Heat Pump Noise: We Measured 20 Installations. Here Is the Truth

Heat pump noise is one of the most persistent concerns among UK homeowners considering the switch. Online forums are full of worst-case anecdotes, and planning objections frequently cite noise as a reason to oppose installations. But what do the actual numbers show? We decided to find out — not from manufacturer spec sheets, but from real installations in real UK homes.

We visited 20 heat pump installations across England, Scotland, and Wales with a calibrated Class 2 sound level meter. We measured noise at 1 metre from the unit, at the property boundary, and from inside the home with windows open and closed. We tested during normal heating operation and during defrost cycles. Here is what we found.

Our Methodology

We measured each installation under the following conditions:

• Outdoor temperature: 2-8°C (typical UK winter heating conditions)
• Heat pump operating at normal heating load (not maximum)
• Measurements taken at 1m from unit, at property boundary, and from inside the home
• Background noise measured separately to establish ambient levels
• Calibrated Class 2 sound level meter (LAeq, 5-minute measurement periods)
• Wind speed below 5 m/s during all measurements

The installations covered 8 different brands, 12 different models, and property types from terraced houses to detached rural homes. This gives a representative picture of what real heat pump noise looks like across different situations.

The Results: 20 Installations Measured

All measurements taken during normal heating operation at 2-8°C outdoor temperature. LAeq 5-minute measurements using calibrated Class 2 meter.

Putting Decibels in Context

Numbers mean nothing without context. Here is how our measured heat pump noise levels compare to everyday sounds:

The average heat pump at the property boundary (32dB) is quieter than a domestic fridge and significantly quieter than birdsong. Even standing directly next to the unit (42dB), it is quieter than a normal conversation. And crucially, a gas boiler's external flue noise — which nobody complains about — is typically louder than a heat pump.

Noise by Brand: Which Are Quietest?

Based on our measurements, here is how the brands compared (averaging across models and sizes):

Averages from our 20-installation sample. Larger units are naturally slightly louder. All brands measured are well within acceptable noise limits. Brand reviews: Stiebel Eltron, Vaillant, Nibe.

Stiebel Eltron and Vaillant led on noise performance, with the quietest units we measured at just 36dB — quieter than a quiet library. However, all brands fell well within acceptable noise limits, and the differences between them are small enough that placement and installation quality matter more than brand choice.

How Distance Reduces Noise

Sound follows the inverse square law: doubling the distance reduces the perceived noise by approximately 6dB. This is why placement matters so much. A heat pump that measures 42dB at 1 metre will measure approximately:

• 36dB at 2 metres
• 30dB at 4 metres
• 24dB at 8 metres

At 8 metres — a typical distance to a neighbour's house in a suburban setting — the unit is quieter than a whisper. Walls, fences, and hedging provide additional sound attenuation on top of distance reduction.

Defrost Cycle Noise

The defrost cycle — when the heat pump briefly reverses to melt frost from the outdoor heat exchanger — is the loudest moment in normal operation. We measured defrost noise at 5 installations and found it added 3-8dB above normal running noise, lasting 2-5 minutes. At 1 metre, this meant momentary readings of 45-52dB — comparable to light rain or quiet office noise. At the property boundary, defrost noise remained below 40dB in all cases.

Defrost cycles are most frequent at 0-5°C with high humidity. In very cold, dry weather (below -5°C), defrost occurs less frequently. The cycles are a normal part of operation and are accounted for in planning noise assessments.

Placement Matters More Than Brand

Our single biggest finding was that placement has more impact on perceived noise than brand or model choice. The same unit positioned against a flat wall in a corner (which amplifies sound through reflection) was noticeably louder than the same unit positioned on an open side of the house with space around it.

Best practices for minimising noise through placement include:

• Avoid positioning directly under bedroom windows
• Keep 300mm minimum clearance from walls for airflow and noise reduction
• Avoid corner positions where two walls create sound reflection
• Position on the side of the house facing away from neighbours where possible
• Use anti-vibration mounts on the base to prevent structure-borne noise

A good installer will assess placement options during the survey and recommend the position that optimises both airflow and noise impact.

Planning Rules and Noise Limits

Under permitted development rules, air source heat pumps in England must comply with MCS 020 noise standards. The key requirement is that the noise level must not exceed 42dB at 1 metre from the nearest neighbouring habitable room window. MCS-certified installers are required to conduct a noise assessment as part of every installation and demonstrate compliance.

In Scotland, Wales, and Northern Ireland, similar rules apply with slight variations. In conservation areas and listed buildings, additional planning conditions may apply. Your installer should handle all noise compliance as part of the installation process.

The FOI Complaint Data

We submitted Freedom of Information requests to 50 UK councils asking about heat pump noise complaints. The data, which we analyse in detail in our FOI noise complaints article, showed remarkably low complaint rates. Across councils representing over 10 million residents, heat pump noise complaints averaged fewer than 2 per council per year — a fraction of complaints about barking dogs, music, or construction noise.

The data confirms what our measurements show: properly installed heat pumps are not a significant source of noise disturbance. The vast majority of the quarter-million-plus UK installations operate without any noise issues whatsoever.

Frequently Asked Questions

How loud is a heat pump?

Our measurements found 36-47dB at 1 metre (average 42dB) — comparable to a quiet library or domestic fridge. At the property boundary, levels were 26-38dB — quieter than a whisper in most cases.

Can you hear a heat pump from inside?

In 17 of our 20 installations, the unit was completely inaudible from inside with windows closed. With windows open near the unit, a faint hum was occasionally detectable.

Are heat pumps louder than air conditioning?

No. Modern heat pumps (35-50dB) are quieter than typical air conditioning condensers (50-65dB). Inverter technology means they run quietly at part load most of the time.

Do heat pumps get louder in cold weather?

Slightly — the compressor runs harder, adding 3-5dB. Even at maximum output, modern units typically stay below 50dB at 1 metre. Defrost cycles add brief 3-8dB increases lasting 2-5 minutes.

Will my heat pump annoy my neighbours?

Very unlikely with proper placement. At typical boundary distances (3-5m), noise drops to 28-38dB — below background noise in most suburban and urban environments.

Which brands are quietest?

Stiebel Eltron, Vaillant, and Nibe recorded the lowest noise levels in our tests (36-40dB average). All brands met noise requirements comfortably.