As winter heating bills climb, shoppers are bombarded with promises of ‘low-consumption’ electric heaters. The physics tells a simpler story: every device that heats with a resistive element converts electricity into heat at essentially the same rate, so no manufacturer can squeeze more warmth out of a kilowatt-hour than a rival. The only technology that clearly uses less power for the same heat output is the heat pump. Understanding that distinction is the fastest way to avoid paying a premium for marketing rather than performance.
- Identical efficiency: Resistance heaters convert all incoming electricity into heat, meaning no model outperforms another on raw conversion.
- Simple maths: Multiply rated power in kilowatts by hours of use to get kilowatt-hours, the unit billed by utilities.
- Heat pumps win: They move heat from outside instead of generating it, cutting electricity demand by roughly half.
- Safety first: Fire services urge plugging heaters directly into wall sockets and keeping flammable material at least one metre away.
How much power does a heater actually draw?
The calculation is straightforward. A device consumes at most one unit of electricity per hour for every kilowatt of rated power, so a 2 kW unit tops out at 2 kWh each hour. A 2,000 W heater running five hours a day therefore uses about 10 kWh daily. At an illustrative rate of 0.15 euros per kWh, that works out to roughly 1.50 euros a day, or around 45 euros over a 30-day month.
That figure is a ceiling, not a guarantee. Thermostat-equipped models cycle the element on and off once the room reaches the target temperature, so real consumption drops. Room insulation ultimately determines how many of those hours the heater runs at full tilt. A second number matters too: contracted household power. With only 3 kW available, running a fan heater and a hairdryer simultaneously can trip the breaker.
Oil radiators, convectors and ceramics: what really differs
Since the kilowatt-hours stay the same, the meaningful differences lie in speed, noise and where the warmth is felt. Fan heaters are light and extremely fast, well suited to briefly warming a small space, and their surfaces are hard to burn yourself on, though they are not built for long sessions. Convectors also use hot air but run quieter and are less portable; they heat quickly and tolerate long runtimes, yet their metal casing gets very hot. Oil-filled radiators mimic traditional radiators: heavy, slow to respond and not always precise with their thermostats. Halogen or infrared units do not heat the room at all, warming only the person in front of them.
Ceramic models, so-called thermal emitters and ‘low consumption’ designs may distribute heat differently, but none escapes the underlying rule: a resistive element delivers the same heat per kWh. Manufacturers argue that oil radiators are cheaper to run because they retain heat and cycle the element less often. That changes when you consume power, not how much heat the room requires; if a space loses heat, it must be replaced regardless of the technology.
When a heat pump makes more sense
For long daily heating sessions, a heat pump is the better investment. Because it moves existing heat from outdoors rather than generating it, it can readily cut electricity use by around 50 percent compared with resistance heating. The trade-off is cost and installation, which bear no resemblance to unboxing a portable appliance and plugging it in.
The practical decision therefore depends on use. A few minutes in a bathroom or a short stint in a home office calls for a fan heater: fast and cheap to buy. Several hours in one room suits a convector or oil radiator, ideally with a thermostat and timer. Whole-home electric heating points to a heat pump, and households with existing central heating may first want to check how much a smart thermostat can genuinely save.
Fire safety and product alerts
Fire services are blunt about extension leads: don’t use them. In a public safety campaign, the fire brigade of the Community of Madrid urged users to connect heaters directly to wall outlets to prevent overloads, given their high power draw. If a power strip is unavoidable, it should be certified and carry few devices.
Official civil protection guidance converges on the basics. Keep any easily flammable material at least one metre from heaters and never drape wet clothing over them. Keep units away from curtains, furniture and especially beds or mattresses, and never use an appliance that smells strange when switched on or appears damaged. Sockets should be dry and, preferably, earthed. Smoke detectors belong in the living room, near bedrooms and at least one per floor.
One detail rarely covered in buying guides: a unit can arrive faulty from the factory. In 2025, small appliances including electric braziers and hairdryers accounted for 8.7 percent of dangerous-product alerts processed in Spain, according to consumer ministry statistics. Buying from identifiable sellers and keeping the receipt matters.
Ultimately, an electric heater is a support tool, not a heating system, and ‘low consumption’ marketing obscures that fact. No miracle material rewrites the physics of resistance: what lowers the bill is running the device fewer hours, in smaller and better-insulated rooms, or switching to a heat pump for daily use. Before buying a third radiator, households should check whether they qualify for social electricity tariff discounts, which for many homes save more than any appliance ever will.