Heat pump advice
Air source heat pumps: is your home ready for one?
An air source heat pump can heat most homes, and a £7,500 grant now covers a large share of the cost. How well one works for you depends on the heat your home loses, the radiators it has and the tariff you run it on. Here is what the evidence says, from an assessor who does not sell them.
- Grant
- £7,500 through the Boiler Upgrade Scheme
- Typical installed cost
- Around £12,000 before the grant
- Efficiency
- Up to 3 to 4 units of heat per unit of electricity
- Installer
- Must be MCS certified
- Planning
- Usually permitted development
Reviewed October 2026
How an air source heat pump works
A heat pump does not make heat by burning fuel. It moves heat that is already in the outside air into your home. A fan draws air across a coil containing refrigerant, a compressor raises the refrigerant's temperature, and the heat passes into the water that feeds your radiators, underfloor heating and hot water cylinder.
Because it moves heat instead of generating it, a heat pump delivers more energy than it uses. The Energy Saving Trust says it can deliver three to four units of heat for each unit of electricity. You will see this written as a coefficient of performance, or CoP. The figure that matters over a year is the seasonal one, called SCoP or SPF, which your installer has to calculate for your home. The Energy Saving Trust puts a typical seasonal figure at about 3.1.
Is your home suitable?
Probably. The Energy Saving Trust says air source heat pumps suit most types of home, and that plenty of old and historic houses have had them fitted. What changes from home to home is how the system has to be designed.
- Heat loss. The more heat the building loses, the larger the heat pump and the radiators it needs. A home does not have to be fully insulated first, but insulating where it is cheap to do so makes everything that follows smaller and cheaper to run.
- Radiators. A heat pump runs at a lower water temperature than a boiler, so some radiators may need to be larger. Changing them is not compulsory, and a good installer will tell you which would benefit.
- Hot water. A standard air source heat pump does not heat water on demand as a combi boiler does. You need space for a hot water cylinder.
- The outdoor unit. It needs a place outside with air moving freely around it, positioned with your neighbours in mind.
What we look at on a survey
Walls, roof, floors and windows, element by element. The heating you have now and how it is controlled. Where a cylinder could go. How the home is ventilated, and any damp. That tells you how well the building holds heat and what would be worth improving first. Your installer then carries out the detailed heat loss design.
What it costs, and the grant
The Energy Saving Trust puts the typical cost of installing an air source heat pump at around £12,000. The figure for your home depends on the size of the heat pump, the size of the property and whether radiators need upgrading.
- Boiler Upgrade Scheme. £7,500 towards the cost in England and Wales, taken off the price by your installer. The heat pump must replace a fossil fuel or electric heating system, and hybrids that keep a gas boiler do not qualify.
- Homes on oil or LPG. Until March 2027 there is an extra £1,500 where the property has no mains gas connection.
- No VAT. Installation is zero-rated until 31 March 2027.
- Low-income households. The Warm Homes: Local Grant can fund a heat pump in full where the council has funding and the household qualifies.
Our guide to grants and schemes explains who can apply and how.
Running costs: the honest position
Electricity costs more than gas. Under Ofgem's price cap for October to December 2026, a unit of electricity averages 26.32p and a unit of gas 7.97p, so electricity is about 3.3 times the price. A heat pump makes up for that by delivering several units of heat for each unit of electricity. Whether it comes out ahead depends on how efficiently it runs in your home.
| Heating | Efficiency assumed | Cost of one unit of heat |
|---|---|---|
| Gas boiler | 90% | 8.9p |
| Heat pump, poorly matched to the home | 2.5 units of heat per unit of electricity | 10.5p |
| Heat pump, at the typical seasonal figure | 3.1 | 8.5p |
| Heat pump | 3.5 | 7.5p |
| Heat pump, well designed | 4.0 | 6.6p |
Our own arithmetic, using Ofgem's average unit rates for customers paying by direct debit between 1 October and 31 December 2026. The efficiencies are illustrations, not predictions for your home. Standing charges are left out.
One caution on those figures. Electricity carries no VAT from 1 October 2026 to 31 March 2027, while gas still carries 5%. With 5% VAT, a unit of electricity would cost about 27.6p, about 3.5 times the price of gas, and a heat pump would need to run at about 3.1 just to match a 90% efficient boiler on the cost of heat.
Two things move the result in a heat pump's favour. A tariff designed for heat pumps has cheaper periods during the day or night, and the Energy Saving Trust says that on such a tariff a heat pump can cost less to run than a gas boiler. And a home that stops using gas altogether no longer pays the gas standing charge, which is about £108 a year at the current cap.
What a heat pump does to your EPC
This surprises people. Today's EPC rating measures running cost, and because electricity costs more per unit than gas, replacing a gas boiler with a heat pump can leave the rating unchanged or even lower. Elmhurst Energy, one of our accreditation schemes, has said it often sees exactly that.
