Heat Pump for Flats: The Air-to-Air Route
Efficient room heating without replacing every radiator—plus summer cooling. Compare the cost, grant rules, freeholder consent and realistic outdoor-unit options.
- Energy Saving Trust typical one-room cost: about £1,900
- £2,500 BUS route for eligible full-heating designs
- Lease consent and hot water still need a plan
Is an air-to-air heat pump for flats the right fit?
A conventional air-to-water heat pump normally needs room for an outdoor unit, a hot-water cylinder and a wet heating system designed for lower flow temperatures. Flats can make each part difficult. An air-to-air heat pump uses smaller refrigerant pipes and indoor fan units instead of feeding radiators. That can reduce internal disruption and make one-room or multi-room zoning much easier.
It is also the same underlying system as fixed reversible air conditioning. The flat gets useful winter heat, summer cooling and dehumidification from one installation. That year-round case is strongest in smaller electrically heated homes, top-floor flats that overheat, properties without a wet central-heating circuit and rooms where replacing storage or panel heaters is being considered.
It is not automatically the answer for every apartment. Indoor units need acceptable positions, the outdoor unit needs airflow and service access, and warm air does not reliably pass through closed doors. Most air-to-air systems do not produce domestic hot water. The survey has to solve the whole flat rather than simply find a wall for a unit.
Flat heat-pump options compared
| Option | Best fit | What the survey must solve |
|---|---|---|
| Single split | Studio, open-plan flat or one priority room | Whether heat reaches the intended occupied area and what heats other closed rooms |
| Multi-split | Two or more rooms with one permitted outdoor position | Pipe routes, simultaneous winter capacity and one-condenser resilience |
| Separate single splits | Larger flat with more than one acceptable outdoor position | External appearance, number limits, planning and freeholder response |
| Fixed monobloc | External box refused but discreet wall grilles may be allowed | Two façade penetrations, indoor compressor noise and winter performance |
| Ducted air-to-air | Newer flat or renovation with ceiling/service voids | Duct space, fire compartmentation, access, fan pressure and balanced room delivery |
| Air-to-water | Flat with suitable wet system, cylinder space and plant location | Whole-building constraints, emitter sizes, hot water and major internal works |
If the project is cooling-led rather than heating-led, compare the wider external, monobloc and water-cooled choices in our air conditioning for flats guide.
How much does a heat pump for a flat cost?
Energy Saving Trust currently cites about £1,900 for a one-room air-to-air heat pump. For early budgeting, a broader installed range of £1,400–£3,200 covers many straightforward single splits. A two-room or larger multi-split commonly lands around £3,000–£8,500, with the exact total driven by system capacity and the building constraints below.
| Flat project | Planning allowance | Common extras |
|---|---|---|
| One-room wall split | £1,400–£3,200 | Long pipework, condensate pump, electrical circuit, premium quiet unit |
| Two-room multi-split | £3,000–£5,500 | Concealment, multiple drains, difficult access and communal-area protection |
| Three-to-four-room system | £3,500–£8,500+ | Full heat-loss design, more indoor heads, electrical and access work |
| Fixed monobloc | £2,000–£4,000 per room | Large core holes, grilles, making good and acoustic treatment |
High-floor access, scaffold or lifting plans, restricted working hours, loading bookings, lift protection, asbestos information, fire stopping and freeholder technical-review fees can make a flat installation cost more than the same equipment in a house. A useful quote states who is paying and managing each item.
The £2,500 grant for qualifying flats
Current GOV.UK and Ofgem guidance includes a £2,500 Boiler Upgrade Scheme grant for eligible residential air-to-air heat pumps in England and Wales. Ofgem says the installer must hold MCS certification and applies on the owner’s behalf. The grant should be shown as an upfront reduction in the installation quote.
The proposed system must meet current technical and property rules. That includes replacing an existing fossil-fuel or electric heating system and being capable of meeting the property’s full space-heating needs. This matters in a flat: one head in the lounge may be a valuable heating upgrade, but it is not automatically a qualifying whole-flat design. Social housing and non-residential air-to-air projects are excluded under Ofgem’s current property rules.
GOV.UK Boiler Upgrade Scheme values, Ofgem property-owner rules and Energy Saving Trust air-to-air costs and suitability.
