planning

Heat Pump Noise and Neighbours: UK Rules, Decibel Levels and How to Stay Legal

James Mitchell |
heat pump noise neighbours planning permission permitted development decibel levels

Introduction

Noise is one of the most common concerns people raise when considering an air source heat pump. You may worry about the sound disturbing your neighbours, or you may have seen headlines about planning disputes and legal challenges. The reality is far more reassuring than the media coverage suggests. Modern heat pumps are engineered to be quiet, and clear legal rules exist to protect both you and your neighbours.

This guide covers everything you need to know: how loud heat pumps actually are, what the law says, how to position your unit wisely, and what recent policy changes mean for UK homeowners.

How Loud Is a Heat Pump, Really?

Sound is measured in decibels (dB). To put heat pump noise into perspective, here are some familiar reference points:

Sound sourceApproximate level (dB)
Whispering20 to 30
Quiet library30 to 40
Modern heat pump at 1 metre40 to 50
Normal conversation60
Busy road traffic70 to 80
Petrol lawnmower90 to 100

Most modern air source heat pumps produce between 40 and 50 dB when measured one metre from the outdoor unit. At three metres, this drops to around 35 to 42 dB due to the inverse square law. By the time the sound reaches a neighbour's property boundary, it is typically quieter than ambient background noise in a suburban setting.

Ground source heat pumps, by contrast, have no outdoor unit and produce virtually no external noise. If noise is a primary concern and your property allows it, a ground source system eliminates the issue entirely. For a full comparison of the two technologies, see our ASHP vs GSHP guide.

Under permitted development rights in England, an air source heat pump must comply with the MCS 020 Planning Standard, which requires:

The noise level at the nearest neighbour's property boundary must not exceed 42 dB(A).

This is measured as a rating level, which accounts for any tonal or intermittent characteristics of the sound. If the unit produces a noticeable hum or whine, a penalty of up to 6 dB can be added to the measured level when assessing compliance.

Key points about the 42 dB rule:

  • It applies at the nearest habitable building belonging to a different household, measured at the property boundary.
  • The assessment must be carried out by a competent person, typically your MCS-certified installer.
  • If the 42 dB limit cannot be met, you will need to apply for full planning permission.
  • The limit applies to England. Scotland, Wales and Northern Ireland have broadly similar rules but with some regional variations.

Your installer should carry out a noise assessment as part of the design process. If you are concerned about compliance, ask to see the MCS 020 assessment before installation begins. Our installer finder lists only MCS-certified professionals who are trained to carry out these assessments correctly.

The DEFRA Noise Review and Recent Changes

In 2024, the Department for Environment, Food and Rural Affairs (DEFRA) launched a review of permitted development noise conditions for heat pumps. The review was prompted by concerns that the existing 42 dB limit was overly restrictive and was preventing heat pump uptake, particularly in terraced and semi-detached housing.

What Changed

Following the review, the government confirmed in early 2025 that:

  • The 42 dB limit at the nearest boundary remains in place as the primary safeguard.
  • Manufacturers are now required to display prominent noise output data at the point of sale, making it easier for consumers to compare units.
  • MCS updated its guidance to encourage installers to consider low-noise placement strategies as part of standard practice, not just when borderline cases arise.

The review also noted that modern heat pumps are significantly quieter than units installed five to ten years ago, and that noise complaints relating to heat pumps represent a tiny fraction of environmental noise complaints received by local authorities.

The Ed Miliband Factor

Former Energy Secretary Ed Miliband became a vocal advocate for relaxing planning barriers to heat pump installation. His position was that the existing noise rules, while important, should not be used as a blanket reason to refuse installations that can demonstrably meet the 42 dB standard. This political backing helped accelerate the DEFRA review process and contributed to the planning simplifications introduced alongside the Boiler Upgrade Scheme extension to April 2028.

Placement Tips to Minimise Noise

Where you position the outdoor unit makes a significant difference to how much sound reaches your neighbours. Follow these practical guidelines:

1. Maximise Distance from Boundaries

Every doubling of distance reduces sound by approximately 6 dB. If possible, place the unit at least three metres from the nearest boundary. This alone can reduce perceived noise at the boundary by 10 dB or more compared to placing the unit right against a fence.

