Hours = Ah × V × usable % × efficiency ÷ load watts. Example: 100 Ah × 12.8 V × 0.9 × 0.9 ÷ 100 W ≈ 10.4 hours. Loads that cycle on and off (fridges, furnaces) should use their average watts, not the nameplate.
| Load | Approx. runtime |
|---|---|
| 50 W | 20.7 h |
| 100 W | 10.4 h |
| 200 W | 5.2 h |
| 500 W | 2.1 h |
| 1000 W | 1.0 h |
Safety: These are general estimates, not a design. Follow your equipment manufacturer's instructions and local electrical code, and consult a qualified electrician for anything connected to shore power, a house, or high-current batteries.
A 12 V 100 Ah lithium battery stores about 1,280 Wh. At 100 W through an inverter that is roughly 10 hours; at 1,000 W about 1 hour. An AGM battery of the same rating gives about half that if you stop at 50%.
About 1 hour for LiFePO4 (1,280 Wh × 0.9 usable × 0.9 inverter ≈ 1,040 Wh). Check that the battery BMS allows ~95 A continuous.
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