If you're thinking about buying an oil-filled column heater, here's what to consider.

Size

Assuming the ceiling and walls are properly insulated, a 2.4kW model will keep a large lounge or open-plan living area reasonably well heated. For a smaller lounge a 2kW model should do the job. If want to keep the chill off a bedroom, go for a 1kW or 1.5kW heater. Use our calculator, to work out exactly what size heater you need for a particular room.

Performance

Oil-filled heaters work by convection: they warm the air, which rises and gathers at ceiling level. Models with a built-in fan will mix the air better, resulting in a more even room temperature.

Controls

The controls should be clearly visible, easy to access and easy to use. Markings should be easy to read with good contrast. The more heat settings the better - you'll have more flexibility to control the room temperature.

Timer

With a timer, you can warm up a living area before your get up in the morning or arrive home from work. You can also have a bedroom heater turn itself off after you've gone to sleep.

Fan

A fan is an effective way to break up the layers of cold and warm air in a room. While noisy, you don't have to use them continuously. Just switch them on for a few minutes, to warm up the room.

Frost watch

This apparently maintains a temperature of 5°C if the thermostat is left on its lowest setting, avoiding frost. We can't quite see the purpose, unless you want to keep your heater in the glasshouse, or maybe in a conservatory, to protect special plants from frost damage.

Mobility

Oil-filled heaters are heavy and can be difficult to move around because of their size and shape. Try moving the heater around in the shop. There is usually a recessed handle at the control panel end: it should give a good grip.

Some models have four castors, others a combination of castors and wheels. Some have a single pair of large wheels at one end, so you have to lift the handle end to move the heater. Weight then becomes important.

Clothes drying

Clothes must not be draped over an oil-filled heater or it could overheat. Some heaters come with a detachable drying rack that spaces the clothes away from the heater. For others, you can buy a separate drying rack.

Radiant heat

Oil-filled heaters don't normally produce much radiant heat. But some models have an extra element designed to rapidly heat the outer surface of the fins. If you're sitting nearby, it won't take so long for you feel to some warmth directly from the heater. But it's not designed to make the whole room warm any faster.

Safety

There are several safety issues to consider. The relatively low surface temperature makes oil-filled heaters safer than most other types of heater.

But some models, following early designs, have narrow exposed fins that get quite hot. Safer, these days, are the models with wide flat fins, or a casing over the fins, and a protective heat shield at each end.

Because they are tall and narrow, column heaters are inherently less stable than other types. They are also heavy. If a model with narrow exposed fins topples onto a small child, it can do quite a lot of harm. Having wide or enclosed fins helps. A tapered shape may help stability.

If there are toddlers about, a loop of chain around the top fin tube and attached to a wall could stop a nasty accident if the child tried to pull the heater over.

Tilt switch

This is a very useful safety feature - it will turn the heating element off if the heater overturns. We think it should be a standard feature on all heaters, but unfortunately it has become increasingly rare on all but the most expensive models.

Thermal cutout

Some models have a built-in thermal cutout, to turn the heater off if it overheats.