating. Ie overnight or poor weather days. Living in Scotland there are alot of long grey days. 

Alnat1

You definitely WILL export and you may as well get 15-16.5p for each kWh you send back to the grid. Huge amounts of storage don't always make sense when calculating ROI but a small battery can help for overnight use. Find a site that does PVGIS calculations and you can find out how much a potential PV system might generate each month on your roof, in your location.

The credit you make on your export in summer is what pays/goes towards your winter bills. Our not so big 5.25 kWp of panels has already generated 30kWh on several days this month in the north of England. Yes, we put some in the battery to cover overnight use but already this month 221kWh has gone back to the grid, that's £33 credit.

If you do decide on a battery there are Time of Use tariffs that can help you save. The battery can be filled at cheaper times and used when it's more expensive from the grid. We have a heat pump and a tariff with 3 cheaper periods each day. We fill the battery (and run the house load - also think washer, dryer, dishwasher etc) when it's 14p/kWh and then draw from the battery during the expensive slots.

Putting it simply, we haven't paid an energy bill since 2022 - but we did invest £12.5K in PV/battery/ASHP.