Heat Pump Noise: How Loud Are They Really?

The table shows how far a heat pump must be from a neighbour's window to pass the test, using the formula in MCS 020(a). The sound power level comes from the unit's energy label; the worked example in the standard uses 60 dB(A).

How a sound is heard depends on more than its level. MCS guidance notes that tonal, intermittent or unfamiliar sounds are more noticeable, that sound at night stands out more against a quieter background, and that people differ widely in how they perceive sound. That is why placement and a conversation with the neighbours matter as much as the number.

In England and Wales, air source heat pumps can be installed under permitted development, without a planning application, if they meet several conditions. The noise condition is the one most people worry about. Scotland and Northern Ireland also require the MCS planning standard or an equivalent.

The 37 dB(A) limit: The MCS 020(a) calculation must give 37.0 dB(A) or less at an assessment position 1 metre outside the centre of any window or door to a habitable room of a neighbouring home. Habitable rooms are rooms used for sleeping or living, not bathrooms, hallways, utility rooms or rooms used only for cooking. If the unit fails, it is not permitted development and you need to apply for planning permission. The older MCS 020 method had a 42 dB(A) limit but counted differently.

How distance helps: Each doubling of distance cuts the level by about 6 dB. A unit with a sound power level of 60 dB(A), on the ground against a wall, gives about 43.0 dB(A) at 4 metres, which fails, and 37.0 dB(A) at 8 metres, which just passes. Put a solid wall between the unit and the window and the 4 metre figure drops to 33.0 dB(A).

Terraced houses and flats: MCS notes that homes in dense streets find the calculation harder to pass, because units sit closer to neighbours' windows. Careful placement, a quieter model or a barrier can bring the result within the limit. Read our planning permission guide for the full rules.

Unit size and model

Noise varies from model to model. Every heat pump sold in the UK has to be tested for sound power, and the result, in dB(A), is on its energy label. MCS notes that monobloc units, with all their parts outside, generally make more sound than split systems.

When comparing quotes, ask each installer for the sound power level of the specific model they propose. It is the number the planning calculation starts from, and a quiet mode figure does not count.

Operating mode

A heat pump is more noticeable when it works harder: in winter, when it is heating hot water and during defrost cycles, when it clears ice from the outdoor coil. That is normal, but it is worth planning around, for example by heating hot water outside sleeping hours.

Placement

Where you put the outdoor unit makes a big difference. Hard surfaces within 1 metre of the unit reflect sound and raise the level, and corners and enclosed spaces amplify it. MCS advises facing the unit away from neighbouring windows and your own habitable rooms, and avoiding corners, enclosed areas and hollow spaces, which can amplify noise. More than three reflecting surfaces, as in a lightwell, fails the calculation outright.

Vibration

A heat pump fixed straight to a wall or plinth can pass vibration into the building, which is heard indoors as a low hum separate from the airborne noise. MCS advises against mounting units next to bedrooms or on structures that carry vibration, and recommends anti-vibration feet, pads or rubber grommets.

Choose a quiet unit. Compare sound power levels on the energy labels when you get quotes. A lower figure can be the difference between needing a barrier, or a planning application, and not.

Maximise distance. Each doubling of the distance to your neighbour's window cuts the level by about 6 dB. A position further down the garden helps, though longer pipe runs can add cost.

Use anti-vibration mounts. Rubber feet, pads, platforms or grommets between the heat pump and its plinth or wall stop vibration reaching the building, and MCS notes they may also help the unit last longer.

Avoid reflective surfaces, and use barriers. Do not box the unit in with hard walls. A solid wall or fence at least 18mm thick that hides the neighbour's window from the unit counts as a 10 dB reduction in the calculation, and acoustic fencing can both block and absorb sound. Hedges and gappy fences do not count as barriers.

Ask about a compressor jacket. An insulation jacket round the compressor gives around 6 dB off the compressor's noise, according to MCS, but check with the manufacturer first, because fitting one afterwards may affect the warranty.

Maintain the unit. MCS notes that a lack of maintenance can make a heat pump louder over time. Keep the fan clear of leaves and debris and have loose panels or worn parts fixed.

Use quiet modes and scheduling with care. Quiet or eco modes slow the fan and compressor, but they can also cut heat output and efficiency. Scheduling hot water outside common sleeping times is often the better fix.

Even when your heat pump meets all planning conditions, a conversation with your neighbours before installation prevents problems later. MCS advises consulting anyone within earshot as early as possible and explaining what they will hear.

Before installation: Let your immediate neighbours know you are installing a heat pump, where the outdoor unit will go and what it will sound like. Showing them the installer's MCS 020(a) result for their window is often reassuring.

If a neighbour complains: MCS suggests checking for a failed or loose component, making sure servicing is up to date, checking whether anything has changed around the unit, such as a removed fence, and then trying quiet modes, scheduling or mitigation such as a barrier.

Statutory nuisance: A neighbour can complain to the council whether or not the unit meets the planning conditions. In England, councils must look into noise that could be a statutory nuisance under the Environmental Protection Act 1990, meaning it unreasonably and substantially interferes with the use or enjoyment of a home, or harms health. If the council finds a nuisance, it must serve an abatement notice.

The outdoor unit is the main noise source. MCS lists circulating pumps alongside the compressor and fan as the parts that make sound, so you may hear a pump indoors, and a unit fixed without anti-vibration mounts can pass a hum into the building.

A heat pump is most noticeable when it works hardest, in cold weather, which is also when it is least efficient. In the Electrification of Heat trial, the median heat pump ran at 3.37 units of heat per unit of electricity at 10°C outside, but 2.37 at minus 3°C. A well-insulated home needs less from the heat pump on the coldest days. This is another reason to insulate your home before or alongside a heat pump installation.

Read our running costs guide for how insulation and tariff choice affect your bills. Use our heat pump calculator for a cost estimate that accounts for your insulation level.

Noise test from MCS 020(a) Issue 1.1. Noise advice from the MCS Installation Guidance for Mitigating Noise from Air Source Heat Pumps. Planning rules from legislation.gov.uk. Nuisance law from GOV.UK. Efficiency by outdoor temperature from the Electrification of Heat trial. All checked on 25 September 2026.