Battery-only needs the right tariff
Without solar, the financial case usually depends on charging cheaply off-peak and discharging during expensive periods. The wider the tariff spread and the more consistently the battery cycles, the stronger the case becomes.
| Tariff pattern | Battery case |
|---|---|
| Small off-peak spread | Usually weak because savings per cycle are limited. |
| Wide off-peak spread | Can work if the household cycles the battery most days. |
| Solar plus time-of-use | Often stronger because stored solar and cheap imports can both contribute. |
Solar plus battery is a different calculation
With solar, the battery captures more daytime generation for evening use. That increases self-consumption but may reduce export income, so the model compares both effects.