Heating a garden room: options and running costs
The short answer
Most garden rooms are heated with electric panel heaters (cheap to buy) or an air-to-air heat pump (cheaper to run, and it cools in summer). A well-insulated 12 m² room typically needs about 1 to 1.5 kW of heat. At around 36c per kWh, insulation and a timer make a bigger difference to running costs than the heater you choose.
Heating options compared
| Option | Good for | Watch out for |
|---|---|---|
| Electric panel or oil-filled heater | Low cost to buy, no installation beyond a socket | Higher running costs |
| Infrared panel | Quick warmth where you sit, slim wall or ceiling panels | Less even heat in a draughty room |
| Electric underfloor heating | Even, invisible heat; warm floor | Fitted during the build; slower to warm up |
| Air-to-air heat pump | Lowest running cost; also cools in summer | Highest upfront cost; outdoor unit needed |
Supplier heating packages typically cost €1,000 to €5,000, depending on the system.
What size heater
As a rough rule, a well-insulated garden room needs about 100 watts per m². A poorly insulated room needs more.
| Room size | Heater, well insulated |
|---|---|
| 9 m² | About 1 kW |
| 12 m² | 1 to 1.5 kW |
| 16 m² | About 1.5 to 2 kW |
| 25 m² | About 2.5 kW |
This is a rule of thumb, not a heat loss calculation. Large glazing, a north-facing room or poor insulation all push it up.
Running costs
The average Irish electricity price was 36.06c per kWh in September 2026. A heater only draws full power while it's heating, so a thermostat cuts the real cost.
| Example | Cost per working day |
|---|---|
| 2 kW panel heater, on half of an 8-hour day | About €2.90 |
| Same heat from a heat pump (about 3 times as efficient) | About €1 |
| Laptop, monitor and lighting for 8 hours | About €0.40 |
Work out your own running costs
Enter your room size, heater, hours and electricity price to see the cost per day, month and winter.
Keeping costs down
- Insulate properly first. It's the biggest saving. See insulated garden rooms.
- Use a thermostat and timer, so the room warms up just before you start.
- Keep a low background heat in deep winter rather than heating from cold. It also prevents condensation.
- Seal draughts around doors and windows.
Common questions
What is the cheapest way to heat a garden room?
In a well-insulated room, an air-to-air heat pump is usually cheapest to run, because it delivers several units of heat for each unit of electricity. Electric panel heaters are cheapest to buy but cost more to run.
How much does it cost to heat a garden room in Ireland?
It depends on size, insulation and how often you use it. With electricity at around 36c per kWh, a 2 kW heater running for half of an 8-hour day costs about €2.90 a day. Use our running cost calculator for your own figures.
Can I put a wood-burning stove in a garden room?
It's possible, but it needs a proper flue, fire-safe clearances and hearth, and an air supply. Check with the supplier and a qualified installer. For most small rooms, electric heating is simpler and safer.
Sources
Garden room companies serving Dublin
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