A plug-in electric heater costs little to buy and warms a room quickly, which makes it tempting in a cold snap. What the price tag hides is that electric heating is one of the most expensive ways to make warmth there is, so a cheap heater can run up a startling bill if you use it as a main source. Used cleverly, though, it can genuinely save money. The difference is all in how and when you reach for it.
Why electric heat is expensive
Every plug-in heater is essentially the same on cost: it turns electricity into heat at full efficiency, so a two-kilowatt heater uses two kilowatt-hours an hour whatever its shape or marketing. The expense is not inefficiency but the price of the fuel, because electricity costs several times more per unit than the gas a central heating boiler burns. So heating a room electrically costs far more than heating it with gas, even though the heater itself was cheap. Put a typical heater's wattage and a few hours a day into the running cost calculator and the figure is sobering.
When a portable heater actually saves
Despite all that, there is a real case for one. If you are spending the evening in a single room while the rest of the house sits empty, heating just that room with a portable heater can cost less than firing up the whole central heating system to warm the entire house. The trick is that you are heating one small space instead of many, so even at the dear electric rate the total can come out lower. This is the heater's proper job: spot-heating one occupied room, not replacing the central heating for the whole home.
Heat the person, not the room
The cheapest electric warmth of all heats you rather than the air. A small radiant or halogen heater pointed at where you sit, or a low-wattage heated throw or electric blanket, warms you directly for a fraction of the power needed to bring a whole room up to temperature. A heated throw might draw a hundred watts or so against a fan heater's two thousand, an enormous difference for similar comfort if you are sitting still. As the electric blanket guide covers, heating the body is often the smartest electric heating there is.
Do the types differ on cost?
For the same wattage, all electric heaters cost the same to run for a given time, because they all convert electricity to heat completely; the watts on the label decide the cost, not the technology. What differs is how the heat feels and how it is delivered. A fan heater warms a room fast but noisily and stops the moment it is off. A convector or oil-filled radiator heats more gently and evenly and an oil-filled one stays warm a while after switching off. A radiant or halogen heater warms objects and people in its line of sight quickly, which suits spot-heating. Choose by how you want the heat, then control the cost through the wattage and the hours, not by hoping one type is secretly cheaper.
Keeping the bill in check
If you use a portable heater, run it on a thermostat or timer where it has one, so it is not blasting at full power once the room is warm, and pick the lowest setting that keeps you comfortable. Close the door to keep the heat in the room you are paying to warm, and combine it with the free measures: a draught-sealed room and a closed curtain hold the warmth so the heater works less. And never leave one running in an empty room, since at the electric rate that is money burned for nothing.
The honest place for them
A portable electric heater is a targeted tool, not a heating system. It earns its keep warming one occupied room when heating the whole house would be wasteful, or warming you directly while you sit, and it costs you dearly if used as a substitute for properly sorted-out central heating. Get the heating controls, draughts and insulation right first, and keep the plug-in heater for the genuine spot-heating job it is good at.