Continuous load
245 W
Backup energy calculator
Choose essential loads and their operating hours. Energy and starting demand are checked separately.
System assumptions
Results update automatically
Estimated load surge
545 W
Load energy
1.2 kWh
Battery — required usable energy
1.3 kWh
Battery — nominal energy
1.64 kWh
Inverter — continuous output
400 W
Inverter — surge output
600 W
How this is calculated
We sum power × quantity × each appliance’s operating hours, capped at the backup duration. Usable battery energy accounts for inverter losses; nominal energy also includes discharge reserve. Inverter continuous output includes 25% margin and surge 10%.
Continuous load assumes enabled appliances run together; surge adds simultaneous starts, a conservative scenario. Refrigerator hours mean actual compressor operating time. Use measurements and manufacturer data.
Final selection and installation must be checked by a qualified electrician against manufacturer instructions and applicable electrical requirements. Never backfeed house wiring through a socket with a generator or inverter.