Heat Pumps for Flats

Estimate the Saving for Your Flat

The calculator compares a heat pump with gas, oil, LPG or single-rate electric heaters. If you have storage heaters on Economy 7, the running costs further down compare those too.

Heat Pumps in Flats: It's Complicated, But Not Impossible

An air-to-water heat pump, the kind the £7,500 grant pays towards, has an outdoor unit that goes on a wall or on the ground, with some space around it for air. In a flat, every one of those places is outside your own front door, so it involves the building and not just your home.

It also needs somewhere for hot water. A standard air source heat pump doesn't give you hot water on demand the way a combi does, and the Energy Saving Trust says a cylinder can usually fit in a cupboard of at least 80cm by 80cm.

What works in your favour is how little heat a flat uses. DESNZ's National Energy Efficiency Data-Framework puts the median gas use of flats in England and Wales at 5,922 kWh a year, weather corrected, for mid-May 2024 to mid-May 2025. It's 5,704 kWh for purpose-built flats and 7,141 kWh for converted ones. That's all the gas, cooking and hot water included.

Through a 90% boiler it's about 5,300 kWh of heat a year, a little high because some of that gas goes on cooking. It's our estimate for a typical flat and the figure the calculator above starts from.

The Three Main Challenges

1. Freeholder Permission

Most flats are leasehold: you own the flat for a fixed number of years, set by your lease, which is your agreement with the landlord (sometimes called the freeholder). The lease tells you what you've agreed to, including whether you need permission to make alterations. gov.uk warns that if you don't follow the conditions of the lease you could be taken to court and made to pay for any damage, and the court may take away your lease.

Planning and the lease are separate. Permitted development means you don't need a planning application; it doesn't give you the freeholder's consent, and the freeholder's consent doesn't give you planning permission. We'd get the consent in writing, with where the outdoor unit and pipes will go, before paying any deposit.

Scotland works differently. A flat there is part of a tenement, which mygov.scot says includes modern apartment blocks, and the roof and external walls are common areas. Your title deeds set out the owners' responsibilities for those common areas and how decisions about them are made, so read those instead of a lease.

2. Where Does the Outdoor Unit Go?

In England a heat pump on a block of flats is permitted development, so no planning application, if:

• It's the only one. No more than one air source heat pump on, or within the grounds of, the whole block.
• Size. The outdoor unit, including any housing, is no bigger than 0.6 cubic metres (on a house it's 1.5).
• Roofs. It isn't on a pitched roof, and on a flat roof it's at least 1 metre from the edge.
• The front. Outside a conservation area or World Heritage Site it can go on a wall that faces the road, but only at ground floor level. In one, it can't go on a wall or roof facing the road at all, or anywhere closer to the road than the block.
• Not listed. A listed building gets no permitted development for a heat pump, and nor does a scheduled monument.
• No wind turbine. There isn't one on the block or in its grounds.
• Noise. It meets the MCS 020 a) noise standard (next section), and it's sited, so far as practicable, to keep its effect on the look of the building and the area to a minimum.

In practice that means a ground-floor garden or terrace, a back wall, a balcony with room around the unit for air, or a flat roof. Ask the installer where the pipes would run to your flat before you ask the freeholder, because the consent should cover both.

The rules only cover a "block of flats", which the law defines as a building made up wholly of flats. A house is covered by the house rules, but in England a flat in a building that isn't all flats, such as one above a shop, is neither, so it needs a planning application.

Wales has had the same one-per-block rule since 1 June 2026, with a limit of 1 cubic metre on a block of flats. In Scotland, permitted development covers a heat pump on a flat too, but only one on the same building. It can't stick out more than 1 metre from the wall or roof, and it has to meet the older MCS 020 standard. In a conservation area there, it has to be at ground floor level on the back of the building. In Northern Ireland, ask your council.

