How much does a space heater cost to run?

RapidHeat running cost calculator

Enter your electricity price and how long you use the heater. Pick Low or High mode and how many heaters you'll run. The results update straight away.

The formula (works for any heater)

Cost per hour = watts ÷ 1000 × price per kWh. A kilowatt-hour (kWh) is 1,000 watts running for one hour. So an 800W heater uses 0.8 kWh in an hour on full power, and a 1500W heater uses 1.5 kWh. Multiply by your price and you have the hourly cost. Multiply by hours per day and days per month for your bill estimate.

How to find your price per kWh

Look on your latest electricity bill or in your supplier's app for the "unit rate", "energy charge" or "price per kWh". Ignore the daily standing or service charge, because it doesn't change with how much you use. If you have a day/night tariff, use the rate for the hours you'll heat. If you can't find it, the quick-pick buttons (0.15, 0.25, 0.35) cover the range many households pay, in their own currency.

Heater running costs compared

Maximum cost per hour at full power. Same formula for every heater, no invented savings.

A bigger heater gives out more heat as well as costing more, so it warms a large room faster. RapidHeat costs less per hour because it's sized for one small-to-medium room (up to about 250 sq ft / 23 m²), not because watts work differently.

Worked examples

All at 0.25 per kWh, maximum cost:

• Evening in the bedroom: High for 3 hours = 0.60 a night, about 18.00 a month.
• Home office day: Low for 8 hours = 0.80 a day, about 17.60 for 22 working days.
• Overnight on Low with the timer at 6 hours = 0.60 a night.
• Two heaters on High in a living room for 4 hours = 1.60 a day.

One room or the whole house?

A small heater saves money when it lets you heat the one room you're using and keep the main heating lower or off. That's common for home workers, people living alone, or a cold bedroom at the end of the house. It doesn't save money if you try to heat a whole house with several plug-in heaters running all day, because electricity often costs more per unit of heat than gas or a heat pump. Use RapidHeat as a top-up, not a replacement for central heating.

6 honest ways to cut your running cost

• Set the thermostat to a comfortable temperature rather than the maximum, so it cycles off sooner.
• Use the timer so it switches off after you fall asleep or leave the room.
• Start on High to warm up quickly, then drop to Low to hold the temperature.
• Close the door. A closed room holds heat far longer than an open one.
• Block draughts at doors and windows, and close curtains after dark.
• Turn the main heating down in rooms you aren't using.

Why your real cost is usually lower

The calculator assumes full power for every hour you enter. In practice, once the room reaches your set temperature, RapidHeat's thermostat switches the heating off and on to hold it there. How much that saves depends on the room size, insulation and how cold it is outside, so we don't quote a percentage. Treat the numbers above as the most you'd pay. Want to see if it suits your room? Check the specs or see bundles and prices.