Garden Room and Garden Office Heating

Garden rooms and garden offices have taken off around Milton Keynes and the villages, and most owners run into the same issue in their first winter. The room is lovely from April to October. From November it's cold, it takes forever to warm with an oil-filled radiator, and it's damp by the time you give up and head back into the house.

A small Haier heat pump is the most common fix we fit. It's quick to heat, cheap to run and doesn't need anything plumbed in. Unlike a panel heater, it also cools the room when a south-facing garden room turns into a greenhouse in July.

Why garden rooms are harder to heat than they look

A garden room loses heat from every side: four outside walls, a roof and a floor, often with large glazed doors. A room in the house has neighbours on some sides, so it doesn't lose as much. That's why a 2kW heater that would be fine in a bedroom struggles in a garden room of the same size. We size for that. A well-insulated garden office of around 3m × 4m often suits a 2.5kW unit, and larger or more heavily glazed rooms need 3.5kW or 5.0kW.

How the installation works

• Outdoor unit: usually mounted on the garden room itself, on a wall bracket or on the ground beside it. That keeps the pipe run between the two units very short.
• Indoor unit: high on an internal wall, positioned so warm air doesn't blow straight at the desk or sofa.
• Power: the unit needs a proper supply. Most garden rooms already have an armoured cable from the house. We check it can carry the load at survey, and any electrical work is done to Part P standard.
• Condensate: in heating mode the outdoor unit produces water as it defrosts. We plan where that drains so it doesn't pool against the building.

Running costs versus a panel heater

At the Ofgem cap of 26.32p per kWh (October–December 2026), a 3.5kW heat pump at full heating output costs about 25.6p an hour. A 2kW panel or oil-filled heater costs 52.6p an hour and puts out less heat. If you use the room as an office every weekday, that difference adds up quickly. It also means you can keep the room from getting damp overnight for very little.

Keeping it dry, not just warm

Damp and condensation are common complaints in garden buildings over winter, especially ones that sit empty for days at a time. Keeping the room gently warm helps. In summer, the unit's cooling and dry modes take moisture out of the air.

Planning ahead? Tell your garden room builder

If your garden room is being built now, it's much neater to plan the heat pump in from the start. The pipe entry, the outdoor unit position and a suitable power supply can all be built in, rather than retrofitted. We're happy to talk to your builder directly.

Haier systems, certified installers

We install Haier exclusively. Keeping to one brand means our engineers know the range inside out, we hold the right spares, and costs stay down. Haier systems come with a 6-year warranty as standard when installed by a certified engineer. Our engineers are F-Gas certified, the business is REFCOM registered, and electrical work is carried out to Part P standard. We're based in Buckingham, MK18, and cover Milton Keynes, Buckinghamshire, Northamptonshire and the surrounding area.

Heat pump installers near you

Milton Keynes Buckingham Bletchley Newport Pagnell Aylesbury Bicester Northampton Oxford

See the full list of areas we cover, or check recent installations for real examples of our work.

More heating guides

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Common questions

What is the best way to heat a garden room?

For a garden room used regularly, a small air to air heat pump is usually the most cost-effective option. It heats quickly, costs far less to run than a panel or oil-filled heater, and also cools the room in summer.

What size heat pump does a garden office need?

A well-insulated garden office of around 3m by 4m often suits a 2.5kW unit. Larger rooms, or rooms with big glazed doors, typically need 3.5kW or 5.0kW. We confirm sizing at survey.

Where does the outdoor unit go?

Usually on the garden room itself, either wall-mounted or on the ground beside it, which keeps the pipe run very short.

Does my garden room need a new electrical supply?

Not always. Many garden rooms already have a suitable armoured cable from the house. We check the existing supply at survey and any electrical work is carried out to Part P standard.

Can a heat pump stop my garden room getting damp?

Keeping the room gently heated through winter helps prevent the cold surfaces that cause condensation, and the unit's dry mode removes moisture in warmer weather.