Air source heat pump: costs, suitability and choosing an installer

A guide to commissioning an air source heat pump: suitability checks, permissions, hiring order, realistic costs and avoiding bad installers.

ASHP-01What the job actually involvesAn air source heat pump sits outside and extracts heat from the air to warm your home and hot water, usually replacing a gas boiler. It needs a well-insulated house, larger radiators or underfloor heating in many cases, and sometimes a new hot water cylinder. This is a whole-system change, not a boiler swap, so the work touches heating, electrics and sometimes the fabric of the house.

ASHP-02Start with a heat loss survey, not a quoteBefore anyone talks price, you need a proper room-by-room heat loss survey. This tells you the right size of heat pump and whether your radiators or pipework need upgrading. A survey done properly (not a 20-minute guess) is the single biggest factor in whether the system actually keeps you warm.

ASHP-03Check planning permission before booking an installerMost domestic air source heat pumps count as permitted development in England and don't need planning permission, provided the outdoor unit meets size and position rules. Listed buildings, some positions in conservation areas, and new-build estates with planning conditions can need permission. If you live in a flat, you’ll also need the freeholder’s agreement. Check the Planning Portal and your council before committing to a position for the unit.

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Planning permission may be required depending on property type, location and the unit's position — check with your local planning authority before installation.

ASHP-04Hiring order: surveyor, then installer, then electrician if neededFirst get an independent or installer-led heat loss survey. Then get quotes from MCS-certified installers, who will design the system around that survey. Only after the installer confirms the electrical load should you need a separate electrician — most installers handle this themselves, but an older fuse board or limited supply capacity may need upgrading first.

ASHP-05Building Regulations and electrical safetyInstalling a heat pump and any related electrical work must comply with Building Regulations, including Part P electrical safety rules. Using an MCS-certified installer registered with a Competent Person Scheme means they self-certify the work and notify Building Control for you — no separate application needed. If you use a non-certified installer, you must notify Building Control yourself and pay a fee.

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Heat pump and associated electrical work fall under Building Regulations and Part P. MCS-certified installers notify Building Control automatically via their Competent Person Scheme.

ASHP-06Realistic costs for 2026For an average three-bedroom house outside London, expect roughly £10,000 to £15,000 for a full air source heat pump installation before any grant, including the unit, a new hot water cylinder and some radiator upgrades. Costs rise towards the top of that range for larger properties, poor existing insulation, a full set of new radiators, or awkward access for the outdoor unit. London and the South East typically run higher.

ASHP-07Government grant: check the current amountIn England and Wales, the Boiler Upgrade Scheme currently gives £7,500 towards an air source heat pump, and until March 2027 an extra £1,500 if your home is heated by oil or LPG with no mains gas. The grant comes off the price you pay. Your installer applies for it, and they must be MCS-certified to do so. Amounts and rules change, so check GOV.UK before you budget. Scotland and Northern Ireland have different schemes.

ASHP-08TimescalesFrom initial survey to a working system usually takes 6 to 12 weeks, depending on installer availability and whether electrical upgrades are needed. The physical installation itself typically takes 2 to 4 days. Delays usually come from waiting lists for popular MCS installers, not the install itself.

ASHP-09What a good quote must containA proper quote should show the heat pump model and output size, a room-by-room heat loss calculation, which radiators are being changed or kept, cylinder size, the exact position of the outdoor unit, and whether MCS certification and grant handling are included. It should also state the warranty length on the unit and the installation guarantee. If a quote is just a single total figure with no breakdown, treat that as a warning sign.

ASHP-10Questions to ask and red flagsAsk to see their MCS certification number, ask for two recent heat pump references (not boiler ones), and ask what happens if the heat loss survey later shows a bigger unit is needed. Red flags: pressure to sign same-day, no written heat loss calculation, a quote based on a phone call alone, or refusal to confirm MCS status in writing. Avoid any installer who can't explain clearly how the grant application works.

ASHP-11What commonly goes wrongThe most common complaint is a system that runs expensively or doesn't keep the house warm, almost always because the heat loss survey was rushed or skipped. The second is disputes over the outdoor unit's noise or position with neighbours, which a proper survey and siting discussion avoids. A third is installers who promise grant money without confirming eligibility first, leaving the homeowner short when the application is refused.

ASHP-12If you live in Wales, Scotland or Northern IrelandIn Wales, the process and Boiler Upgrade Scheme eligibility are broadly similar to England, but check Welsh planning rules for permitted development separately. In Scotland, ask your council's building standards team whether your installation needs a building warrant; the Boiler Upgrade Scheme doesn't apply, but Scotland has its own grants and loans. In Northern Ireland, building control and grant schemes differ again, so check with your local council and nidirect before booking any work.

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Scotland's building standards and grants differ from England's, so check locally. Northern Ireland has its own building control and grant system.

ASHP-13Final sign-off before paying the last instalmentBefore releasing final payment, get the MCS certificate, the Building Control confirmation (automatic if MCS-registered), the manufacturer's warranty registration, and a written handover explaining how to use the controls. Keep all paperwork — you'll need it if you sell the house or claim under warranty later.

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You should receive an MCS certificate and Building Control compliance confirmation before the job is considered legally complete.

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Before you start: Which electrical jobs can I do myself? Part P explained

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