3. Noise in Close Proximity

For permitted development in England the heat pump has to come in at or under 37 dB at the assessment position: 1 metre outside the middle of a neighbour's nearest door or window to a habitable room, worked out with the MCS 020 a) method. On a block of flats, MCS 020 a) counts every other flat in the block as a neighbouring property, so the window that matters may be beside, above or below the unit.

Each hard surface close to the unit (the wall behind it, a wall alongside) raises the figure, because sound reflects off it, and a solid wall or fence between the unit and the window brings it down. The calculation starts from the unit's sound power level, not its low noise mode figure. Run it for each neighbouring window here:

Air-to-Air Units: A Partial Solution

The Energy Saving Trust says air-to-air heat pumps are more often used in smaller homes such as flats and park homes. Their outdoor units are typically smaller than an air-to-water heat pump's, and there are all-in-one units with no outdoor unit at all, which reach the outside air through two small ducts in an outside wall.

It's a partial solution because most air-to-air systems don't provide hot water, so you'd need something else for hot water, such as a cylinder with an immersion heater or an electric shower. The Boiler Upgrade Scheme lists £2,500 towards one, in homes only, and the heat pump has to be able to meet all of the home's space heating on its own. Nobody can claim it yet, though: in September 2026 MCS said no installers were certified for air-to-air.

The catch: DESNZ's statistics show 145 air-to-air voucher applications and none issued between 28 April 2026 and the end of August 2026. In September 2026 MCS said the certification bodies were still working towards UKAS accreditation to certify air-to-air installers, and only a certified installer can claim the grant for you. In Scotland, Home Energy Scotland doesn't fund air-to-air heat pumps.

An air-to-air unit used for heating is a heat pump too, so if it has an outdoor unit, check with your council whether it fits the permitted development rules above. Our air-to-air guide covers the rest.

If your flat can take an air-to-water heat pump (the freeholder agrees, there's a spot for the outdoor unit and a cupboard), we think it's the better buy, because it does your hot water and the grant is being paid. If it can't, air-to-air is the realistic option, but we wouldn't count on the grant until MCS can certify installers for it.

Communal Heat Pump Systems

If your block has communal heating, with heat and hot water coming from a central plant, that's a heat network. Ofgem regulates heat networks in Great Britain, and Citizens Advice, Consumer Scotland and the Energy Ombudsman now give heat network customers advice and handle complaints.

Changing a communal system to a heat pump is a decision for whoever runs the building, not for one flat, so we'd raise it with your managing agent or residents' association.

Ground Source Loop Sharing

A block can share a ground loop. The Energy Saving Trust says this is usually done by installing the heat pump and pipework to the whole building at once, with maintenance built into the service charge. The Boiler Upgrade Scheme gives £7,500 towards a ground source heat pump. On a shared ground loop each flat makes its own voucher application, with consent from each flat's owner. It's rare so far: DESNZ's statistics show 46 vouchers issued for shared ground loop heat pumps by the end of August 2026, against 122,699 for air-to-water.

We think a shared ground loop is only realistic as a whole-block project the managing agent or freeholder leads. It isn't something one leaseholder can drive.

When a Flat Genuinely Isn't Suitable

Any of these can stop a heat pump for your flat, or at least make it a lot harder:

• Your lease needs consent and the freeholder says no. Then it's a conversation, not an install.
• The building is listed, so there's no permitted development.
• Your flat is above a shop or in another building that isn't all flats: in England you'll need a planning application.
• Someone in the block already has a heat pump, so yours needs a planning application.
• You're in shared ownership or social housing. Neither can get the Boiler Upgrade Scheme grant. For social homes it's your landlord's decision, and the Warm Homes Plan sends government money for them through the Warm Homes: Social Housing Fund for now.
• There's no cupboard of about 80cm by 80cm for a cylinder or a compact heat pump. Then the Energy Saving Trust's other suggestion, an air-to-air heat pump, is the one left.