It is a quirk of the current method, and it is due to change. The reformed certificate planned for the second half of 2027 will show the heating system as a measure of its own, alongside the fabric of the building and its running cost. For landlords, the route to band C by 2030 is expected to be measured the same way, with fabric first.
If the rating matters to you, for a sale, a tenancy or a grant, ask us to model the change before you commit.
Planning permission and noise in England
Most air source heat pumps on a house are permitted development, so no planning application is needed if conditions including these are met.
- The outdoor unit is no larger than 1.5 cubic metres. For a block of flats the limit is 0.6 cubic metres.
- It is the only one on the property. A detached house may have two.
- The installation meets the MCS planning standard, which sets a noise limit at the neighbouring property.
- It is not on a pitched roof. On a flat roof it must be at least a metre from the edge.
- On a wall that faces a road, it is no higher than the ground floor.
- It is not used only for cooling.
Since 29 May 2025 the unit has no longer had to be at least a metre from the boundary. Listed buildings and scheduled monuments are excluded altogether. In a conservation area the unit cannot go on a wall or roof that faces a road, or closer to the road than the building. Councils can also remove these rights locally, so check with yours before work starts.
Choosing an installer
Your installer must be MCS certified for you to receive the grant. Ask each one for a room-by-room heat loss calculation, the seasonal efficiency they are designing for and a list of any radiators they would change. Keep the MCS certificate and the commissioning record when the job is done: they are your proof of what was fitted, and the evidence an assessor needs for your next EPC.
Other kinds of heat pump
- Ground source. Takes heat from pipes buried in the ground. It costs more to install and needs outdoor space. The grant is the same £7,500.
- Air-to-air. Heats, and can cool, rooms directly through wall units, and does not usually provide hot water. The Boiler Upgrade Scheme lists a £2,500 grant for homes. Ask your installer whether it can be claimed yet.
- Hybrid. A heat pump working alongside a boiler. There is no grant for a hybrid.
How Retrohaus helps
- Before: an EPC or a retrofit assessment that shows how well the home holds heat, and advice on what to improve first
- During: retrofit coordination where the work is funded and has to follow PAS 2035
- After: a new EPC, so that the heat pump is recorded on the public register
We also work with heat pump installers, providing the assessments and coordination that funded schemes require. See scheme and installer support.
Sources: Energy Saving Trust guides to air source heat pumps (updated 23 September 2026), heat pumps in depth (16 July 2026) and its heat pump fact check (1 July 2026); GOV.UK, Apply for the Boiler Upgrade Scheme; Ofgem, energy price cap for 1 October to 31 December 2026; HMRC VAT Notice 708/6; Planning Portal guidance on air source heat pumps and the Town and Country Planning (General Permitted Development) (England) (Amendment) Order 2025; Elmhurst Energy (September 2025); government response on reforms to the Energy Performance of Buildings regime (January 2026). This page is general guidance, not a recommendation for any particular property.
Heat pump questions
The questions we are asked most often.
How much is the heat pump grant?
£7,500 towards an air source or ground source heat pump, through the Boiler Upgrade Scheme in England and Wales. Until March 2027 there is an extra £1,500 for homes heated by oil or LPG that have no mains gas connection. The installer applies and takes the grant off your bill.
Do I need to insulate my home first?
Not necessarily. The Energy Saving Trust says a home can use a heat pump without being fully insulated, and recommends insulating first if you are able to. The less heat a home loses, the smaller the heat pump and radiators it needs and the less it costs to run.
Will a heat pump work in an old house?
Yes, if it is designed for the house. The Energy Saving Trust notes that plenty of old and historic homes have had heat pumps installed. Older homes lose more heat, so they often need larger radiators, and the installer has to size the system from a proper heat loss calculation.
Will a heat pump cost more to run than my gas boiler?
It depends on how efficiently it runs and on your tariff. Under the price cap for October to December 2026, while electricity carries no VAT, a unit of electricity costs a little over three times as much as a unit of gas, and the Energy Saving Trust says a heat pump can deliver three to four units of heat for each unit of electricity. The Energy Saving Trust says a heat pump can cost slightly more to run than a new gas boiler on a standard tariff, and less on a heat pump tariff.
Will my EPC rating go up?
Not always. The current rating is based on running cost, so swapping a gas boiler for a heat pump can leave it unchanged or lower, even though the home uses far less energy. The reformed certificate due in the second half of 2027 will show the heating system as a measure of its own.
Do I need planning permission for a heat pump?
In England most installations on a house are permitted development. The outdoor unit must be no larger than 1.5 cubic metres and the installation must meet the MCS planning standard, which includes a noise limit. Since May 2025 the unit has no longer had to be a metre from the boundary. Listed buildings are excluded, and conservation areas have extra limits.
Can a landlord get the grant?
Yes. The Boiler Upgrade Scheme is open to people who own the property, including landlords and the owners of second homes. Social housing is not eligible.