Device wattage guides
How Many Watts Does a Space Heater Use?
Most plug-in electric space heaters are simple resistance heaters, so they use a lot of power for the heat they provide. They are usually one of the hardest household loads to support from batteries.
Typical wattage ranges
| Load | Watts | Planning note |
|---|---|---|
| Low setting | 600-900 W | Some heaters provide lower settings, but the draw is still significant. |
| High setting | 1,500 W | A standard 120 V portable heater commonly tops out around 1,500 W. |
| Thermostat cycling | 0 or full setting | Many heaters cycle the element on and off rather than using a continuously variable draw. |
Runtime example
With a 2000 Wh battery, a 1500 W load, 85% efficiency, and a 20% reserve, the planning estimate is about about 0.9 hours.
Electric resistance heat drains batteries quickly, so runtime can be short even with a large power station.
Planning tips
- Prioritize insulation, layered clothing, and heating a small occupied room before adding electric heat load.
- Check circuit limits before running multiple heaters.
- For generators, account for the heater plus essential loads running at the same time.
- Use lower settings when possible to stretch runtime and reduce circuit load.
Safety and limits
- Keep space heaters away from bedding, curtains, furniture, and other combustibles.
- Do not use extension cords unless the heater manufacturer allows it and the cord is properly rated.
- Never use outdoor combustion heaters indoors unless they are specifically listed for indoor use.
FAQ
Why do most space heaters use 1,500 watts?
That is near the practical limit for many standard 120 V household circuits and plug-in heaters.
Can a battery run a space heater overnight?
Usually not with typical portable power stations. A 1,500 W heater can drain even a large battery quickly.
Is the low setting much better?
It helps, but 600 to 900 watts is still a large continuous load for backup power.
Related calculators
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