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.
Written and checked by the RapidHeat UK team · Last updated September 2026 · how we work out running costs
Key takeaways
- 500–1,200 W heaters cost 14p to 32p an hour to run at 27p per kWh.
- Low wattage means slower warm-up, not lower cost per unit of heat.
- They are the right choice for small, insulated rooms and for hook-up limits in caravans.
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
A 500 W heater running for five hours uses 2.5 kWh and costs about 68p at 27p/kWh. A 1,200 W heater costs about 32p for each full-power hour, but may switch the element off after reaching the set temperature. Which uses less over an evening depends on the room, insulation, weather and thermostat setting. Power gets you to temperature; controls limit unnecessary run time.
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.
Getting the most from a low-wattage heater
- Draught-proof first: at 500 W you cannot outrun a gap under the door.
- Warm the space before it gets cold — recovering a cold room takes far longer at low power.
- Use a thermostat so it idles instead of running flat out.
- Close the room off; a low-wattage heater cannot heat two rooms through an open door.
Two heat settings beats one
The practical answer for most people is a heater with both a higher and a lower setting: use the higher one to bring the room up, then drop to the lower one to hold it. That is how RapidHeat is set up — 1,200 W to warm the room, a lower setting plus the thermostat to keep the running cost down once you are comfortable.
RapidHeat ceramic heater
4.8/5 · 1,247 UK customers£49.95· £89.91 for two · £110.89 for three (about £36.96 each)
- Thermostat, timer and remote
- Warm room in about 5 minutes
- Free tracked UK delivery
- 30-day money-back guarantee
Perfect for my cold office
I have a small office with a door that gets really cold because the building management keeps the winter temperature far too low for comfort. I plugged this into the socket above my desk and now I am warm without anyone even knowing it is there. I love it.
Great in the bathroom
We use it to take the chill off the bathroom before the kids' bath time. Warms up fast and the timer is handy. Four stars only because I wish the display were a little dimmer at night.
Worth being straight about: RapidHeat is built for rooms up to about 12 m². It is not a replacement for central heating and it will not transform an open-plan lounge or an uninsulated garage. If it is not right for your room, send it back within 30 days.
Questions people ask
- Is a 500 W heater enough for a room?
- For a very small, well-insulated space such as a cloakroom, a cabin bed area or under a desk, yes. For an average bedroom it will struggle to raise the temperature much on a cold night.
- Do low wattage heaters save money?
- They cost less per hour, but they also deliver less heat per hour. If a 750 W heater has to run twice as long to get the same result as a 1,500 W one, you have saved nothing. The saving is real when the smaller heater is genuinely enough for the space.
- What is the lowest wattage heater worth buying?
- Below about 400 W you are buying a personal warmer. Between 500 W and 1,000 W you can hold a small room at a comfortable temperature once it is warm, especially with a thermostat.
- Which low wattage heater is best for a caravan?
- Something you can run at 500–1,000 W, so it fits a 6 A or 10 A hook-up alongside a kettle. A heater with selectable power levels is more useful on site than a single-speed unit.
Ready to warm your room in about 5 minutes?
Order RapidHeat today with free tracked UK delivery and a 30-day money-back guarantee.
Sold direct by RapidHeat UK. Secure checkout, free tracked UK delivery.