Does a plug-in heater use a lot of electricity?

The simple formula

Cost per hour = (watts ÷ 1000) × your price per kWh.

For example, at 800W and a price of 0.20 per kWh, that's 0.8 × 0.20 = 0.16 per hour. At 400W it's half that. The thermostat also cycles the heater off once the room is warm, so the real cost is often lower.

How to keep costs down

• Use the low mode once the room is warm
• Set the thermostat instead of running it flat out
• Use the timer
• Close the door to keep the heat in

Watts, kilowatts and kWh, made simple

A heater's wattage tells you how much power it draws while it's running. 1,000 watts is one kilowatt (kW). If a 1 kW heater runs for one hour, it uses one kilowatt-hour (kWh), which is the unit on your electricity bill.

So an 800W heater uses 0.8 kWh per hour at full power, and a 400W heater uses 0.4 kWh. A typical 1,500W space heater uses 1.5 kWh per hour, nearly twice as much as RapidHeat on High.

Why the real cost is often lower

Heaters with a thermostat don't run at full power all the time. Once the room reaches the temperature you've set, the heating element cycles off and on to hold it. In a well-closed room, that can mean it's actually heating only part of each hour.

Draughts, open doors, thin windows and cold outside temperatures make it work harder. Close the door and curtains and you'll use less.

Plug-in heater vs central heating

Per unit of energy, electricity often costs more than gas. But central heating warms every room, including those you're not using. A small electric heater in one room can be cheaper overall when you turn the main heating down. Whether it is for you depends on your prices and home, so it's worth running the numbers.

Signs your heater is costing too much

• It runs on full power for hours without the room feeling warm
• The room is much bigger than the heater is designed for
• Doors or windows are left open
• It's on while nobody's in the room

How many heaters for your room?

A rough guide for topping up a home that has some heating. Cold, high-ceilinged or poorly insulated rooms may need more.

What it costs to run

Maximum cost at full power, for common electricity prices per kWh in your own currency. With the thermostat cycling off once the room is warm, real costs are often lower. Try the energy cost calculator with your exact price.

Who RapidHeat is not for

We'd rather you buy the right heater than return the wrong one. RapidHeat isn't the best choice for:

• Heating a whole house or open-plan floor on its own
• Large rooms over about 250 sq ft (≈23 m²) with just one unit (use two or more)
• Bathrooms or anywhere it could get splashed with water
• People who want silent, fan-free heat (try an oil-filled radiator)

Common questions