Space Heater Running Cost Calculator

How it works

Cost per hour = watts ÷ 1000 × rate. Cost per day = cost per hour × hours used. Seasonal cost = cost per day × heating days per year. Electric resistance heaters are 100% efficient at the plug, so wattage directly drives cost — there is no cheaper or more expensive electric heater for the same heat output.

Worked example, step by step

Take the default numbers: a 1,500W heater run 5 hours a day for 120 heating days a year, on a $0.17/kWh electricity rate.

Cost per hour = 1,500W ÷ 1,000 × $0.17 = $0.255, about 26 cents.

Cost per day = $0.255 × 5 hours = $1.28.

Cost for the whole heating season = $1.28 × 120 days = $153.

That $153 is the full-season cost of using this one heater on this schedule — worth comparing directly against what the same hours of central heating or a heat pump would cost for the room(s) it covers, using the heat pump savings calculator or your own bill.

Why "efficient" space heaters don't actually save money

This surprises a lot of people: every electric resistance heater — ceramic, ceramic-fan, ceramic ("micathermic"), oil-filled radiator, infrared panel, ribbon element — converts essentially 100% of the electricity it draws into heat. A "1,500W eco heater" and a "1,500W basic heater" cost exactly the same to run for the same time, because wattage is wattage; there's no efficiency gain to be had among electric resistance heaters the way there is between, say, an old gas furnace and a new one.

The only ways to genuinely cut the cost are: using a lower-wattage heater (less heat, less cost, straightforward trade-off), running it fewer hours via a timer or built-in thermostat that cycles the element off once the room is warm, heating a smaller enclosed space rather than an open-plan room, or switching to a heat pump — which moves existing heat rather than generating it from electricity, and can deliver 2-4x more heat per dollar of electricity (see the heat pump savings calculator).

A built-in thermostat is worth paying extra for: a heater that cycles off once the room hits temperature can use meaningfully less energy over a session than one left running continuously at full power, even though the wattage rating is identical — the saving comes entirely from runtime, not from any difference in the heating element itself.

Frequently asked questions