A full example
A 12 kWh night load, with a lithium battery at 90% depth of discharge and 93% efficiency:
| Capacity: 12 ÷ (0.90 × 0.93) | 14.3 kWh |
| Life margin to stay sufficient at 80%: 14.3 ÷ 0.80 | 17.9 kWh |
These are typical estimating values, replaced by the exact model's datasheet in the final design.
What also matters
- Discharge rate: a large peak load can exceed the battery's power even when its energy is enough.
- Temperature: heat shortens life, so choose a shaded place within datasheet limits.
- Compatibility: the battery management system must communicate with the inverter.