Quick answer
For most UK rooms up to 20 m², a small 1200W ceramic space heater with a thermostat is the sweet spot. It's powerful enough to warm the room quickly and cheap to run once the thermostat takes over. The shoebox-sized Ofenwerk K1 fits that brief.
Quick checklist
- Compact footprint that fits on a desk, shelf or floor
- 800–1500W, so it isn't too powerful for the space
- Thermostat to stop the room getting stuffy
- Cool-touch casing for tight spaces
- Tip-over switch
What size heater do I need?
A rough rule is 60–100W per m², depending on insulation. Most UK bedrooms (9–15 m²) and living rooms (15–20 m²) suit a 1000–1500W heater. Going bigger usually just wastes energy.
| Room | Typical size | Suggested power |
|---|---|---|
| Box room / study | 6–9 m² | 800–1000W |
| Bedroom | 9–15 m² | 1000–1200W |
| Living room | 15–20 m² | 1200–1500W |
| Open-plan | 25 m²+ | Two heaters |
Features worth paying for
- Ceramic PTC element: fast and self-regulating
- Thermostat
- Safety cut-offs
- Remote control
- Quiet operation
Small heater, big savings
A small heater lets you zone your heating. Keep the room you're in warm and turn the rest of the house down.
What it costs to run (current UK prices)
At the Ofgem price cap of 26.32p per kWh (1 October to 31 December 2026), a 1200W heater like the K1 costs about 32p an hour at full power. Once the room is warm the thermostat switches the heater on and off, so in normal use it averages about 16p an hour.
| How long | Typical cost per day | Over 30 days |
|---|---|---|
| 1 hour | 16p | £4.74 |
| An evening (4 hours) | 63p | £18.95 |
| A working day (8 hours) | £1.26 | £37.90 |
Your own price may be a little higher or lower depending on your region and tariff. See how we calculate running costs or try the running cost calculator with your own unit rate.
What counts as a small space?
Box rooms, studies, en-suites (with a heater rated for bathrooms only), utility rooms, garden offices and student rooms are usually 4–10 m². In a space that size, a 1200W heater on its thermostat will warm the air in a few minutes and then mostly switch on and off.
Avoid these small-space mistakes
- Buying a 2–3kW heater for a box room. It overheats the space and costs more
- Putting the heater under a desk next to papers or a bin
- Running it in a bathroom unless it's IP-rated for bathrooms (the K1 is not)
- Leaving it on in a closed room with no ventilation for hours
Garden offices and sheds
Garden rooms lose heat quickly through thin walls and glass. A small heater works well if the building is insulated and has a proper outdoor-rated power supply. In an uninsulated shed you'll feel the heat near the heater but the space won't hold warmth.
How the K1 compares with other heaters
| Heater type | Warm in | Running cost | Safety and comfort |
|---|---|---|---|
| Ofenwerk K1 (ceramic) | About 2 seconds | About 16p/hour typical | Tip-over and overheat cut-off, cool-touch case, no glowing coil |
| Coil fan heater (2–3kW) | Seconds | 53–79p/hour at full power | Hot coil, can smell of burnt dust, often noisy |
| Oil-filled radiator (1.5–2.5kW) | 20–30 minutes | 39–66p/hour at full power | Surfaces get hot, heavy to move |
| Convector (2kW) | 10–15 minutes | About 53p/hour at full power | Heat rises to the ceiling first |
| Electric blanket (100W) | 10–20 minutes | About 3p/hour | Warms the bed only, not the room |
Full-power costs worked out at 26.32p per kWh. Thermostats lower all of these in real use.
Using any electric heater safely
These tips follow UK fire-service and Electrical Safety First advice and apply to any portable heater, including ours:
- Plug the heater straight into a wall socket. Don't use an extension lead or adaptor; they can overheat.
- Keep it at least 1 metre from curtains, bedding, clothes and furniture.
- Stand it on a flat, hard, stable surface where it can't be knocked over.
- Never cover it or dry clothes on it.
- Switch it off at the wall when you go out.
- Check the plug and cable now and then. Stop using it if either is damaged or feels hot.
- Make sure you have a working smoke alarm on every floor. Many UK fire services fit them free for older residents.
When the K1 is not the right choice
We'd rather you buy the right heater than return ours. The K1 is probably not for you if:
- You want to heat a large open-plan space over about 20 m² with one heater. Two K1s, or a bigger heater, will do a better job.
- You need a heater for a bathroom or wet room. Choose one designed and rated for bathrooms.
- You need total silence. The K1 has a gentle fan sound, a bit like a quiet laptop.
Our pick: the Ofenwerk K1 Heater
- Warm air in about 2 seconds (PTC ceramic)
- 1200W, heats rooms up to 20 m²
- Tip-over and overheat cut-offs, cool-touch casing
- Thermostat + remote, about 16p an hour typical
- Free UK delivery, 30-day money back, 24-month warranty
Frequently asked questions
Are small space heaters any good?
Yes, for rooms up to about 20 m². For bigger spaces, use two.
What is the safest small space heater?
Look for tip-over and overheat cut-offs, a cool-touch casing, and a sealed ceramic element with no glowing coil.
What size heater do I need for a small room?
Around 100W per square metre is a common guide. An 8 m² room needs about 800W, but a 1200W heater with a thermostat gives faster warm-up and then cycles down.
Is a small heater cheaper to run?
A lower-wattage heater uses less energy per hour. In a small room any heater with a thermostat will spend much of its time switched off once the room is warm.
Can I use a small heater on a desk?
Yes, if it's stable, has a tip-over switch and there's clear space around it. Keep papers and fabric away from the air outlet.
Will a small heater warm a garage?
Only the area right in front of it. Garages are usually uninsulated, so the heat escapes quickly.
Sources and how we checked this guide
- Electricity price: Ofgem: energy price cap unit rates and standing charges, checked 25 October 2026.
- Heater safety: UK fire and rescue service advice and Electrical Safety First guidance on portable heaters.
- K1 figures (1200W, about 2-second warm-up, room size up to 20 m², safety cut-offs) come from the product specification.
- Costs are worked out with the method on how we calculate running costs.