The oil in the radiator acts as a heat reservoir, which stays hot for some time after the heater's switched off. If you have the thermostat of your heater set to a desired temperature, the heater will toggle on and off once it reaches that temperature – depending on what's needed to maintain it. We've put electric heaters from Argos, Dimplex, DeLonghi, Dyson, Russell Hobbs and more to the test, including electric wall heaters, fan heaters, oil heaters and convectors. The oil also makes the heater heavy and they can be difficult to lift or move around, although many are equipped with wheels to make them more portable. Cost per hour is based on using the heater on its highest setting as, following our testing, we think this is the setting you're more likely to use.

Bring your dream home to life with expert advice, how-to guides and design inspiration, direct to your inbox. We assess how easily each electric heater can be set up and how easily understandable the controls and settings are. This means the electric heater will need to run at full blast for longer than your central heating, as it will have a tougher job keeping the room at the temperature you want. In addition, oil-filled heaters are up to 99% energy-efficient because they directly convert all the electric energy into heat energy with barely any losses. You then divide your weekly heating cost by the number of hours you have it switched on and compare that figure to the cost of running your heater.Brackets and instructions for wall mounting are usually included, but you'll need to drill holes in your walls. Smaller oil heaters can use as little as 500W of power (possibly less) and are designed to heat smaller rooms — while larger oil heaters can use 2,500W or more. Some modern options also have smart features so you can program them via companion apps and smart speakers. Our tests also found that they're rarely 100% accurate and will probably think the room is a couple of °C warmer or cooler than it is. However, many oil-filled radiators will come equipped with a built-in thermostatic control, which therefore allows you to control the power and heat output of the radiator.

We found the most drastic changes happen in the first half an hour and increases in temperature become more incremental after that. One of the biggest advantages of oil-filled panel heaters are their portability; it heats the areas of your house another conventional heater cannot simply because you can pick it up and move it there.

Nearly all have some kind of carry handle for moving about and many have a safety cut-out feature, which will switch off the heater if it gets dangerously hot.