Solar Battery Storage Sizing Calculator
Find the right battery size for your solar installation based on your daily energy usage.
kWh/day
Annual kWh ÷ 365. UK 3-bed home ≈ 8–12 kWh/day.
kWh/day
%
Lithium batteries: 80–90%. Lower = longer battery life.
days
Days of backup without solar. 1 = overnight only.
kWh
kWh
Battery Recommendation
Formulas
- Total daily load = Usage + EV + Heat Pump
- Storage needed = Total load × Autonomy days
- Usable kWh needed = Storage needed − Solar self-used
- Battery capacity = Usable kWh needed / DoD
- Recommended = Battery capacity × 1.2 (safety margin)