Watts vs. watt-hours explained
Power station specs use two units that are easy to mix up. Watts (W) measure how fast a device uses power, like speed. Watt-hours (Wh) measure how much energy a battery holds, like the size of a fuel tank.
The formulas
- Energy used = watts × hours. A 60 W laptop running for 5 hours uses 300 Wh.
- Runtime = battery Wh ÷ watts. A 1,000 Wh battery running a 100 W device lasts about 10 hours in theory.
- Real runtime = battery Wh × 0.87 ÷ watts. The 0.87 is inverter efficiency, so the same example gives about 8.7 hours.
Why you don’t get the full number on the box
A power station stores energy as DC and converts it to AC for wall-style outlets. Some energy is lost as heat in that conversion, usually 10–15%. Using USB or DC ports avoids much of that loss.
Other units you’ll see
| Unit | Meaning | Example |
|---|---|---|
| kWh | 1,000 Wh | A 2 kWh battery is 2,000 Wh |
| Amp-hours (Ah) | Charge capacity. Multiply by volts to get Wh | 100 Ah × 12.8 V = 1,280 Wh |
| Inverter rating (W) | The most power the unit can deliver at once | A 1,000 W inverter can’t run a 1,500 W heater |
Remember that watts decide whether a device can run at all, while watt-hours decide how long it keeps running.