Home battery capacity follows the energy required by selected loads during an outage. Inverter power must be checked separately.
Load profile
List critical appliances with measured power and operating time. For cycling equipment, use daily consumption rather than multiplying nameplate maximum power by 24 hours.
Reproducible example
Assumed loads need 4 kWh at the output. With example efficiency 0.90 and usable battery fraction 0.80, nominal energy is 4/(0.90×0.80) = 5.56 kWh before additional margins.
Battery limits
Check discharge limits, BMS, currents, charge and discharge temperatures and ageing against product documentation. The example factors are not specifications for an arbitrary battery.
Restoring charge
The battery must recharge within the available time and power. Winter PV is not guaranteed; review grid charging, any generator backup and source-transfer rules.
Common mistakes and safety
Nominal kWh are not usable kWh, and sufficient energy does not guarantee pump starting. Installation location, protection and compatibility require design; the calculator provides only a scenario estimate.
| Item | Parameter | Check / result |
|---|---|---|
| Loads | 4 kWh | Assumed demand |
| Factors | 0.90 × 0.80 | Assumptions |
| Nominal | 5.56 kWh | Before margins |
What this means for your project
Enter measured data into the calculator scenario. Before procurement, check starting currents, temperature limits, BMS compatibility and recharge capability.
Sources and scope of review
Related reading
- Mechanical Ventilation with Heat Recovery: How It Works
- Heat Pumps in Low-Energy Homes
- Critical Loads: Where to Start with Backup Power