Solar + battery vs solar only
What could a 20 kWh battery add to solar?
The model separates the value of extra solar self-use from optional tariff shifting. That avoids treating exported solar as if it had no value.
Illustrative base case£673 estimated annual value
£7,500 illustrative extra battery cost · 3,600 kWh solar shifted · 1,400 kWh tariff shifted
Sensitivity
| Scenario | Solar shifted | Tariff shifted | Import/export | Cheap rate | Annual value | Simple payback |
|---|---|---|---|---|---|---|
| Cautious | 2,520 kWh | 980 kWh | 24/15p | 10p | £328/yr | 22.9 yrs |
| Base | 3,600 kWh | 1,400 kWh | 28/15p | 8p | £673/yr | 11.1 yrs |
| High-use | 4,320 kWh | 1,680 kWh | 32/10p | 7p | £1,233/yr | 6.1 yrs |
This is a planning comparison, not a recommendation for a particular battery size. Actual half-hourly load, battery power, usable capacity, export tariff and degradation can change the result materially.