Are Heat Pumps Noisy?

It is one of the most common concerns. You have heard that heat pumps have an outdoor unit, and you are picturing something that sounds like an air conditioning unit on a Spanish hotel. The reality is very different.

How Loud Are Modern Heat Pumps?

A modern air source heat pump operates at around 40–45 decibels when running. That is roughly the same as a fridge humming in your kitchen, or a quiet library. Here is how that compares to everyday sounds:

Sound	Decibel Level
Whispering	30 dB
Fridge	40 dB
Air source heat pump	40–45 dB
Normal conversation	60 dB
Washing machine	70 dB
Lawnmower	90 dB

If you stand right next to the outdoor unit, you will hear a low, steady hum. Step a few metres away and it fades into the background. From inside the house, most people cannot hear it at all.

The Planning Rules on Noise

Under permitted development rules, an air source heat pump must not exceed 42 decibels at the nearest neighbour's property boundary. This is measured as an MCS noise assessment, which every accredited installer (including us) carries out before installation.

In practice, meeting this limit is straightforward. Sound drops off quickly with distance. A unit producing 45dB at one metre will typically be well under 42dB by the time the sound reaches a boundary three or four metres away.

Why Placement Matters

Where we position the outdoor unit makes a real difference. We consider several factors:

• Distance from neighbour boundaries — further away means quieter at their end.
• Reflecting surfaces — placing a unit in a tight corner between two walls can amplify the sound. We avoid this.
• Bedroom windows — yours and your neighbours'. We try to keep the unit away from sleeping areas.
• Airflow — the unit needs good airflow to work efficiently, so it cannot be completely boxed in.

Good positioning is part of good installation. We plan this carefully during the survey so there are no surprises.

What About Older Heat Pumps?

If you have heard a noisy heat pump, it was probably an older model or a poorly installed one. The technology has improved dramatically in the last five to ten years. Modern inverter-driven units ramp up and down smoothly rather than switching on and off at full blast. They are quieter at startup, quieter under load, and quieter at idle.

Will My Neighbours Complain?

It is a fair concern, especially if you live in a terraced house or have close neighbours. In our experience, once the unit is installed and running, neighbours are usually surprised by how quiet it is. Most cannot hear it from their garden, let alone inside their home.

If you are worried, we can show you the MCS noise assessment results before installation. You will see exactly what the predicted noise level will be at your neighbour's boundary.