Home Backup Battery Size Calculator
Build a critical-load budget before choosing a backup battery.
Suggested nameplate capacity2,720 WhAlso verify continuous and surge inverter output for simultaneous loads.
What this calculator does
It converts your daily critical loads into watt-hours, multiplies by outage duration, then divides by a usable-energy factor to account for reserve and conversion losses.
What it does not do
It does not verify motor-starting surge, 120/240V requirements, transfer-switch compatibility or code-compliant installation. Those are separate constraints.