Thinking about getting a heat pump, but hearing a lot of ‘noise’ about them?

“Are heat pumps noisy?” is one of the questions frequently asked by people in the UK. In reality, heat pumps are not as loud as you might think; in fact, concerns about noise are an almost uniquely British concern.

Europe currently has around 20 million heat pumps installed and the EU has plans to install nearly 60 million more by 2030. These figures strongly suggest that heat pumps are a widely accepted and successful clean energy solution in many other countries.

Recent research conducted by JL Creative found that within a global volume of 1.3k searches for the phrase “are heat pumps noisy” the UK holds the highest figure of 480 monthly searches, compared to 210 searches in Germany, 20 in France and 0 in Spain. This shows the UK is disproportionately apprehensive about heat pumps.

Debunking common noise myths

One popular misunderstanding is that heat pumps will cause noise pollution, particularly in high density residential areas like blocks of flats or streets of terraced housing. A recent report commissioned by Nesta, however, found that the cumulative noise impact of multiple Air Source Heat Pump (ASHP) installations would be no more than typical urban night time noise.

The report further concludes that “even in a worst-case scenario, multiple heat pumps are unlikely to be individually distinguishable from background noise.”

As of April 2021, noise regulations for properties with an ASHP have been put in place. They state that an ASHP must emit no more than 42dB measured from the nearest neighbouring home. Neighbouring properties within 1 metre should not experience noise levels above 42dB. To comply with these standards, it is important that an MCS 020 (Microgeneration Certification Scheme) sound pressure calculation is completed.

A correctly installed and well-maintained heat pump system will mitigate any noise issues as well as offering customers both energy and cost savings.

Noise levels compared to other heating systems

In their earlier generations heat pumps were considered noisy, but manufacturers have addressed this issue and modern models are designed to be quiet. Nesta reports that the average heat pump is no louder than a domestic fridge or boiler.

A range of 40 - 60dB is considered a low to average level of noise, and this volume is normalised in our day to day of modern life. Equivalent to a dishwasher or a microwave, heat pumps produce the same level of noise, which should not be disruptive.

A ground source heat pump (GSHP) is typically the quietest system ranging 40 - 42 dB. This is comparable to birdsong or a laptop. An ASHP ranges 40 - 60 dB, similar to your kitchen refrigerator, a low-level background noise, typically a humming sound that blends into the everyday sounds of home life. An exhaust airsource heat pump (EAHP) ranges 40 - 50db, taking place in the middle of the noise range created by a heat pump.

For perspective, a gas boiler runs between 40-60 dB and characteristically when these systems kick in, there is often some noticeable noise to be heard inside the house. Whereas heat pumps such as the most common type, an ASHP, are installed outside of the home, minimising the sound that you can hear when inside.

The location of your heat pump unit is key. A sound assessment can be carried out prior to installation, ensuring that the heat pump is installed in the correct place to comply with noise regulations.

 NIBE heat pumps are designed to run as quietly as possible and include a silent mode which enables the system to operate at a lower volume when needed, like at night.

Understanding the source of heat pump noise

There are certain audible sounds as part of the normal operations of a heat pump. The important thing to understand is the distinction between functional sounds that demonstrate your heat pump is doing its job and noises that indicate it needs to be checked by an engineer.

As with any mechanical equipment, performance will depend on the age of the system and the quality of installation. Effective installation is critical to minimising noise disturbance.

There are different types of heat pumps, and the noise output will vary depending on the product. Heat pumps have moving parts inside them, such as fans and compressors. Some low-level noise is to be expected if you are within close range of the heat pump (about a metre away). Outside of that boundary, heat pump noise should not be disruptive.

What causes noise in heat pumps?

If you own a heat pump or are considering getting one, it’s helpful to know what sort of noise you should expect to hear and where that sound is coming from.

A useful starting point is to understand the normal operational sounds of a heat pump compared to the noises that signal a problem. A low humming sound indicates ordinary functioning, emitted from the fan pulling warm air into the compressor to generate the necessary heat.

When the heat pump switches to defrost mode during colder weather, it is normal to hear a whooshing sound, and you can expect this sound to increase slightly during the winter months.

Some heat pumps may emit tapping or clicking sounds as the system is turning on and off. Again, this is normal and creates no more noise disturbance than the everyday household appliances found in a typical home.

As part of the heat pump system design process, a certified heat pump installer will ensure that your heat pump is fitted in the right location for your property and any neighbouring properties. Heat pump units must be placed away from windows and bedrooms, to minimise noise disruption.

Troubleshooting heat pump noise

If you are concerned about the noises your heat pump is making, tuning into the scope of sounds can help detect issues.

Ultimately, modern heat pumps are designed to work quietly and if noise levels rise considerably, it could be a signal that something is wrong and you need to call in your heat pump installer to take a look.

Here is an overview of some of the common causes of excessive heat pump noise:

Fans

With an ASHP the most common noise is generated by the fans inside the outdoor unit, which help to circulate the air through the system. Over time the fans can become dirty or worn and this may be the source of increased noise levels., so it is important to have this checked at each service.

Compressor

The compressor is at the heart of the heat pump system and generates heat transfer. With wear and tear, compressors can become noisy through mechanical vibrations. This indicates that it’s time to get your system checked and maintained.

Air flow

If your heat pump is being overworked, it could indicate air flow restrictions, when air intake or exhaust vents are obstructed or blocked, noise may increase. It is important to regularly inspect and clean these vents to ensure optimal airflow.

Season

During the colder months, your heat pump will need to work harder to get up to the desired temperature, so you may experience more noise during winter.

Installation

Heat pumps may make noise if the unit is not levelled or securely mounted. If a heat pump is placed close to walls, this could cause echoes or vibrations. There are simple solutions to prevent these noises, like ‘vibration flexis’ which basically stop vibration of the system pipework or anti-vibration feet for free standing units. These measures should have been taken by a good heat pump installer.

If something is loose, like a screw or hardware component, there may be noises like metal on metal, rattling or loud vibrations. Shrieking, gurgling or buzzing sounds also warrant investigation. If you hear any of these, it’s advisable to get a professional to inspect your heat pump because this could suggest low refrigerant levels or a malfunction of some kind.

A rapid clicking noise accompanied by humming is not to be ignored as this could indicate an electrical fault. Likewise, a hissing sound could indicate escaping air. These have the potential to be major issues and may require maintenance as soon as possible.

In conclusion, all modern heat pumps are designed to run as quietly as possible. If you do have a heat pump that is making too much noise, there is likely to be an issue that needs investigating, so call in an expert.