Most people assume a home battery only makes sense alongside solar panels. That was true when the only job of a battery was storing surplus generation. It is no longer true, because time-of-use tariffs have changed the economics completely.
The arbitrage case
On a smart tariff you can import at a low overnight rate and discharge through the expensive evening peak. Across a year, a 10 kWh battery cycled most days on a good tariff typically shifts £500–£800 of consumption from peak to off-peak rates. No panels required.
Sizing it properly
- Look at your evening consumption between 4pm and 9pm — that is what the battery has to cover
- Most three to four bed homes are well served by 8–13 kWh of usable capacity
- Inverter power output matters as much as capacity if you want to run an oven and a kettle from stored energy
- Oversizing is the most common mistake — a battery you never fully cycle earns nothing
Where it does not stack up
If you are on a flat-rate tariff and unwilling to switch, or your evening usage is very small, the numbers get thin. We will tell you that at survey rather than sell you a box that sits idle.
Add solar to the same battery later and the case improves again — you are then storing free generation as well as cheap import.
