Battery backup math is deceptively simple
Every battery spec sheet quotes an Ah rating at nominal voltage — but the usable energy is much less. After factoring in depth of discharge, inverter efficiency, and cable losses, a 150 Ah lithium battery at 48V delivers about 5.8 kWh (not 7.2 kWh). Our calculator runs this math correctly for you, including reference scenarios like “fridge + fan + lights” and “1.5 Ton AC alone.”
If the backup hours look short, size up the battery with our Battery Size Calculator, or measure and trim your real load using the Appliance Load Calculator.