Heat Pumps Compared with Boilers

A heat pump and a boiler do the same job by opposite means. A boiler burns a fuel and releases heat; a heat pump uses electricity to move existing heat from the air, the ground or water into the home. That difference is the whole comparison: it sets the efficiency, the running cost, the emitters the system needs, and the amount of the household's energy supply it still depends on.

The efficiency gap is large and consistent across official sources. Heat pumps can be over three times more efficient than boilers¹, and the amount of energy needed can be less than a third of what a gas boiler needs to produce an equivalent amount of heat². The Climate Change Committee puts heat pumps at around three to four times more efficient than gas boilers, which it says should lead to lower household energy bills³. Heat pumps and similar technologies typically reduce energy use by at least three times compared with boilers⁴.

The cost picture is less flattering at the point of purchase. An average heat pump is around £11,600, currently four times more expensive than a gas boiler⁵, and installation costs are higher than gas boilers in part because of the additional retrofitting a heat pump system usually needs⁷. The Boiler Upgrade Scheme pays £7,500 towards an air-to-water heat pump and £7,500 towards a ground source heat pump, including water source heat pumps and those on shared ground loops⁸.

The short answer: efficiency against purchase price

A heat pump is the more efficient machine and the boiler is the cheaper one to buy. Which costs less to run over a year depends on the price of electricity against the price of gas, and on how well the system is designed for the house it serves.

The efficiency advantage is not marginal. Heat pumps, both for individual homes and large-scale ones for heat networks, use electricity as the energy source and are typically over three times more efficient than the most efficient gas boilers or electric heaters¹⁰. The Scottish Government's own assessment puts it in the same terms: the higher efficiency of a heat pump means the amount of energy needed can be less than a third of the amount needed by a gas boiler to produce an equivalent amount of heat².

That is a statement about energy, not about money. A heat pump that uses a third of the energy still pays the electricity unit rate for it, and electricity has historically cost more per unit than gas. The comparison therefore turns on the ratio between the two unit prices, which is exactly the test the government's own heat pump methodology applies to hybrid systems: the ratio of the heat pump's coefficient of performance to the boiler's efficiency must be greater than the ratio of the unit costs of the heat pump's energy source and the boiler's energy source¹³. Where that condition holds, the heat pump is the cheaper way to produce the heat. Where it does not, it is not.

For a household, the practical answer is that a heat pump is a different heating system rather than a like-for-like appliance swap. It runs at lower flow temperatures, it needs emitters sized to deliver the same heat at those temperatures, and it normally needs a cylinder for hot water. Those requirements, not the machine itself, are what drive the installation cost and the disruption.

The figures: cost, carbon and grant

The figures that matter fall into three groups: what the system costs, what it saves in energy and carbon, and what the grant covers.

On cost, the Boiler Upgrade Scheme statistics for 2026 Q2 give a nominal median installation cost of £12,908 for an air-to-water heat pump and £27,232 for a ground source heat pump, both including the grant value, in England and Wales⁸. The reported range around those medians is wide, and the median installed capacity differs by technology⁸:

The parliamentary figure of around £11,600 for an average heat pump, four times a gas boiler, is a separate and earlier comparison⁵.

On energy and carbon, the government's consumer-facing guidance states that a heat pump produces up to 70% less CO2 over 15 years than a gas boiler and zero emissions at the point of use⁹. The Scottish Government's assessment states that the higher efficiency of a heat pump means the amount of energy needed can be less than a third of that needed by a gas boiler for equivalent heat¹². An earlier government study of hybrid heat pumps modelled a carbon saving of 690 to 950 kgCO2 per year, or 24 to 34%, against a condensing gas boiler counterfactual¹⁵.

On the grant, the position from 21 July 2026 is £7,500 towards an air-to-water heat pump and £7,500 towards a ground source heat pump, including water source heat pumps and those on shared ground loops¹⁵. Air-to-water vouchers are valid for three months and ground source vouchers for six months¹⁵. The scheme has issued 116,832 vouchers and paid 88,092 redemptions between May 2022 and July 2026, with 140,474 applications received, 98% of them for air-to-water installations⁸.

What drives the numbers

Three things drive the figures: the compressor, the temperature difference it has to work across, and the emitters that deliver the heat.

Most heat pumps use an electrically driven compressor¹³, and the compressor must be driven by electricity¹⁶. The heat itself comes from air, ground or water¹⁸. Because the machine moves heat rather than creating it, the efficiency is a multiple rather than a percentage, and that multiple is what produces the three-to-four-times comparison with gas boilers³.

The efficiency is not fixed. The higher the temperature difference between the heat source and the target heat, the harder the compressor works and the more electricity it requires¹⁹. This is the single most important design fact in the comparison. A heat pump feeding radiators sized for a higher flow temperature will work across a larger temperature difference than one feeding underfloor heating or oversized radiators at a lower flow temperature, and it will use more electricity for the same heat. Cold weather raises the temperature difference from the source side; a high flow temperature raises it from the target side. Both push electricity use up.

That is why the emitter question is not cosmetic. A wet system has to distribute heat using a liquid¹⁶, and the heat pump must be capable of meeting the full space heating and hot water heating demands of the property²⁰. A system that meets the space heating demand at a low flow temperature but cannot recover the house on the coldest day has been sized or specified wrongly, and the household experiences it as a heating system that never quite gets there.

Cold weather: output holds, running cost rises

Heat pumps work in cold weather, and the reason is in how they are specified rather than in how they behave on a mild day. A heat pump is sized for the coldest design condition the property is expected to see, so the output is there when the temperature drops. What changes is the cost of producing it.

