How Much Does It Cost to Run an Oil-Filled Radiator?

Plug-in heaters in the US and Canada top out at about 1,500 W on a standard 120 V outlet. De'Longhi's Dragon 4 for North America, for example, is rated at 1,500 W at 120 V.

In 230 V countries, such as the UK, Ireland, the rest of Europe and Australia, larger models are common. De'Longhi's 6-fin Dragon 4 runs at 700–1,500 W and its 10-fin version at 1,100–2,500 W, each with three settings.

At our assumed 0.75 kWh an hour, 8 hours a day uses 6 kWh: about $1.09 in the US, £1.58 in the UK and €2.17 in Germany. Over a month that's about 182 kWh, or £48.01 in the UK.

In a cold or draughty room the element may hardly switch off, and the cost approaches the full 1.5 kWh an hour. In a small, well-insulated room it can be lower than our figure.

The oil is sealed inside and never needs topping up. It isn't burned or used up: it's a heat store that the element warms.

Because the oil holds heat, the radiator takes a while to warm up and keeps giving off heat after the element switches off. That makes the heat gentle and quiet, but it doesn't turn a kWh of electricity into any more heat.

The thermostat is what saves money, by switching the element off once the room reaches the set temperature. The South Australian Government says every degree lower on a heater's thermostat can cut running costs by up to 10%.

Some models add a timer or an ECO mode, which help stop the radiator heating an empty room.

Every electric resistance heater turns 1 kWh of electricity into 1 kWh of heat. Natural Resources Canada describes electric resistance heating as typically 100% efficient, so an oil-filled radiator gives no more heat per kWh than a fan heater or convector of the same wattage.

The differences are comfort and control. Oil-filled radiators are silent and warm a room evenly; fan heaters warm a small space faster.

A heat pump uses much less electricity for the same heat. ENERGY STAR says ductless mini-split heat pumps use up to 60% less energy than standard electric radiators.

For one person sitting still, an electric blanket or heated throw uses a fraction of the power. Heating season runs roughly from November to March in the Northern Hemisphere and from June to August in Australia, New Zealand and South Africa.

Ranges are for named De'Longhi models; other brands are similar. Your radiator's rating is on its label. In the calculator, enter that rating and the share of time the element is on (we assume 50%).

• Set the thermostat as low as is comfortable; each degree lower saves money.
• Warm the room on high, then turn down to a lower setting or let the thermostat take over.
• Use the timer to warm the room shortly before you need it instead of running the radiator all day.
• Close doors and curtains and stop draughts, so the element switches off more often.
• Heat only the room you're in. For one person sitting still, an electric blanket or heated throw costs far less.
• If you heat a room for many hours a day, a heat pump (reverse-cycle air conditioner) can cut the energy needed by up to 60%.

• Space heater
• Electric blanket
• Heat pump
• Kotatsu
• Bill analyzer