An electric space heater saves only if the rest of the house gets colder

Run a plug-in heater only while the central thermostat is turned down for the rest of the house, and only if that setback saves more than the heater costs. A common rating is 1,500 watts: 22 of the 27 models CPSC staff bought for its February 2023 assessment of portable electric heaters had that maximum. At full power that is 1.5 kWh an hour, about 27 cents at the US average residential price of 18.31 cents per kWh in July 2026 (preliminary), from EIA's Electric Power Monthly, Table 5.6.A. If the central thermostat stays where it was, those kWh land on top of the heating bill. Renters and owners can both do this, and it is free with a heater you already own.

A 1,500-watt heater uses 9 kWh in six hours

The heater's label gives its maximum draw in watts. Price it the way you price any appliance: watts × hours ÷ 1,000 gives kWh, and kWh × your price per kWh gives dollars. Your price is the electric bill's dollars divided by its kWh, or your state's row in EIA Table 5.6.A.

Example, with published figures and one assumption. A heater rated 1,500 watts, the maximum on 22 of the 27 heaters in CPSC's 2023 assessment, runs on high for 6 hours a day; the 6 hours are the example's own assumption. 1,500 × 6 ÷ 1,000 = 9 kWh. At 18.31 cents per kWh, the US average for July 2026 in EIA Table 5.6.A, 9 × 18.31 = 164.8 cents, or $1.65 a day, and 30 such days cost $49.44. Because the label gives the maximum, 9 kWh is the most that heater can use in those 6 hours. For the heater to pay, the central heat has to cost at least $1.65 less on each of those days.

The saving comes only from the rooms you let cool

In a home heated by electric baseboards, a plug-in heater makes no cheaper heat than the central system. EIA's March 2023 equipment study says electric resistance heating is considered 100% energy efficient, with all incoming electric energy converted to heat, and it counts wall and baseboard heaters as resistance heaters. EIA's resistance unit heater category excludes plug-in space heaters, so this example assumes the heater also turns each kWh into one kWh of heat. In a home heated by baseboards, a kWh in the heater and a kWh in a baseboard buy the same heat at the same price. So in the example, the baseboards in the other rooms have to use at least 9 kWh less on each 6-hour heater day.

The rest of the house cools only when you turn the central thermostat down. DOE's 2022 Energy Saver guide puts the saving from turning it down 7 to 10°F for 8 hours a day in fall and winter at as much as 10% a year on heating and cooling, the rule behind setting back a furnace thermostat. The heater's cost comes out of that saving. The same guide says electric heat can be more expensive than other fuel options, so in a gas-heated home the heater's heat can cost more than the furnace's. The night setback needs no heater at all: CPSC says to turn heaters off when sleeping.

With a heat pump, the plug-in heater makes the costlier heat

DOE's 2022 guide says heat pumps provide up to three times more heat than the energy they use, and can cut electricity use for heating by approximately 50% compared with electric furnaces or electric baseboard heaters. The heater gets no such multiplier. Its 9 kWh in the example becomes 9 kWh of heat under the example's assumption of one kWh of heat per kWh; a heat pump delivering three times its energy would make that heat from as little as 3 kWh, about 55 cents at the same 18.31 cents per kWh from EIA Table 5.6.A.

Turning a heat pump down has a catch: the same DOE guide says not to set back a heat pump's thermostat manually if that brings on backup electric-resistance heating, which is more expensive. In a heat pump home, hold the heat pump steady and leave the heater off unless the daily-use check below shows a saving.

Check the meter before you keep it

If your utility shows daily use online, compare a few days with the thermostat set back and the heater on against days of similar weather at your usual setting. With electric heat, the heater runs on the same meter, so the daily kWh total has to fall. With gas heat, two meters move: electric use rises by the heater's kWh, and gas use should drop. Price the gas at the gas bill's dollars divided by the gas it bills for, and the heater as in the example. Keep the heater if the gas saving is larger. If not, unplug it.

Plug it into the wall, keep three feet clear, turn it off at bedtime

CPSC's 23 January 2026 winter safety release estimates that portable heaters, including electric space heaters, are involved in an average of 1,600 fires a year, with an average of 70 deaths and 150 injuries a year from 2020 to 2022. The same release sets three rules for a plug-in heater:

• Plug it directly into a wall outlet, never into an extension cord or power strip.
• Keep it at least three feet from drapes, furniture, bedding and other combustible materials.
• Turn it off when you sleep.

Extension cords were often cited as the cause of heater incidents in CPSC's 2023 staff assessment. An outlet that feels hot, or a breaker that trips while the heater runs, is work for a licensed electrician; ask whether that circuit can carry a 1,500-watt heater. A kerosene or gas space heater is a different appliance: EPA's carbon monoxide page lists unvented kerosene and gas space heaters among indoor CO sources, so it belongs with CO alarms and a yearly inspection.