2. Avoid Reflective Surfaces

Sound bounces off hard, flat surfaces like walls, fences and paving. Placing a heat pump in a corner between two walls can amplify noise by 6 to 9 dB. Position the unit away from corners and L-shaped configurations wherever practical.

3. Use Natural Screening

A dense hedge, earth bank or purpose-built acoustic screen between the unit and the boundary can reduce noise by 5 to 10 dB. Purpose-built acoustic enclosures are available from several manufacturers and are specifically designed not to restrict airflow (which would reduce efficiency).

Important: never fully enclose a heat pump or restrict its airflow. This will reduce performance and can void the manufacturer's warranty.

4. Orient the Unit Thoughtfully

Most of the noise from an ASHP comes from the fan on the front or back of the unit. Where possible, orient the fan so it faces away from the nearest neighbour and towards your own property or an open area.

5. Choose a Low-Noise Unit

Modern premium heat pumps from manufacturers like Vaillant, Daikin and Samsung produce as little as 38 to 42 dB at one metre. When comparing quotes, always check the sound power level (LwA) listed in the product datasheet. A difference of 3 dB may sound small on paper, but it represents a halving of perceived loudness.

6. Consider Anti-Vibration Mounts

Low-frequency vibration can transmit through the ground and into structures, particularly if the unit is mounted on a wall bracket. Anti-vibration mounts and rubber isolation pads are inexpensive additions that can prevent structure-borne noise.

What About Night-Time Noise?

Heat pumps run at their hardest during the coldest hours, which often means overnight. This is also when background noise is lowest, making any mechanical sound more noticeable.

Most modern heat pumps include a "quiet mode" or "night mode" that reduces fan speed and compressor output during specified hours, typically lowering noise by 3 to 5 dB. The trade-off is slightly reduced heating capacity, but for a well-insulated home with good thermal mass, this is rarely noticeable in terms of comfort.

If you are on a smart electricity tariff that offers cheap overnight rates, you may want your heat pump running at full capacity during off-peak hours. In this case, careful placement and a quiet unit become even more important. Read more about how tariffs affect your bills in our running costs guide.

What If a Neighbour Complains?

If a neighbour raises a noise concern after installation, the process typically follows these steps:

  1. Informal discussion: Most issues can be resolved by checking the unit is operating correctly and considering additional screening.
  2. Local authority involvement: If a complaint is made to the council, an environmental health officer may visit to measure noise levels.
  3. Statutory nuisance assessment: The officer will assess whether the noise constitutes a statutory nuisance under the Environmental Protection Act 1990. A heat pump operating within the 42 dB permitted development condition is very unlikely to meet the statutory nuisance threshold.
  4. Remedial action: If noise does exceed acceptable levels, the council may require you to install acoustic screening, relocate the unit or reduce operating hours.

In practice, formal complaints about heat pump noise are rare. According to data from the Chartered Institute of Environmental Health, heat pump noise complaints represent fewer than 0.3 per cent of all noise complaints received by local authorities in England.

Is Your Home Suitable?

Noise considerations are just one part of assessing whether a heat pump is right for your property. Factors such as insulation levels, available space, current heating system and your hot water demand all play a role. Use our suitability checker for a personalised assessment, or try the heat pump calculator to estimate your potential savings.

If you are comparing heat pumps against keeping your existing boiler, our heat pump vs gas boiler guide covers the full picture including cost, carbon savings and comfort.

Frequently Asked Questions

Can I install a heat pump on a terraced house without annoying neighbours?

Yes. Many modern ASHPs produce 42 dB or less at one metre, which means they can comply with the permitted development noise limit even on compact terraced plots. Careful placement, orientation of the fan away from the nearest boundary, and selection of a low-noise unit are essential. Your MCS-certified installer will carry out a noise assessment to confirm compliance before installation.

Is 42 dB really quiet enough not to be heard?

At 42 dB, the sound is roughly equivalent to a quiet residential street with no traffic. Most people find this level easily tolerable, especially when mixed with normal background sounds such as birdsong, wind and distant traffic. Inside a neighbouring property with windows closed, the sound will typically be inaudible.

Do I need planning permission if my heat pump exceeds 42 dB at the boundary?

If the noise assessment shows the unit will exceed 42 dB(A) at the nearest neighbour's boundary, the installation does not qualify for permitted development and you will need to submit a planning application to your local authority. This is not necessarily a barrier, as planning officers will consider the specific circumstances, but it does add time and cost to the process.

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