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How We Calculate
Assumptions
- Inverter efficiency 85%: typical for DC→AC conversion in portable power stations (manufacturers measure 85–92% at ideal loads).
- Solar derating 75%: real-world output of panels vs. rated watts (temperature, angle, soiling, MPPT losses).
- Duty cycle: fridges and freezers use their average draw (e.g. 55 W for a full-size fridge ≈ 1.3 kWh/day), not their running watts.
- Peak load: all running watts + the largest single start-up surge (motors rarely start at the exact same moment).
- Generator margin: +20% on running watts for safety and fuel efficiency.
- Battery depth of discharge: 90% for LiFePO4, 50% for AGM/lead-acid.
- Sun hours: rounded annual averages per US state based on NREL solar resource data.
Formulas
Runtime = Wh × 0.85 ÷ average W
Capacity = daily Wh × days ÷ 0.85
Generator = max(running × 1.2, running + largest surge extra)
Solar recharge = Wh ÷ (panel W × 0.75)
Battery Ah = daily Wh × days ÷ DoD ÷ volts
Capacity = daily Wh × days ÷ 0.85
Generator = max(running × 1.2, running + largest surge extra)
Solar recharge = Wh ÷ (panel W × 0.75)
Battery Ah = daily Wh × days ÷ DoD ÷ volts
Product data
Specs come from the manufacturers' published data sheets and are reviewed regularly (last review: 2026-11-02). We don't show prices because they change daily; the price buttons link to current offers.
Results are estimates for planning purposes and don't replace advice from a licensed electrician.