Solar + battery vs solar only
What could a 25 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£842 estimated annual value
£8,750 illustrative extra battery cost · 4,500 kWh solar shifted · 1,750 kWh tariff shifted
Sensitivity
| Scenario | Solar shifted | Tariff shifted | Import/export | Cheap rate | Annual value | Simple payback |
|---|---|---|---|---|---|---|
| Cautious | 3,150 kWh | 1,225 kWh | 24/15p | 10p | £410/yr | 21.4 yrs |
| Base | 4,500 kWh | 1,750 kWh | 28/15p | 8p | £842/yr | 10.4 yrs |
| High-use | 5,400 kWh | 2,100 kWh | 32/10p | 7p | £1,542/yr | 5.7 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.