How We Calculate Power Station Runtime

Every page on this site comes from the same transparent formula. The station specs and appliance data live in plain JSON files; nothing is hand-tuned per page.

1. Usable energy

A power station never delivers its full rated capacity. The inverter that creates AC power and the battery management system both lose energy as heat. We assume:

2. Average draw

Appliances with compressors or thermostats (fridges, freezers, AC units, heaters on a thermostat) cycle on and off. We multiply running watts by a typical duty cycle to get average draw. For example, a 180W fridge running a third of the time averages 60W.

3. Runtime

Runtime (hours) = Capacity (Wh) × efficiency ÷ average watts

For battery devices (phones, laptops, e-bikes) we divide usable energy by the device battery size × 1.15 to account for charging losses.

4. Will it start?

We check two limits. Running watts must stay under the station’s continuous AC output, and startup watts must stay under its surge rating. Motors and compressors briefly draw 2–3× their running watts when starting, and that surge is the most common reason a station shuts off. Where a manufacturer doesn’t publish a surge rating, we use the continuous rating.

5. Solar

Solar panels rarely produce their full rating. We assume 75% of rated output and 5 peak-sun hours per day.

Limitations

Real results vary with temperature, battery age, appliance model and settings. Measure your appliance with a plug-in watt meter for the most accurate numbers, then enter them in the calculator.

Data sources

Station capacity, output, surge and solar input come from manufacturer and retailer specification sheets. Each station page links to the source we used. Where regions differ, we use the US (120V) model. Appliance figures are typical values from product labels and published energy data; your own appliance may differ, so check its label.

Data last reviewed 2026-10-17. Spotted an error? Let us know and we’ll fix it.