Power station runtime formula
Multiply rated battery capacity in watt-hours by usable efficiency, then divide by the total running load in watts. The result is an estimate in hours: battery Wh × efficiency ÷ load W.
We default to 85% efficiency because an AC inverter, internal electronics, temperature, and battery protection consume part of the advertised capacity. Low-voltage DC or USB loads can behave differently, so use the output type you actually plan to use.
Example: A 1,024Wh station at 85% efficiency provides about 870 usable Wh. At a steady 150W load, estimated runtime is 5.8 hours.
Common appliance planning ranges
- Refrigerator: often cycles rather than drawing continuously; measure 24-hour energy use whenever possible.
- CPAP: humidifier and heated-tube settings can materially increase consumption.
- Internet and charging: usually modest loads, but leaving the AC inverter on adds overhead.
- Electric heat and cooking: high-wattage resistance loads can empty a portable battery surprisingly quickly.
Why the estimate can differ from real runtime
Startup surges, compressor cycling, cold weather, battery age, inverter idle draw, and manufacturer reserve limits all affect the result. Treat the calculator as a sizing estimate, then test the exact appliance and power station before an outage.