Oil-filled radiators vs thermal emitters: same cost, different heat retention

Oil-filled radiators or thermal emitters: the efficiency is the same

A flat that isn't cold, two 1500 W oil-filled radiators on wheels, and a recurring question: do ceramic emitters save more than oil-filled radiators? The technical answer is uncomfortable for marketing: any electric resistance converts 100% of the energy into heat. There is no superior performance. The real difference lies in thermal inertia: an oil-filled radiator takes time to heat up, but keeps the temperature steady; a convector heats quickly and cools just as fast. The cost in euros per kilowatt is identical.

The myth of 'blue heat' and ceramic emitters

Thermal emitters and oil-filled radiators consume exactly the same at equal power. So-called blue heat is no more efficient: it uses a gel denser than oil to give a more stable sensation of warmth, but the meter can't tell the difference. The only advantage of modern emitters is zoned thermostatic control and time programming, which lets you adjust consumption to cheaper tariff hours. Without that management, the savings are zero.

How much does it cost to heat a home with electricity?

The real cost depends on the price of the kilowatt hour. A 2000 W radiator uses 2 kWh for every hour of continuous operation. At €0.20/kWh, that's €0.40 per hour. A 12.5 kg butane bottle costs €17.49 and delivers about 49,608 kJ/kg, which works out at €0.102/kWh. A butane heater runs at half the cost of any electric radiator. A heat pump is in another league: according to a calculation doing the rounds in the thread, with a COP of 4.5, each electric kilowatt produces 4.5 kW of heat. The cost per useful kWh drops to €0.018, ten times less than an electric radiator.

The mistake of moving the radiator from room to room

Dragging a 1500 W oil-filled radiator from the bedroom to the living room is throwing money away. The oil takes time to reach its working temperature, and when you move it, all the stored energy is lost. The ideal use is to keep it on in a room at low cost, not as a portable heat source. To heat a room quickly, a cheap 20 or 25 euro convector does the job better: it gives instant heat and stops consuming when you switch it off.

Insulation and habits: the lever that really matters

The best energy is the energy you don't need. Exceptional insulation reduces demand to the point where a heat pump can heat 310 m² with a consumption of 2.25 kW per hour. For flats without insulation, the frugal strategy is to heat the person, not the house: a blanket, warm clothes and closed doors. Days of extreme cold can be counted on the fingers of one hand: about ten a year at most.

With these numbers, the conclusion is simple: if you already have oil-filled radiators, don't swap them for thermal emitters expecting to save. The initial outlay of 75 euros for a new radiator is never recovered. Energy efficiency isn't in the appliance, but in how and when you use it.