When a Flat Can Work Well

On the other side, a flat can be a straightforward heat pump job when:

• the freeholder agrees in writing, or you own the freehold
• there's a spot for the outdoor unit that passes the noise rule at your neighbours' windows, and no one else in the block has used the permitted development allowance
• there's a cupboard of about 80cm by 80cm for a cylinder
• you're replacing storage heaters, where the running cost saving below is far bigger than against gas

Costs for Flat Installations

Air-to-water costs are the DESNZ medians for the two smallest sizes (Boiler Upgrade Scheme statistics, 2025/26 installs by capacity). A small heat pump doesn't cost much less than the typical one: the median across all sizes was £13,021. Air-to-air costs are the Energy Saving Trust's.

The grant rules that catch flat owners out

• You must own the property. Ofgem asks the owner to confirm their ownership, or their authority to act for all the owners. If you own it jointly, one of you gives consent for both.
• Shared ownership is out. Ofgem counts it as social housing, which can't get the grant. Most new builds can't either.
• Electric heating counts. gov.uk lists oil, gas, electric or LPG as the heating you can be replacing. Ofgem's guidance leaves existing heat pumps out of the electric heating it's aimed at.
• No EPC or insulation condition. Both were dropped, so an installer who says you need either is out of date.
• Get the consent first. Once a voucher is issued for an air source heat pump it expires after 3 months, which isn't long if you're still waiting on the freeholder.
• England and Wales only. In Scotland, Home Energy Scotland offers a grant of up to £7,500 for a heat pump (£1,500 more for rural and island homes), plus an optional interest-free loan. In Northern Ireland, the Energy Saving Trust says there isn't a specific heat pump grant, but NISEP's Green Heat NI and Toasty Homes schemes fully fund an air source heat pump for owner-occupiers with a household income under £28,000 (single) or £35,000 (couple or family) replacing old or no heating (our Northern Ireland heat pump grants page).

Running Costs

At the 1 October to 31 December 2026 cap (26.32p a kWh for electricity, 7.97p for gas), on our 5,300 kWh of heat a year:

• 90% gas boiler: about £470 a year
• Storage heaters on Economy 7: about £1,000 a year, if 75% comes in at the night rate (14.19p) and the rest at the day rate (32.65p). The 75% is our assumption; the rates are Octopus's Economy 7 tariff averaged across its regions on 23 October 2026
• Air-to-water heat pump, standard tariff: about £400 a year, at a SCOP of 3.5
• Air-to-water heat pump, heat pump tariff: about £300 a year, at our estimate of a 20p blended rate
• Air-to-air heat pump, A++ label: about £300 a year on a standard tariff, at the A++ minimum SCOP of 4.6, if it did all of that heat. Most can't do hot water, and hot water from an immersion heater costs the full electricity rate, so the real figure is higher

Those are fuel costs only, without standing charges. Against gas, a heat pump saves about £70 a year on a standard tariff, which won't pay back the install on its own. Against storage heaters it saves about £600 a year.

If you have the gas supply disconnected altogether, you also stop paying about £108 a year of gas standing charge, though you'd then cook on electricity, which none of these figures count. The savings calculator above counts that standing charge in your gas bill and starts with a heat pump tariff switched on, so its saving is bigger than these. Our storage heater guide works through that comparison in detail.

What to Do Next

1. Read your lease for what it says about alterations, and ask the freeholder or managing agent in writing. In Scotland, read your title deeds for how the owners decide on common areas.
2. Check the building: is it listed, in a conservation area, all flats, and does anyone else in the block already have a heat pump?
3. Find the two spaces: a spot for the outdoor unit and a cupboard for the cylinder, or decide on air-to-air.
4. Get quotes from MCS certified installers, and ask each one for the heat loss calculation and their MCS 020 a) noise result at your neighbours' windows.

More: Heat pump noise and the 37 dB rule | How the £7,500 heat pump grant works | Heat pumps in terraced houses