A UK home battery is financially promising when degraded bill savings recover the final installed price comfortably within the warranty—not merely at some point in the distant future.
Use the tariff spread, not the import price alone
If electricity costs 28p/kWh to import and exported solar earns 15p/kWh, the gross opportunity is not 28p. It begins at 13p before battery losses.
Time-of-use tariffs can create additional value, but only where charge windows, export rules and battery controls genuinely support the strategy. Keep that upside separate from the conservative base case.
Apply losses and degradation
Round-trip efficiency means less energy leaves the battery than entered it. Capacity also declines over time. Battery Quote X-Ray defaults to 90% efficiency and reduces output by 2% each year, both shown as assumptions.
- Limit charging to daily solar surplus
- Limit discharge to evening demand
- Subtract lost export income
- Accumulate degraded annual savings
- Compare recovery with the warranty
Treat backup value separately
Backup capability can be valuable, but it is not a bill saving. Decide what resilience is worth to your household instead of hiding it inside a financial return claim.