Battery Runtime Calculator

How It Works

Battery runtime depends on total energy capacity, recommended depth of discharge (DoD), and conversion inefficiencies:

1. Nominal Energy (Wh): If capacity is supplied in Amp-hours (Ah), energy equals Ah × V. When supplied directly in Watt-hours (Wh), that rating is used directly.
2. Usable Energy (Wh): To prevent premature cell degradation, different chemistries allow different safe discharge percentages:

• Lead-Acid / AGM: 50% DoD
• Lithium NMC / Li-ion: 80% DoD
• Lithium Iron Phosphate (LiFePO4): 90% DoD

3. Inverter & Cabling Loss: Converting DC battery power to AC wall power involves thermal and conversion loss, commonly operating between 80% and 92% efficiency.

Usable Wh = Nominal Wh × DoD × (Inverter Efficiency%) ÷ (100)

Runtime (hours) = (Usable Wh) ÷ (Continuous Load (W))

Assumptions: Continuous, non-surging load. Peukert's effect on lead-acid batteries at very high discharge rates is not modeled; results represent standard C/10 to C/20 discharge rates.