When a winter storm takes out the power, the first question many people ask is whether their battery backup can run a space heater. The short answer: sometimes, but only briefly. Electric heaters are among the most power-hungry appliances in a home, and they drain portable batteries far faster than almost anything else.
Why space heaters are so demanding
Most plug-in electric space heaters draw about 1,500 watts on high and roughly 750 watts on low. For comparison, a refrigerator averages well under 100 watts over a day, and a CPAP often uses less than 60 watts. Turning electricity directly into heat simply takes a lot of energy.
That creates two problems:
- Output: the power station's continuous AC rating must exceed the heater's draw. Many smaller units cannot run a 1,500 W heater at all.
- Capacity: even when a unit can run the heater, the battery empties quickly.
How long will it last?
Runtime in hours = usable Wh ÷ heater watts, using about 85% of rated capacity as usable energy.
| Battery capacity | Heater on low (~750 W) | Heater on high (~1,500 W) |
|---|---|---|
| 1,000 Wh | ~1 hour 10 min | ~35 min |
| 2,000 Wh | ~2 hours 15 min | ~1 hour 10 min |
| 3,000 Wh | ~3 hours 25 min | ~1 hour 40 min |
Estimates assume continuous operation with no other loads. A heater with a thermostat that cycles on and off will run somewhat longer. These are planning figures, not test results.
In other words, a typical home backup battery could keep a small room warm for an hour or two, not through the night. That battery energy is usually better spent on the refrigerator, medical devices, lights, and communication.
Better ways to stay warm on battery power
- Electric blankets and heated mattress pads warm your body directly and typically use a small fraction of a space heater's wattage. Check the label for your model's rating.
- Heat one room. Close doors, cover windows with blankets or curtains, and gather in the smallest room you can.
- Dress in layers, including hats and socks, and use sleeping bags rated for cold weather.
- Run a furnace blower, if safe. Some gas furnaces need only a modest amount of electricity for their controls and blower. This usually requires a proper transfer switch or inlet installed by a licensed electrician. See our guide to connecting backup power to your home.
Safety: what never to do
- Never use a gas stove, oven, grill, or camp heater to heat your home unless it is specifically designed and approved for indoor use. These can produce deadly carbon monoxide.
- Install battery-powered carbon monoxide alarms and test them before winter.
- Keep space heaters at least 3 feet from anything that can burn, and never leave them running unattended.
- Plug heaters directly into the power station's AC outlet, not into a power strip or light-duty extension cord.
The bottom line
A portable power station can run a space heater only for a short time, and only if its continuous output is high enough. For winter outages, plan to stay warm with layers and low-wattage heated bedding, and save battery energy for essentials. Use our backup power calculator to see how a heater compares with your other needs, and read how much solar panels produce in winter.
This guide is general information, not electrical or medical advice. Follow manufacturer instructions, and use a licensed electrician for any connection to your home's wiring.