Planning permission and freeholder consent are different checks
Planning Portal guidance for England now says air-source heat pumps on a house or a block consisting wholly of flats can be permitted development when all conditions are met. For a block of flats, the outdoor compressor unit must not exceed 0.6 cubic metres; the installation must comply with MCS 020a; number, roof, elevation and protected-site limits apply; and the system must not be used solely for cooling. Local restrictions can remove permitted-development rights.
This does not grant permission under the lease. The freeholder or managing agent can still require a licence to alter, technical review, acoustic report, structural confirmation, fire-stopping details, contractor insurance and access arrangements. Obtain the property-specific planning and lease positions in writing before paying for equipment.
Scotland, Wales and Northern Ireland use their own planning frameworks. Even within England, listed buildings, scheduled monuments, conservation areas, mixed-use blocks and Article 4 restrictions need specific advice. Our UK planning guide is a starting point, not a substitute for the local authority or lease.
Outdoor unit, sound and drainage
A balcony is not automatically a suitable plant space. The condenser needs clear airflow and can recirculate its own cold discharge air in winter or hot discharge air in summer if recessed. The support must control vibration, remain safely maintainable and avoid blocking an escape route. The survey should assess neighbours’ bedroom windows and quiet night-time conditions, not only the flat’s own room.
Heating mode produces defrost water at the outdoor unit; cooling mode produces condensate indoors. Both need safe, approved drainage that cannot drip over balconies, freeze on a walkway or damage flats below. Ask for the route and failure response on the drawing.
Room coverage and hot water
A proper proposal starts with heat loss for each room. In a studio or open-plan flat, one well-positioned unit may cover most occupied space. In a two-bedroom flat with closed doors, each bedroom may need its own indoor head or another heat source. Oversizing one lounge unit does not solve distribution and can make temperature control worse.
Most air-to-air heat pumps leave tap and shower water to a separate system. The flat may retain a gas combi boiler for hot water, use a cylinder and immersion, have an electric shower or need another designed solution. Include that cost and space in the decision; “boiler replacement” is not a fair description if hot water has been left unanswered.
What to send the freeholder and installer
- Lease or alteration-policy requirements and written ownership details for the proposed plant area.
- Scaled indoor and outdoor positions, pipe routes, penetrations, drains and electrical supply.
- Model-specific heating output, SCOP, indoor sound and outdoor sound-power data.
- Heat-loss calculations for every room the proposal claims to heat.
- Structural fixings, vibration control, fire stopping and safe maintenance access.
- Planning assessment, F-Gas credentials and MCS/BUS confirmation if a grant is proposed.
- Hot-water and backup-heating plan, full cost, warranty and servicing requirements.
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Heat pumps for flats FAQs
Can you install a heat pump in a flat?
Yes. An air-to-air heat pump is often a practical fit because it heats room air without new radiators or wet pipework and can also cool in summer. The design still needs a compliant outdoor position or an appropriate internal alternative, freeholder approval where required, planning checks and a separate hot-water plan.
How much is an air-to-air heat pump for a flat?
Energy Saving Trust currently gives a typical figure of about £1,900 for one room. A broader market allowance for a professionally installed single split is around £1,400–£3,200; access, high floors, long pipe routes, electrical work, permissions and premium low-noise equipment can increase it. Multi-room flat systems commonly move into the £3,000–£8,500 range.
Can a flat get the £2,500 air-to-air heat-pump grant?
Eligible residential properties in England and Wales can use the Boiler Upgrade Scheme route under current GOV.UK and Ofgem guidance. An MCS-certified installer applies, and the system must meet current rules including replacing an existing fossil-fuel or electric heating system and meeting the full space-heating load. A cooling-only add-on does not satisfy that design intent.
Do I need freeholder permission for a heat pump in a flat?
Usually, if the proposal alters the exterior, common structure, services or shared areas. Planning status does not override the lease. Obtain written consent before ordering equipment and give the freeholder equipment positions, penetrations, sound data, drainage, fixings, fire-stopping and maintenance details.
Does permitted development cover heat pumps on blocks of flats?
Current Planning Portal guidance for England says an air-source heat pump on a block consisting wholly of flats can be permitted development when every condition is satisfied. Conditions include MCS 020a, a 0.6m³ outdoor-unit volume limit for blocks of flats, limits on the number and position of units, protected-site rules and not using the system solely for cooling. Local and lease restrictions can still require consent.
Will an air-to-air heat pump provide hot water in a flat?
Normally no. It heats indoor air directly. The design must retain or add a separate way to heat shower and tap water, such as an existing boiler, cylinder with immersion, electric shower or another properly designed system.
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