How many watts does an oil-filled radiator use?

By Tom Calder · Figures checked 4 November 2026 · Costs at 26.32p per kWh (Ofgem cap, 1 October to 31 December 2026)

In short

An oil-filled radiator such as De’Longhi’s Radia S TRRS0715E draws 700W, 800W or 1,500W depending on the setting. An hour costs at most 18p to 39p at 26.32p per kWh, and less once the thermostat starts cycling.

A kettle coming to the boil beside a microwave and slow cooker in a warmly lit kitchen on a rainy evening

The numbers

Running watts: 700W to 1,500W; De’Longhi Radia S TRRS0715E: 700W, 800W and 1,500W settings. Larger models are made up to 2kW and more.
Amps at 230V (most): 6.5A
Energy an hour: 0.7 to 1.5 kWh; The lowest and highest settings for an hour. The thermostat cycles, so this is the most an hour can cost.
Cost an hour: 18p to 39p
On a 1kWh power station: 30 minutes to 1 hour
On a 2kWh power station: 1 to 2 hours

Costs use 26.32p per kWh, the Ofgem price cap's average Direct Debit electricity unit rate for 1 October to 31 December 2026. Your own rate is on your bill; on a fixed or time-of-use tariff it will differ.

How it’s used, and what that costs

An oil-filled radiator costs the same per unit of heat as any electric heater. What it does differently is store heat in the oil, so it warms up slowly and keeps giving out heat for a while after it switches off. Electrical Safety First suggests warming a bedroom with one before bed, rather than leaving a heater on overnight.

The honest bit

It is no cheaper per hour than a fan heater of the same wattage; the difference is gentler, quieter heat. The safety rules for any plug-in heater are in our electric heater safety and running costs guide.

In a power cut: how long a power station would run it

A 1kWh power station: 30 minutes to 1 hour. A 2kWh power station: 1 to 2 hours. These use the same planning method as our power station pages: capacity × 90% usable depth × 85% inverter efficiency, divided by the load plus about 10W the unit uses itself (BLUETTI’s UK formula).

Output matters as much as capacity. The 7 units around 1kWh we list supply 1,500W to 2,000W continuously, and the 6 around 2kWh supply 2,200W to 3,000W, so check a unit’s rated output covers 1,500W before you rely on it.

On a power station it is a poor bet: even the low setting empties a 1kWh unit in about an hour. Never bring a barbecue, camping stove or patio heater indoors. Use a gas or paraffin heater only if it is made for indoor use, with ventilation and a working carbon monoxide alarm (NHS).

To size one for everything you’d want to keep running, use the sizer on our power stations comparison.