kWh/day
%
Nominal battery capacity13.5 kWh
Capacity after planning reserve12.2 kWh
Estimated backup duration19.4 hours
Published continuous power per unit11.5 kW
Backup duration is an energy-only planning estimate. It does not verify whether the battery can start or run every selected appliance at the same time. HVAC, pumps and motors can require high surge power, and solar production during an outage can extend runtime.
Outage runtime
Need hours instead of daily backup-energy sizing?
Use the dedicated runtime calculator when you know the average critical load in kW. It separates backup reserve from full usable battery capacity and shows how runtime changes across several load levels.
Battery sizing guide
Not sure how many battery units to start with?
Compare 5-30 kWh/day backup scenarios using current Tesla Powerwall 3, Enphase IQ Battery 5P and FranklinWH aPower 2 usable-capacity specifications.
How to get a useful result
- Use the kWh consumed by the loads you actually want to keep running during an outage, not necessarily your whole home's normal daily usage.
- Keep a reserve if you do not want the planning model to assume every published kWh is available for backup.
- Check continuous and surge power separately. Energy capacity alone cannot tell you whether a battery can start a large air conditioner or pump.
- Solar production during daylight can extend backup duration, but this first version does not credit outage-time solar generation.