Electric Heaters: Fan, Oil-Filled, Infrared & Electric Fires

All electric heaters are 100% efficient, so a 2kW heater of any type costs the same to run at the same wattage. At around 26p per kWh, a 2kW heater costs about 52p an hour at full power. The cheapest heater to run is therefore the lowest-wattage model that still keeps your room comfortable, paired with a good thermostat and timer so it isn't drawing power once the room is warm.

It depends entirely on the wattage and how long they run. At about 26p per kWh, a 1kW heater costs roughly 26p an hour, a 1.5kW about 39p, and a 2kW about 52p. Used sensibly to heat one occupied room rather than the whole house, an electric heater can be cheaper than firing up central heating, especially with a thermostat and timer keeping the on-time down.

No single type is inherently cheaper, because all electric heating converts electricity to heat with equal efficiency. What differs is how the heat is delivered. Oil-filled radiators hold warmth after switch-off, infrared heats people and objects directly so you can run it less, and fan heaters give quick bursts. Choosing the type that lets you run fewer watts for less time is what actually lowers your bill.

Multiply the heater's kilowatt rating by your electricity price per kWh. At roughly 26p per kWh, a 1kW heater costs about 26p an hour, a 1.5kW about 39p, and a 2kW about 52p at full power. A thermostat reduces this in practice, because the heater cycles off once the set temperature is reached rather than running flat out the whole time.

Not at the same wattage. A 2kW oil-filled radiator and a 2kW fan heater cost the same per hour to run. The difference is in behaviour: oil-filled radiators heat up and cool down slowly, giving silent, even warmth that lingers, which suits rooms you occupy for hours. Fan heaters deliver instant heat for short bursts. Choose based on the room and how long you need heat, not on assumed running cost.

An infrared heater rated at, say, 1.5kW uses the same electricity as any other 1.5kW heater while it's running. The potential saving comes from how infrared works: it warms people and surfaces directly rather than heating all the air, so in draughty or open spaces you can often feel comfortable while running it for less time or at a lower setting. In a small, well-sealed room the advantage is smaller.

As a rough guide for a reasonably insulated UK room, allow about 100 watts of heating per square metre. That means roughly a 1kW heater for a small bedroom or study, and 1.5–2kW for a typical living room. Rooms with poor insulation, large windows or high ceilings need more, while a snug, well-sealed space needs less. Sizing up unnecessarily just increases your running costs.

Modern electric heaters with tip-over protection, overheat cut-outs and a thermostat are designed to run safely, and many people use oil-filled radiators overnight on a low thermostat setting. To stay safe, keep the heater on a hard, level surface, well away from bedding, curtains and furniture, never cover it, and don't run it from an extension lead. If you want extra peace of mind, use a model with a timer or frost-protection setting rather than leaving it on full.