A battery rated in amp-hours does not translate directly into hours of runtime. Depth of discharge and inverter losses both take a share before an appliance sees any power. These pages work out real runtime, appliance by appliance and battery by battery.
A 12V 100Ah LiFePO4 battery at 80 percent depth of discharge through a 90 percent efficient inverter delivers about 864 usable watt-hours, not the 1,200 the nameplate suggests. That gap is the whole reason these pages exist.