Case study · Surrey
Modelled · install underwayA new all-electric home, doing everything right, still paying £6,200 a year.
One obvious fix would have made the bill worse. The fix that worked had nothing to do with more solar. Here is the whole story in four numbers, then how we got there.
Bill now / yr
Modelled saving / yr
Off the bill
Year payback
A modelled, pre-install projection for this specific home, on its own load and tariff. Your home's numbers will be different.
What the battery does to the bill
More than half the annual bill, gone.
A modelled £3,213-a-year saving on the household's own load. Pre-install projection; year-one metered figures will follow once the system is live.
The setup
Going all-electric was right. It just concentrated the whole bill on one expensive habit.
A brand new home, no gas.
Built 2024 to a high spec. Three air-source heat pumps (one for the pool), two e-boilers, an EV and a plug-in hybrid.
£6,200 a year, on Cosy.
Structural, not a mistake. Going fully electric puts the entire household on one volatile commodity.
The instinct: more solar.
A bigger array, more generation. But daytime solar can’t cover heat-pump-plus-pool winter load. The lever is elsewhere.
The instinct was more solar. The model found the lever somewhere else entirely.
What we modelled
One obvious move loses money. The other pays back in 4.5 years.
| Configuration | Tariff switch onlyCosy → Intelligent Octopus Go | Recommended · chosen install3× Battery modulesOn IGo · as procured |
|---|---|---|
| Battery | 0 kWh | 40.5 kWh |
| Install cost | £0 | ~£14,000 |
| Annual saving | −£1,000~16% more than today | £3,21352% of current bill |
| Payback | N/A | 4.5 yrs |
Where the saving comes from
The arbitrage
The battery isn't there to store solar. It's there to buy power at the right time of day.
The 10-year view
~£18,000 net by year 10, and that's the cautious read.
Payback
0.0years
Warranty
0years
Net, to year 10
£0
Why these numbers hold
Their data, not an average.
Modelled on this household’s own load profile, not a postcode estimate or a synthetic year.
Real, published tariffs.
Run against Octopus’s published 2026 tariffs, Cosy and Intelligent Octopus Go, not illustrative rates.
No stake in the answer.
We sell no hardware and take no installer commission. Nothing in our fee depends on what the model returns.
The fine print: sizing, tariff mechanics and the 10-year caveat
Switching from Cosy to Intelligent Octopus Go on its own costs this household roughly £1,000 a year more. Without a battery, IGo's higher peak rate outweighs the cheap overnight window for this load profile.
A single 13.5 kWh module does not pay back here. Three modules (40.5 kWh) are sized to the household's actual overnight-shiftable load, not to generation capacity.
The 10-year figure is where the warranty ends, not the battery. Systems of this class commonly run 12 to 20 years; any saving past year 10 is unmodelled upside.
Savings are a pre-install projection, undiscounted and indicative; year-one metered figures follow once the system is live.
The takeaway
“New build, all-electric, £6,000-a-year bill. The fix wasn't solar. It was buying electricity at the right time of day.”
New Energy Education modelling for a five-bed 2024 new-build, Surrey
Talk to us
Curious what the numbers look like for your home?
This was modelled for one specific home. Yours has its own load, tariff and roof, so the answer will be different. We work it out from your own data.