The mechanism is the temperature difference. As the outside air gets colder, the gap between the source and the target heat widens, the compressor works harder, and the electricity required rises¹⁹. A ground source heat pump is less exposed to this because the ground temperature is more stable than the air temperature, which is part of why ground source installations carry a higher capital cost and a lower running sensitivity to weather.

The practical consequence for a household is that a cold snap shows up on the electricity bill rather than in a failure to heat. It also means the annual running cost depends heavily on how the system is controlled: a heat pump run at a steady low flow temperature for long periods performs differently from one cycled on and off at a high flow temperature, and the design should reflect that.

The carbon position is unaffected by the weather in the way the cost position is. A heat pump produces zero emissions at the point of use and up to 70% less CO2 over 15 years than a gas boiler⁹, because the emissions sit at the power station rather than at the flue. As the grid decarbonises, that figure improves; as the outside temperature falls, the running cost rises. The two are separate questions and are often conflated.

England, Scotland, Wales and Northern Ireland

The grant and the regulatory framework are not the same in all four nations, and the differences matter to what a household can claim and what it must comply with.

The Boiler Upgrade Scheme operates in England and Wales, which is why the published statistics cover those two nations⁸. Scotland runs its own support through Home Energy Scotland rather than through the Boiler Upgrade Scheme, and its Heat in Buildings Strategy sets a different trajectory: a proposed backstop date of 2045 for low or zero emissions heating in existing buildings¹², and a pathway for all buildings to use zero emissions heating and cooling systems by 2045¹⁸. The remainder of existing fossil fuel based heat networks was to decarbonise by 2045 at the latest¹⁸.

Wales has its own building regulations position: installation of either a ground source or air source heat pump will have to comply with the Building Regulations²². The Welsh strategy also refers to plans to phase out the installation of all new gas boilers beyond 2035, and sets out a regulatory route map for phasing out all new gas boiler installations for commercial properties by 2033²³.

Northern Ireland is not covered by the Boiler Upgrade Scheme statistics in the same way, and the grant position there is administered separately. Where a household is considering a heat pump, the nation it sits in determines which scheme applies, which conditions attach, and which building regulations the installation must satisfy.

The rules: grant conditions, planning and building regulations

The rules fall into two layers: what the grant requires of the system, and what planning and building regulations require of the installation.

For the grant, the heat pump must provide both space and hot water heating and be capable of meeting the full space heating and hot water heating demands of the property²⁰. It must distribute heat using a liquid¹⁶, and it must have a compressor driven by electricity¹⁶. Those conditions rule out air-to-air systems, which are not considered a renewable system in ECO4²⁴. A ground source heat pump may also be comprised of a shared ground loop, treated as a district heating variant measure type under ECO4²⁴.

For planning, an air source heat pump usually falls under permitted development if it meets a set of conditions:

• The installation must comply with the Microgeneration Certification Scheme Planning Standards (MCS 020a)²⁵.
• The outdoor compressor unit must not exceed 1.5 cubic metres on a house or 0.6 cubic metres for a block of flats²⁵.
• All parts must be at least one metre from the property boundary²⁶.
• Installations on pitched roofs are not permitted development²⁵, and on a flat roof all parts must be at least one metre from the external edge²⁵.
• Only the first installation is permitted development on a house which is not detached or a block of flats; for detached houses, the first two are permitted development²⁵.
• Permitted development rights do not apply within the curtilage of a listed building or within a site designated as a scheduled monument²⁵.

Noise is the condition most likely to catch a household out. Noise levels for an air source heat pump on its own must stay at or below 42 decibels, measured a metre from any habitable room²⁶. Where the unit exceeds the MCS standards and permission is needed, noise must not exceed 37 dB LAeq at any time, measured on the boundary of the site with any neighbouring residential property²⁷. In a conservation area or World Heritage Site the unit must not be installed on a wall or roof which fronts a highway²⁵.

Ground source heat pumps on domestic premises are usually considered permitted development and do not need a planning application²⁸. In a listed building or conservation area, the council should be contacted to check local requirements²⁸. Building Regulations parts A to T apply to air source heat pumps, plus Regulation 7²⁶, and gas boilers must have a minimum efficiency of 86% for gas and 85% for oil²⁹.

What it means for energy independence

A heat pump changes what a household depends on. It removes the gas supply from the heating system and replaces it with electricity, and it reduces the amount of energy the home needs to buy in the first place. It does not make the home self-sufficient.

The reduction is real and measurable. Heat pumps and similar technologies typically reduce energy use by at least three times compared with boilers⁴, and the amount of energy needed can be less than a third of a gas boiler's for equivalent heat². A household that needs less energy is less exposed to price movements in whatever it buys, and a household that no longer buys gas has removed one fuel supply, one standing charge and one set of safety obligations from the property.

What remains is electricity. The home still draws from the grid, still depends on a supplier and a tariff, and still depends on the network being able to deliver the load. The compressor, the controls and any monitoring app remain the manufacturer's, which is a dependence that does not appear on an energy bill but is real: a system whose controls are tied to a company's servers or a discontinued app is a system with a third party in the middle of it.

The wider industrial picture is that the technology is a UK export opportunity as well as a domestic one. Air source heat pumps represent the most promising export opportunity, contributing 35% of export driven GVA by 2050, and cumulative cost savings in the High Diversification scenario at the high innovation level reach £110.8bn in 2050, compared with £67.8bn and £71.7bn in the High Hydrogen and Minimally Constrained scenarios³⁰.

For the household, the honest summary is that a heat pump trades a gas dependence for an electricity dependence and reduces the total energy required. That is a meaningful shift in a home's position, and it is not independence. The heating and energy independence page sets out the wider picture, and the boilers and home heating guide covers how the alternatives compare.