Annexe Heating: Independent Warmth for a Granny Annexe

Annexes, whether a converted outbuilding, a garden annexe or a self-contained part of the main house, have their own heating needs. Whoever lives there wants to control their own warmth without relying on the main house's boiler timer. Family often want the reassurance of being able to check the temperature from their phone.

Why heat pumps suit annexes

• Independent of the main house. The annexe has its own system and its own thermostat, and doesn't depend on the main boiler.
• Simple to use. A handheld remote with a big temperature display. Set it once and it holds that temperature.
• App control for family. Haier's Wi-Fi control means family members can check the temperature or adjust it from their phone if they need to.
• Quick heat. Warm air in minutes on a cold morning, rather than waiting for storage heaters or radiators.
• Cooling in heatwaves. Small annexes, particularly timber garden annexes, can get very warm in summer. Being able to keep the space cool matters for comfort, especially for older relatives.

One room or the whole annexe

A studio-style annexe usually needs a single split system. An annexe with a separate living room and bedroom suits a multi-split with one indoor unit in each room, each with its own control, all from one outdoor unit.

Power and practicalities

Many annexes have their own consumer unit, and some have a separate meter. We check the supply at survey, and all electrical work is done to Part P standard. For garden annexes, the outdoor unit is normally mounted on or beside the annexe itself to keep the pipe run short. See garden room heating for more on outbuildings.

Running costs

At the October–December 2026 cap of 26.32p per kWh, a heat pump delivers heat for about 7.3p per kWh, against 26.3p for plug-in or panel heaters. If the annexe has its own meter, that difference shows up directly on its bill.

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.

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Common questions

What is the best heating for a granny annexe?

An air to air heat pump is a good fit. It is independent of the main house, simple to control with a remote, heats quickly, can be checked by family through a phone app, and cools the annexe in hot weather.

Can family control the annexe heating remotely?

Yes. Haier units include Wi-Fi app control, so the temperature can be checked or adjusted from a phone.

Does the annexe need its own electrical supply?

Not necessarily, but many have their own consumer unit. We check the existing supply at survey and any electrical work is carried out to Part P standard.

Can one system heat a two-room annexe?

Yes. A multi-split system runs an indoor unit in each room from a single outdoor unit, each with its own control.

How much does it cost to heat an annexe with a heat pump?

Heat from a Haier heat pump costs about 7.3p per kWh at the October to December 2026 price cap, compared with about 26.3p per kWh for plug-in or panel heaters.