Room by room
Heating a shed, workshop or garden room
The short answer
There are two very different jobs here: keeping a building above freezing and dry, and making it comfortable enough to work in. They need different settings and cost wildly different amounts.
Written and checked by the RapidHeat UK team · Last updated September 2026 · how we work out running costs
Key takeaways
- Frost protection needs very little power — comfort needs a lot more.
- A thermostat set just above freezing is the cheapest way to protect tools, paint and plumbing.
- Never run a shed heater from a long, coiled extension lead.
Job one: frost protection and damp control
Tools rust, paint spoils and stored equipment suffers because of damp and freezing, not because a shed is chilly. Gentle background heat with a thermostat set low — around 5°C to 8°C — keeps surfaces above dew point on most days. A 500 W to 800 W heater cycling occasionally may only use a few kilowatt-hours a week, which is pence per day at a 27p unit rate. See low wattage heaters.
Job two: working comfort
For hobby time in a timber shed, size the heater to the space and accept that a poorly-insulated building needs continuous input:
- Small insulated shed or garden office up to 8 m²: 1,000–1,200 W
- Workshop 8–14 m² with some insulation: 1,500–2,000 W
- Uninsulated timber shed: spot heating only, whatever the wattage
Insulation beats wattage
A shed lined with insulation board and a breathable membrane holds warmth for hours. The same shed bare loses it in minutes. If you plan to spend real time out there, insulating is a better investment than a bigger heater.
Electrical safety in an outbuilding
- A heater is a heavy, sustained load. Feed an outbuilding with a proper armoured supply and its own protection, installed by a qualified electrician — not a garden extension lead trailing from the kitchen.
- Sockets and the heater itself must stay dry, off the floor and clear of the roof.
- Keep the grille clear of sawdust, wood shavings, sacking and stored fabric, and vacuum it regularly.
- Never store or use flammable liquids or gas near an electric heater.
- Choose a unit with overheat and tip-over protection. Do not leave it unattended.
Timer strategies
For a garden office, start the heater half an hour before you walk out there and let it stop at the end of the day. For frost protection, low thermostat and leave it. Both approaches rely on decent controls — see thermostats and timers.
RapidHeat in a shed or workshop
Portable, thermostat-controlled and quick to reach temperature, RapidHeat suits an insulated shed or garden room used in sessions, and works as spot heating in a bigger workshop. It is a domestic room heater, so keep it dry, keep it clear of dust and shavings, and use it while you are present.
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
- What wattage heater do I need for a shed?
- For frost protection in a small, reasonably tight shed, 400–800 W on a thermostat is often enough. To work in comfort you are looking at 1,500 W or more, aimed at where you stand.
- How much does frost protection cost to run?
- A 500 W heater cycling on a low thermostat may only run a few hours a day in cold weather — often well under 50p a day at 27p per kWh.
- Is it safe to leave a heater in a workshop unattended?
- Only a unit with a thermostat and overheat protection, kept clear of sawdust, wood shavings, rags and solvents, on a proper fixed supply. Sweep up before you leave it running.
- Do I need special wiring for a shed heater?
- A shed should ideally have its own armoured supply and RCD protection fitted by an electrician. If you are running a lead from the house, use an uncoiled outdoor-rated lead and keep the load modest.
Keep the workshop dry and usable
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