Garden office heaters: what to buy and what it costs to run
How to heat a garden office or garden room for less: the right size, the best heaters and what a working day costs at the Ofgem price cap.
What it costs to heat a garden office
A well-insulated garden room of about 10–12 m² usually needs a 1–1.5 kW heater. On a thermostat it heats perhaps half the time once the room is warm:
| Heater | Working day (8 h) | Month (21 days) |
|---|---|---|
| 1.5 kW panel or oil filled radiator, on thermostat | £1.58 | £33.16 |
| 1 kW panel heater, on thermostat | £1.05 | £22.11 |
| 55 W heated foot mat, all day | 11.6p | £2.43 |
Estimates at the Ofgem price cap (26.32p/kWh). A poorly insulated summerhouse will need more.
The best heaters for a garden office
- A panel heater with Wi-Fi or a weekly timer: it warms the office before you walk down the garden and stops when you finish.
- An oil filled radiator: silent, steady heat for video calls.
- A heated foot mat: on cold mornings, warm your feet while the room heats up.
Devola DVPW2500WH Smart Glass Panel Heater 2500W
- Panel heater · 2,500 W
- The 2.5 kW version of the Devola smart glass panel: Wi-Fi app and voice control, a thermostat accurate to about half a degree and a 7-day timer, for living rooms up to about 25–30 m².
- Costs 65.8p an hour at full power.
Russell Hobbs RHOFR5001 1500W 7 Fin Oil Filled Radiator
- Oil filled radiator · 1,500 W
- Best-selling budget oil radiator: 1.5 kW with three settings (600, 900 and 1,500 W) and an adjustable thermostat, for rooms up to 15 m².
- Costs 39.5p an hour at full power.
OLYDON Heated Floor Mat Under Desk 55W
- Under-desk heater · 55 W
- A 55 W heated mat to rest your feet on under the desk, with 7 temperature settings and a 3-hour auto-off: a full working day costs a few pence.
- Costs 1.4p an hour at full power.
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Before you plug in
- A garden office should have its own properly installed supply (usually an armoured cable fitted by a qualified electrician), not an extension lead from the house.
- Use the frost setting if you keep electronics in it over winter, and a small dehumidifier if you get condensation.
Frequently asked questions
What size heater do I need for a garden office?
About 100 W per m² if it is well insulated: 1–1.5 kW for 10–15 m². Poorly insulated summerhouses need more, and lose it faster.
What is the cheapest way to heat a garden office?
Insulate it, then use a panel heater or oil filled radiator on a thermostat and timer, about £1.58 a working day for 1.5 kW. Add a heated foot mat (1.4p an hour) on cold mornings.
Can I leave a heater on in a garden office overnight?
Use the frost setting rather than heating it overnight. Only use heaters designed for long periods, on a proper fixed supply.
Running costs use the Ofgem energy price cap, 1 October to 31 December 2026: average unit rate for electricity paid by Direct Debit (26.32p/kWh, standing charge 54.83p/day) and gas (7.97p/kWh). National averages; your region and tariff may differ. Prices on Amazon change: check the live price before you buy.