RELATED: Is a home battery worth it in the UK?
Size it by your evening and overnight use
A battery covers the hours your panels are not generating and the grid is expensive. That is roughly 4pm to 8am. Most homes use 50% to 70% of their daily electricity in that window.
The method is simple. Take your annual usage from your supplier app and divide by 365 for a daily figure. Then aim to match the battery to the part of that day you use after the sun goes down. If you use 6kWh across the evening and night, a battery around 6kWh to 7kWh usable covers it.
Fitting a battery far bigger than your nightly use just leaves capacity sitting empty. Fitting one too small means you buy peak power once it runs flat. The sweet spot sits between the two.
Usage band guide
Use this as a starting point. We confirm the exact size at survey against your real consumption.
| Yearly usage | Daily use | No EV | With solar | With an EV |
|---|---|---|---|---|
| Low, around 2,700 kWh | 7 to 8 kWh | 3 to 5 kWh | 5 kWh | 5 to 7 kWh |
| Medium, 3,100 to 3,600 kWh | 8 to 10 kWh | 5 to 8 kWh | 8 to 10 kWh | 10 to 13 kWh |
| High, 4,100 kWh or more | 11 to 15 kWh | 10 to 13.5 kWh | 10 to 15 kWh | 13.5 kWh or more |
An EV pushes you up a band, because home charging adds a large evening load. A battery covers the house and clips the peaks of EV charging. It does not replace a dedicated smart tariff for the car itself.
Why survey first sizing matters
Online calculators give a rough band. They cannot see your consumption pattern, your tariff, or whether you export solar at midday. That is why we look at your actual numbers before we quote.
We are not tied to one manufacturer, so we size to your home rather than to whatever unit we happen to sell. If your usage is set to grow, an EV or a heat pump on the way, we build a little headroom in without oversizing to the point the battery rarely fills. Get the size right and the battery pays. Get it wrong and it sits half used.
