How noisy are heat pumps compared with a gas boiler?

The figures that matter are these. A heat pump typically runs at 40 to 60 decibels when it is on, a range the consumer body Which? compares to a dishwasher or microwave⁴. The planning limit for a single air source unit is 42 decibels measured one metre from a neighbouring habitable room window⁵. Inside the house, the picture is mixed: one householder reports the system is not louder than the boiler was, while another describes a unit audible in a living room and disturbing sleep in a bedroom above the outdoor unit⁶.

Why noise matters when choosing between a heat pump and a boiler

Noise sits alongside cost in the decisions households actually make. In a 2026 survey, 63% said noise concerns would influence their decision to install a heat pump⁸. That is a large share of the market reacting to something the measured figures describe as modest, and it points to a gap between perception and the decibel range.

The gap shows up elsewhere. Over a third of homeowners surveyed, 37%, said they do not know if a heat pump will perform better than a gas boiler⁹. Cost and electricity prices are often leading people to favour gas boilers, and those two factors are named as important in the decision¹⁰. Noise is not the only uncertainty, but it is the one a neighbour is most likely to raise.

There is a real basis for caution. Air source heat pumps have external fan units that can generate a considerable level of noise, and that is why the planning standards exist¹¹. The rules are not a formality: permitted development depends on staying within the limit, and a unit that fails the assessment needs planning permission¹².

For a household's energy independence, noise is a siting constraint rather than a technical one. A heat pump moves the combustion out of the home entirely, which removes the flue and the boiler casing from the kitchen or airing cupboard. What remains is a fan and compressor outside, and the grid connection that powers it. The trade is a small, continuous outdoor sound for the loss of an indoor appliance.

How many decibels, and what the numbers mean

The headline range is 40 to 60 decibels when the heat pump is on¹². Which? puts air source units at between 40 and 60 decibels on average, a similar noise level to a dishwasher or microwave⁴. Citizens Advice describes the unit as usually quiet, about the same noise level as a fridge³.

The planning figure is tighter than the operating range, and deliberately so. In the UK the legal noise limit for heat pumps is 42 decibels¹⁴. For a single air source heat pump, noise levels must stay at or below 42 decibels measured one metre from any habitable room, for the heat pump on its own⁵. A household cannot normally install a heat pump unless the noise level is 42 dB or less when stood one metre from a neighbouring window¹².

The everyday comparisons and the planning figure are not in conflict. Describing a unit as sounding like a dishwasher or microwave refers to the machine at the point of operation; the 42 dB limit describes what is permitted to reach a neighbour's window⁵. Distance, barriers and the assessment position do the work of closing the gap.

What makes a heat pump noisy, and what makes a boiler noisy

A heat pump's noise comes from two places. Outdoors, the fan and compressor in the external unit do the work, and those fan units can generate a considerable level of noise¹¹. Indoors, the picture depends on the type: indoor units of air-to-air heat pumps can be noisier than other heat pumps¹⁵. The Energy Saving Trust reports that the indoor unit of a heat pump typically makes the same level of noise as a gas boiler when running¹⁶.

Householder experience varies. One case study reports both the outdoor and the indoor unit were noisy while operating¹⁷. Another reports the system is not louder than the boiler was⁶. That spread is normal: the same equipment in different positions, with different barriers and different neighbours' windows, produces different results.

A gas boiler's noise is combustion, a pump and a fan, all inside the building. The material here does not give a decibel figure for a boiler, so no direct number can be set beside the heat pump range. What is documented is that most air source heat pumps produce noise levels similar to a typical gas boiler, and that heat pumps are typically quieter than gas boilers².

For independence, the difference is where the sound sits. A boiler puts its noise inside the home, in a kitchen or utility room, and vents combustion gases through a flue. A heat pump puts its noise outside and takes its energy from electricity, which can be generated domestically or bought from any supplier. The household loses an indoor appliance and gains an outdoor one.

Where the units sit: siting and installation choices that affect noise

Siting is the main lever a household controls. The MCS 020 noise assessment records the installation address, the heat pump installation location, a description of each assessment position, and up to four assessment positions per assessment¹⁸. It also accounts for barriers, including open fencing¹⁸. Two heat pumps and four heat pumps are each supported as assessment cases¹⁸.

