Watt-hours vs. watts: two different checks before buying a battery
Understand battery capacity, output power and why both matter when choosing a portable power station.
Open the calculator with a relevant appliance selection. Adjust it to your needs.
Build my backup plan →Watts describe the rate of energy use
A constant 100 W load consumes 100 Wh in one hour. Run it for five hours and it consumes 500 Wh. Two identical loads running together use energy twice as fast.
An appliance’s adapter rating is often a maximum, not its average consumption. A device that charges intermittently may use less energy than its maximum rating suggests.
Watt-hours describe stored or consumed energy
In an ideal example with no losses or reserve, a 1,000 Wh battery supplies a constant 100 W load for ten hours. Real batteries lose energy during conversion, and an active inverter consumes energy even under a light load.
Our calculator applies conversion efficiency, idle consumption, starting charge, reserve and battery health separately. You can inspect and change each assumption.
A larger battery is not automatically a stronger inverter
Capacity and output power are separate specifications. A battery with plenty of Wh can still have an output limit below the watts your appliances need simultaneously.
Motors introduce another requirement: starting power and its duration. Our capacity comparison leaves this check open when the relevant specifications are missing.
Sources and method
Reviewed September 14, 2026. Examples illustrate the calculation; they are not appliance tests.