Energy Saving Trust’s figure of about £12,000 for a typical air-source project is a national benchmark rather than a fixed quotation. A completed conversion may include a cylinder, radiators, pipework, controls, electrical upgrades and building work. The designer must also protect seasonal efficiency through appropriate heat loss, flow temperature and commissioning decisions; the outdoor unit price does not represent that full scope.
The outdoor unit is only one line in a whole heating-system project. A complete quotation may include survey, design, emitters, cylinder, controls, electrical work, condensate, base, pipe insulation, commissioning and removal of the old appliance.
Compare net cost after confirmed grant support, but retain the gross installed price. A proposal that looks cheap because it omits radiator or cylinder work may deliver poor comfort or create variations later.
Energy Saving Trust’s typical figure is a national anchor, not a cap. Ground-source work, difficult electrical upgrades and major emitter changes can cost more; simple modern homes can cost less. Confirm with the installer.
What changes the answer
Heat-loss survey
The design calculation determines equipment and emitter scope. Treat a quote produced before survey as provisional.
Emitter upgrades
Radiator size, underfloor zones and flow temperature affect both capital cost and future efficiency.
Hot-water provision
Cylinder replacement, cupboard alterations and immersion control should be explicit.
Electrical supply
The electrician must assess protective devices, cabling and available capacity.
External works
Bases, drainage, wall penetrations, pipe runs and access can change labour.
Commissioning
Balancing, weather compensation, handover and monitoring are part of a functioning installation.
Illustrative worked example
Illustrative example — an Oxford owner receives a gross quote matching Energy Saving Trust’s £12,000 typical cost. If eligible for the standard £7,500 BUS grant, the customer contribution is £12,000 − £7,500 = £4,500. If the property qualifies for Ofgem’s temporary £9,000 off-gas-grid level, the contribution is £3,000. These calculations do not include finance or later variations, and eligibility must be confirmed by the installer and Ofgem.
Rules and responsibilities for this topic
BUS process
For eligible England and Wales installations, the MCS-certified installer applies for the voucher and the property owner confirms consent.
Planning
Check permitted-development and noise conditions, particularly boundaries, flats, listed buildings and conservation areas.
Building services
Electrical, plumbing and structural work must comply with the relevant regulations and manufacturer instructions.
Price the whole heating conversion
Require a survey-based quotation that separates the heat pump, cylinder, emitters, pipework, electrical work, controls, groundwork, access and removal of old equipment. Ask which items remain provisional until floors are lifted or electrical capacity is checked. Two quotes can describe the same nominal unit yet differ greatly because one includes radiator upgrades and the other postpones them.
Use the room-by-room heat-loss calculation to judge whether enabling work is necessary. A cheaper design that relies on high flow temperatures can produce a worse long-term result than a properly sized system. Review cylinder location, condensate drainage, external clearances and cable routes before agreeing to the contract. If planning, network work or asbestos investigation may be needed, identify the responsible party and cost before installation begins.
Show grants as a separate deduction from the gross contract price and confirm eligibility through the official administrator. Add finance charges when comparing with a cash quotation. Request payment stages tied to survey, equipment delivery, commissioning and handover rather than sales milestones. The final pack should contain design temperatures, emitter schedule, electrical certificates, controls guidance and warranty registration. Use the quote checker to compare scope line by line; a complete higher quotation may be safer than an incomplete low one.
Ask each bidder to distinguish fixed prices from allowances. Ground loops, long cable routes, drainage, structural bases and concealed pipework can carry uncertainty that a survey cannot entirely remove. The contract should explain how variations are approved, evidenced and priced before extra work proceeds. Also establish whether decorating, floor repairs, temporary heating or waste removal are included. These items may not affect technical performance, yet they determine the household’s real budget and make supposedly similar quotations diverge after work starts.
Reconcile the final invoice with the survey
Before the balance is due, compare installed models, radiator schedule, cylinder, controls and electrical work with the accepted quotation. Record agreed variations separately and reject unexplained substitutions. Commissioning should demonstrate heat delivery, hot water, weather compensation and backup settings; certificates and warranty registrations are part of completion rather than optional paperwork. If grant support is involved, check that the invoice shows the gross price and deduction clearly. This reconciliation makes the real installation cost auditable and gives future service engineers an accurate system record.
Keep contingency visible rather than hiding it in a rounded total. A defined allowance for uncertain pipe routes or groundwork can be reconciled against evidence, while an unexplained margin cannot. The contract should say whether unused contingency is returned and require approval before it is exceeded.
Questions to ask the installer
- Is the price fixed after the heat-loss survey?
- Which radiators and pipe sections are included?
- Does the quote include a new cylinder and controls?
- What BUS amount and eligibility have you assumed?
- Which electrical or groundwork items are excluded?
- Who returns to optimise settings after commissioning?
Frequently asked questions
How much does an air-source heat pump cost?
Energy Saving Trust’s current typical installation figure is around £12,000. The actual gross price depends on the building, emitters, cylinder, electrical work and access. Compare itemised designs and show grants separately from the installation price.
Does the £7,500 BUS grant reduce the quote?
The grant is applied through the installer for an eligible installation and reduces what the property owner pays. Ofgem’s current rules also show temporary £9,000 support for certain eligible off-gas-grid properties until 31 March 2027. Confirm eligibility before committing.
Are radiator upgrades included?
Only if the quotation says so. A proper design identifies each emitter and its required output at the proposed flow temperature. Vague allowances can become expensive variations or encourage the system to run hotter and less efficiently.
Why are ground-source systems more expensive?
They require ground collectors, boreholes or trenches as well as indoor equipment and design work. Site access, geology and land area strongly affect cost. Obtain a property-specific survey and do not apply an air-source comparison price to ground-source work.
Should I choose the cheapest heat-pump quote?
Choose the strongest complete design at a justified price. A cheap unit with undersized radiators, missing electrical work or no commissioning support can cost more to correct and may run inefficiently. Compare heat loss, flow temperature, scope, warranties and aftercare.
Independent sources
- Energy Saving Trust, Air source heat pumps (accessed 3 October 2026)
- Ofgem, Boiler Upgrade Scheme (accessed 3 October 2026)
- Ofgem, Price-cap unit rates (accessed 3 October 2026)
- MCS, Standards and tools library (accessed 3 October 2026)
Last updated .