November 3, 2026 · By Diego Gómez

Space heater keeps tripping the breaker? Why it happens and how to fix it

A 1500-watt space heater draws about 12.5 amps, close to the limit of a standard 15-amp circuit. Why breakers trip, what to do about it, and when to call an electrician.

You plug in the space heater, switch it to high, and a few minutes later half the room goes dark. It's one of the most common winter complaints, and usually it's simple math rather than a faulty heater.

The math

Almost every plug-in heater sold in the US tops out at 1500 watts. On a 120-volt outlet that's about 12.5 amps. Most bedroom and living room outlets are on a 15-amp circuit, and electricians generally size continuous loads (anything running three hours or more) at no more than 80% of the breaker rating, which is 12 amps. So a heater on high already uses the whole circuit before you add a TV, a lamp or a vacuum.

What to do

1. Find out what else is on that circuit. Rooms often share a breaker; a hair dryer or vacuum in the next room can be the last straw.
2. Use the low setting. Many heaters have a 750–900 W setting that draws roughly 6–7.5 amps and leaves room for other things.
3. Move the heater to an outlet on a less loaded circuit.
4. Plug it straight into the wall. Most heater manuals say not to use an extension cord or power strip; they can overheat at these loads. See our space heater safety guide and the CPSC's space heater tips.
5. Let the thermostat do the work. A heater with a real thermostat drops to low or cycles off once the room is warm.

Warning signs: call an electrician

• The plug, outlet or wall plate feels hot, looks discolored or smells of burning plastic.
• The breaker trips even when the heater is the only thing running.
• Lights flicker or dim badly every time the heater kicks on.

Those point to a worn outlet or a wiring problem, not just an overloaded circuit.

Heaters that are easier on your circuits

For small rooms, a heater with a 900 W setting is often enough, and oil-filled radiators with 600/900/1500 W settings let you pick a lower load. Every 1500 W heater costs the same to run: about 27.0¢ an hour at the 18¢/kWh US average. Compare models in space heaters.

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