Heater types
Low wattage heaters, including 500W
The short answer
Low wattage sounds like low cost, and per hour it is. The catch is that a heater too weak for the room never reaches a comfortable temperature, so it runs for hours and still costs you money.
Cost per hour by wattage
Based on a unit rate of about 27p per kWh. Five hours is a typical winter evening. These are full-power figures — a heater with a thermostat will cycle off and use less.
| Heater power | Per hour | Five hours | What it realistically does |
|---|---|---|---|
| 500 W | 14p | £1.35 | Chill off a very small room, frost protection |
| 750 W | 20p | £2.03 | Box room, en-suite, under a desk |
| 1,000 W | 27p | £2.70 | Small bedroom or home office |
| 1,200 W | 32p | £3.24 | Room up to about 12 m² |
| 1,500 W | 41p | £4.05 | Larger bedroom or small lounge |
| 2,000 W | 54p | £5.40 | Living room, but often overkill |
Is a 500W heater enough?
For frost protection in a shed or hallway, yes. For keeping your feet warm at a desk, yes. For making a 9 m² bedroom comfortable on a January evening, usually not — heat leaves the room faster than 500 W can replace it, so the temperature plateaus a few degrees above where it started. The heater is not faulty; it is simply too small for the job.
Why higher power can cost less
Compare two evenings in the same 10 m² room. A 500 W heater runs for five hours, never reaches your target, and costs about £1.35 for a room that is still chilly. A 1,200 W heater with a thermostat reaches temperature in five minutes, then cycles at roughly a third of full output for the rest of the evening — perhaps 1.5 kWh, or about 41p — and the room is genuinely warm. Power gets you to temperature; the thermostat is what keeps the bill down.
Matching power to room size
- Up to 8 m²: 500–1,000 W
- 8–12 m²: 1,000–1,500 W
- 12–20 m²: 1,500–2,000 W
- Over 20 m² or open plan: central heating, not a plug-in heater
Add power for high ceilings, single glazing, solid walls or an external door. Detailed working in the small room heater guide.
Where low wattage is exactly right
- Greenhouses that only need to stay above freezing.
- Sheds and workshops where you want to protect tools from damp.
- Caravans on hook-up with a limited amp supply.
- Desks, where you are heating a person rather than a room.
How RapidHeat handles this
RapidHeat has enough output to bring a room up to about 12 m² to temperature quickly, then the thermostat drops it back so it is not drawing full power all evening. You get the speed of a properly sized heater with running costs closer to a low wattage one. The timer means it only runs during the hours you actually want warmth.
Ready to warm your room in about 5 minutes?
Order RapidHeat today with free tracked UK delivery and a 30-day money-back guarantee.