The rule the assessment tests is specific: noise levels for an air source heat pump on its own must stay at or below 42 decibels from a metre away from any habitable room⁵. The practical version is that a unit cannot normally be installed unless the level is 42 dB or less when stood one metre from a neighbouring window¹².

Ground source heat pumps change the calculation. They are generally even quieter than air source models, and are described as quieter with increased energy efficiency². The outdoor work happens in a ground loop or borehole rather than a fan unit, so there is no external fan noise at all. That is a siting advantage in tight plots, and it is covered in more detail on ground source heat pumps.

For air source units, the practical questions are distance to the nearest habitable room window, whether a barrier sits between unit and window, and whether the assessment position is realistic. The MCS 020 noise assessment is the document that answers them, and where a heat pump outdoor unit can go covers the siting rules in full.

Do heat pumps make noise at night?

Air source units run when heat is called for, and in cold weather that includes overnight. The material here does not give a separate night-time decibel figure, so the operating range of 40 to 60 decibels and the 42 dB planning limit are the figures that apply¹².

The reported experience is mixed. One householder reports hearing the unit all the time in the living room, sometimes quieter and sometimes louder, with whooshing and startup sounds disturbing sleep in a bedroom above the outdoor unit⁷. That is a single reported case, and it sits against the general finding that most air source heat pumps produce noise levels similar to a typical gas boiler².

Ground source heat pumps are the quieter option at night because there is no external fan². For air source, the assessment position and the barrier between unit and bedroom window decide the outcome. A bedroom directly above an outdoor unit is the configuration most likely to transmit structure-borne sound, and it is the configuration the reported case describes⁷.

Efficiency and running costs: how the two compare

Noise and running cost are usually weighed together, and the cost picture is more contested than the noise picture. At current energy prices, running costs for heat pumps are around the same as for a new gas boiler¹². Nesta reports that bills will likely stay similar under current tariff caps when switching from a gas boiler²⁰.

The savings case depends on conditions. A household could save more than 50% on running costs with a heat pump compared to a gas boiler, but this requires high quality installation, high efficiency and a heat pump tariff²¹. The Energy Saving Trust's latest research shows that switching to a heat pump time-of-use tariff can reduce running costs significantly²². Electric heat pumps use about 3 to 4 times less energy than gas boilers to produce the same heat²³.

Against that, Citizens Advice has found it is typically more expensive to run a heat pump than a gas boiler due to the relative price difference between electricity and gas¹⁹. Gas boilers produce less than one unit of heat for each unit of gas used²⁴. The two positions reflect different tariff assumptions and different installation quality, and the evidence on the typical outcome is not settled.

For independence, the running cost question is really a tariff question. A heat pump on a time-of-use tariff can shift consumption away from peak prices, which a gas boiler cannot do. That flexibility is covered on heat pump running costs and heat pump vs gas boiler running costs.

The phase-out of new gas boilers and what it means for your decision

The government has said it plans to phase out the installation of gas boilers in new homes beyond 2035, though the timeline remains subject to revision²⁶. Nesta records that gas boilers are phased out from new builds from 2025²⁷. The two statements describe different scopes and different dates, and the evidence on the detail is not settled.

What is clear is that existing boilers are not being removed. The material here records no forced removal of existing boilers, and adjustments for current homes are unlikely to be implemented until 2035²⁶. Servicing and repair of an existing boiler are separate from the rules on new installations.

The transition evidence is worth weighing. Households replacing previously functioning gas boilers typically expressed a preference for a new boiler over the heat pump, and those who had previously had working gas or oil boilers were more likely to report an increase in bills or lower satisfaction than their previous system²⁸. That is a finding about satisfaction, not about noise, but it bears on the decision.

Where a boiler is old, a heat pump is worth considering as a much lower carbon alternative to a new boiler²⁹. A heat pump produces up to 70% less CO2 over 15 years than a gas boiler and zero emissions at point of use³⁰. For a household's independence, that shifts the energy source from gas, which is imported and grid-delivered, to electricity, which can be generated on site. The dependence that remains is the electricity supply itself, and the heat pumps and household energy independence page sets out what that means in practice.