Space Heater vs Central Heat Cost for One Room

A 1,500-watt heater costs the electricity rate times 1.5 kWh per hour, and all electric resistance heaters are 100-percent efficient to run.

Most portable heaters for a single room are electric resistance designs: they use a heating element to convert 100 percent of the power supplied to heat. At 1,500 watts, that's 1.5 kilowatt-hours per hour in basic arithmetic. In energy terms, that 1,500 watts stays in the conditioned space, after accounting for heat loss in the connecting ductwork.

That cost-to-run figure holds across ceramic, fan, underfloor, and all other varieties of electric resistor. The heat flapping from a fan-forced heater is electrically cheaper than keeping warm with a quiet but large oil-filled column: they cost the same to run if their wattage matches. Even the supposedly energy-efficient infrared heaters subject the power meter to the same same ductless resistance.

All resistive heaters in the heating area — convert that input wattage one for one to heat, U.S. Department of Energy test procedures say. The EECA rules for electric heaters in Oceania specify a 100 percent efficiency point of use. For example, a 1,500-watt heater at 20¢ per kWh costs $0.30 an hour to run, even before the fan or infrared or radiant warm air from a focal emitter.

What central heat changes

While the rate card determines how much it will cost to run a given 1,500-watt heater, the operating cost of running one heater compared to central heating changes every time the delivered cost of the central heat changes.

The U.S. average national electric rate is 18.44¢ per kilowatt-hour for June 2026. But in the state of Idaho, the average rate is 12.35¢. In Hawaii, that delivered cost is 52¢. (See: HeatingCostCalculator.com, Heater Cost Per Hour (2026).)

In a separately metered room, the delivered cost is the electricity rate period. But in an attached home for the entire house connected to a furnace or a boiler and ductwork or a fireplace by the local climate, the delivered cost varies. Precisely because there's more ancillary heat loss, the exact cost varies.

For many homeowners with central heat, the easiest answer to comparing one versus the other is not to compare one versus the other. The delivered cost of central heat may vary, but in a temperature-controlled room such as a bedroom or a den, that delivered cost remains zero if that system doesn't heat that space.

When one-room heating is cheaper

The major rule of thumb: resistive space heaters often win on cost in a small living area with the rest of the house at a setback or off.

Space heaters offer room-by-room control: for example, in a south-facing home, heating one bedroom and setting the rest of the house to 58°F is the zone-heating logic. Electrical space heaters may not grow heat that cheap, but with a smaller area to warm, the lower BTUs come cheaper than heating the whole house to a comfortable 72°F.

Running more than one space heater is still efficient, but the circuit limit may kick in. Depends on the specific wiring for a particular home, but..

Safety and wiring rules

A heated coil or metal surface present safety concerns. Always turn the space heater off before leaving a room or going to sleep, as the number-one safety concern is unattended operation.

Space heaters draw their own circuit, and must be plugged directly into a wall outlet, not into an extension cord or strip. That's the principle behind the direct-wall-outlet rule even in a well-lit bedroom.

And the heater should have a listed safety certification, such as a UL or MEL label.

Why space heaters may run longer

Another rule: room heaters don't turn the space warm and shut off, but continue to make power until an automatic thermostat command to turn off or a timer switch commands it.

The steady heat from a heater doesn't turn that zone warm and off compared to a sudden burst from a central furnace, and the steady power draw warms the small room before the heater turns off. People don't notice one fan may run longer than another, and simply find that a portable sometimes stays on longer than expected.

If the space is not well-sealed, heat escapes. And people tend to run space heaters longer than needed on a brutal winter evening. in general, for both wear and tear, usage and wear patterns