Garden room running cost calculator

By the Garden Room Guide Team · Updated

Filled in with a typical 12 m² garden office used on working days. Change anything and the costs update.

1. Heating

Rule of thumb: about 0.1 kW per m² for a well-insulated room.

2. Insulation

How much of the time the heater runs at full power to hold the temperature.

3. How you use it
4. Electricity price

The Irish average was 36.06c per kWh in September 2026.

See breakdown

Heating and power over a year

An estimate using simple assumptions: heater power × hours × how much of the time it runs, divided by efficiency. Real costs depend on the weather, your thermostat and your tariff.

Sources

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