Work out how long a solar battery will run essential loads during an outage.
Backup duration depends on the reduced essential load rather than normal consumption. With solar recharging during the day, a modest battery can sustain essentials indefinitely. Whole-home backup needs several times the battery of essential-circuit backup, which is why critical-load panels are standard practice.
Solar Battery Backup
Backup hours = usable kWh × 1,000 ÷ load in watts
Backup hours = usable kWh × 1,000 ÷ load in watts Backup duration depends on the reduced essential load rather than normal consumption. With solar recharging during the day, a modest battery can sustain essentials indefinitely.
Whole-home backup needs several times the battery of essential-circuit backup, which is why critical-load panels are standard practice.
This calculator takes 5 inputs: Battery capacity, Usable depth of discharge, Essential load, Inverter efficiency, Solar input during the outage. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.