Heat pumps

An air-source heat pump absorbs heat from outside air. A ground-source system collects heat through buried pipework. Refrigerant and a compressor raise the temperature so the heat can be delivered to radiators, underfloor heating or warm-air units.

Air-to-water heat pumps are the most common whole-home systems in the UK. They heat water for a wet central-heating system and normally use a cylinder for domestic hot water. Air-to-air systems blow warm or cool air into rooms and do not usually provide hot water. Ground- and water-source systems can be efficient but require suitable land, boreholes or access to a water source and generally cost more to install.

Most types of home can use a heat pump, but the design needs to match the property. An installer should assess:

• room-by-room heat loss;
• insulation and draughts;
• existing radiators, underfloor heating and pipework;
• required indoor temperatures and occupancy patterns;
• hot-water use and cylinder space;
• a suitable outdoor-unit location;
• noise and planning constraints;
• the electrical supply and consumer unit; and
• access for installation and maintenance.

Insulation is not an absolute requirement for every home, but reducing unnecessary heat loss can allow a smaller system and lower flow temperature. It may also improve comfort whichever heating system is chosen.

Ask to see the heat-loss calculation and proposed design temperature. A quotation based only on floor area or the rating of the old boiler is not enough.

A gas or oil boiler can send very hot water through radiators for short periods. A heat pump normally performs better when circulating cooler water for longer. To deliver the same room heat, some radiators may need more surface area or pipework may need alteration.

That does not mean every radiator must be replaced. The installer should calculate the output required in each room at the proposed flow temperature and identify each change separately.

An air-to-water heat pump normally requires a hot-water cylinder. Homes with a combi boiler may need to create space for one. The quotation should explain cylinder capacity, reheat time, immersion backup and how legionella control is handled.

The cost is affected by the heat pump, cylinder, radiators, pipework, controls, electrical work, groundwork, scaffolding, design and commissioning. A low headline price may exclude work needed to make the whole system operate properly.

A detailed quotation should separate:

• heat-loss survey and system design;
• heat-pump model and rated outputs;
• cylinder and buffer vessel, if used;
• radiator, underfloor-heating and pipework changes;
• controls and weather compensation;
• electrical work and network applications;
• groundwork or outdoor-unit base;
• removal of the old heating system and fuel tank where relevant;
• grant value;
• final amount payable; and
• warranties, servicing and aftercare.

Compare at least three MCS-certified installers if practical. Ask them to explain different assumptions rather than choosing only the lowest price.

The Boiler Upgrade Scheme is installer-led and applies in England and Wales. As checked on 23 September 2026, the main grants are:

• £7,500 for an eligible air-to-water heat pump;
• £7,500 for an eligible ground- or water-source heat pump;
• £2,500 for an eligible air-to-air heat pump; and
• £9,000 for certain eligible off-gas-grid properties installing an air-to-water or ground-source heat pump, available until 31 March 2027.

The grant normally appears as a reduction in the customer’s quotation. The installer applies and must be MCS certified. Do not assume a property qualifies until the current official criteria have been checked.

Scotland and Northern Ireland use different support arrangements. Check the relevant national scheme before budgeting.

Check the current Boiler Upgrade Scheme rules in the official sources below.

Running cost depends on useful heat demand, seasonal performance and the electricity tariff.

Heat-pump electricity use = annual useful heat demand ÷ seasonal performance factor

If a home needs 12,000kWh of useful heat and the seasonal performance factor, or SPF, is 3, the heat pump would use about 4,000kWh of electricity for space heating under those assumptions. Hot water, pumps and backup heating also need to be included where relevant.

SPF measures performance across a season. It is more useful for annual cost comparisons than a laboratory coefficient of performance measured at one outdoor and flow temperature.

Compare delivered heat rather than simply comparing the pence-per-kWh price of electricity and gas. A boiler consumes more fuel energy than the useful heat it supplies because it is not 100% efficient; a heat pump moves additional heat from outside.

Use the comparison calculators with your actual tariff, estimated heat demand, boiler efficiency and a range of plausible SPFs. If removing gas completely, also consider the gas standing charge that would no longer be paid.

A heat pump may reduce carbon emissions and can provide stable, even heating. A boiler is usually cheaper to replace like-for-like and may require less work in a home already designed around high-temperature heating.

The financial result changes with:

• installation cost after grants;
• electricity and gas prices;
• achieved SPF;
• boiler efficiency;
• whether the gas connection remains for cooking;
• maintenance and equipment life; and
• building upgrades required by either option.

Compare heat-pump and gas-boiler costs →

Off-gas-grid homes may have a different case. Heating-oil prices are not protected by Ofgem’s energy price cap and can change quickly. A heat pump removes the need for oil deliveries and tank storage, but the property may need radiator, electrical or building work.

The current £9,000 Boiler Upgrade Scheme rate for certain eligible off-gas-grid properties can materially change the upfront comparison. Check eligibility before treating the grant as confirmed.

Compare heat-pump and heating-oil costs →

Heat pumps often work best when maintaining a steadier temperature rather than producing short bursts of very hot water. Weather compensation can adjust flow temperature as outdoor conditions change. Lower flow temperatures generally improve efficiency, provided the radiators can still meet the room heat loss.

Ask the installer to demonstrate schedules, heating curves, hot-water settings, holiday mode and backup heat. Keep a record of electricity use and comfort during the first heating season so the settings can be refined.

• Obtain a room-by-room heat-loss calculation.
• Check the proposed flow temperature and emitter output in every room.
• Confirm hot-water storage and reheat assumptions.
• Agree the outdoor-unit location and expected sound assessment.
• Check planning requirements and any landlord or freeholder consent.
• Confirm electrical work and network approval.
• Separate the full installation cost from the grant.
• Ask for predicted annual electricity use, not only appliance efficiency.
• Confirm warranties, servicing and responsibility for faults.
• Keep the MCS certificate, commissioning documents and design calculations.