Heat Pump Noise: What to Expect and How to Reduce It
TLDR: Air source heat pump outdoor units produce 40-60 dB at 1 metre. This is quieter than a conversation but audible nearby. Noise is regulated under planning rules (42 dB at neighbour's window). Proper placement, acoustic enclosures, and modern inverter units minimise impact. This comprehensive guide covers everything British homeowners need to know about heat pump noise.
The Noise Question Everyone Asks
Let's address the elephant in the room straight away. One of the most common concerns we hear from homeowners considering heat pumps is about noise. Will the outdoor unit disturb your sleep? Will the neighbours complain? Is it going to sound like a helicopter landing in your garden every time the heating comes on?
The short answer is no. Modern heat pumps are remarkably quiet—far quieter than many people expect. But the longer answer requires understanding exactly what creates noise, how sound is measured, and what you can do to minimise any impact.
We've spoken to dozens of homeowners across Britain who've installed heat pumps in the past few years. Their experiences, combined with technical data and planning regulations, paint a clear picture of what to expect.
How Loud Are Heat Pumps Really?
Sound is measured in decibels (dB). The scale is logarithmic, which means every 10 dB increase represents a tenfold increase in sound intensity. Here's how heat pumps compare to everyday sounds:
| Sound Source | Decibels |
|---|---|
| Quiet whisper | 30 dB |
| Refrigerator humming | 40 dB |
| Modern heat pump (at 1 metre) | 40-55 dB |
| Normal conversation | 60 dB |
| Gas boiler (indoor) | 45-60 dB |
| Old air conditioning unit | 55-65 dB |
| Vacuum cleaner | 70 dB |
| Lawnmower | 90 dB |
Modern inverter-driven heat pumps are 10-15 dB quieter than older fixed-speed models. The best units on the market today—from manufacturers like Vaillant, Daikin, and Samsung—run at 40-45 dB in normal operation. That's roughly equivalent to the hum of your fridge.
Context matters enormously here. A 45 dB heat pump positioned 5 metres from your bedroom window, behind a fence, is essentially inaudible inside your home. The same unit positioned 1 metre from a neighbour's bedroom window with no barriers would be a different story entirely.
What Actually Creates the Noise?
Understanding where heat pump noise comes from helps you manage it effectively.
The Outdoor Unit
This is where virtually all the noise originates. The outdoor unit contains:
- The fan: This is the primary noise source. The fan draws air across the heat exchanger to extract heat energy. It creates a consistent, low-frequency whirring sound.
- The compressor: This creates a lower-frequency hum. Modern inverter compressors are much quieter than older technology because they modulate speed rather than cycling on and off.
- Defrost cycles: In cold, humid weather, frost can build up on the outdoor unit. Periodic defrost cycles are slightly louder than normal operation and involve the fan running at higher speeds temporarily.
The Indoor Unit
Indoor components are much quieter:
- Circulation pump: Creates minimal sound, similar to a central heating pump you might already have.
- Water flow through pipes: Barely audible, like existing central heating systems.
- Fan coil units: If you're using fan convectors rather than radiators, these create a gentle airflow sound similar to a bathroom extractor on low.
Real Homeowner Experiences
Numbers only tell part of the story. Here's what British homeowners actually experience with heat pump noise.
Sandra and Michael, Guildford (4-bed detached): "We were genuinely worried about noise before installation. Our neighbours are quite close, and we didn't want to cause issues. The installer positioned our Vaillant Arotherm Plus behind the garage, facing away from both houses. Honestly, we forget it's there. You can hear it if you stand right next to it, but from inside the house or the garden seating area, nothing. The neighbours said they haven't noticed anything at all. Our old boiler was louder when it fired up."
David, Leicester (3-bed semi): "I'll be honest—I can hear our heat pump from the bedroom on winter nights when everything's quiet. It's a gentle hum, nothing intrusive. My wife says she finds it soothing, like distant traffic. We had the unit installed on the side passage, and I added a small acoustic screen for about £300. Made a noticeable difference. Compared to the oil boiler we replaced, which used to shake the whole house when it started, it's night and day."
Helen and Robert, Edinburgh (Victorian terrace): "Our main concern was the shared boundary with next door. The installer suggested a Samsung Gen7 unit, which is one of the quietest on the market at 35 dB. We also had it mounted on anti-vibration pads. Cost an extra £80 but worth it. Three months in, the neighbours have commented on how quiet it is—they were expecting much worse based on what they'd read online."
Graham, Plymouth (2-bed bungalow): "My bedroom is about 4 metres from the outdoor unit. The first week, I noticed it. Not loud, just new. After a fortnight, I stopped noticing entirely. Your brain tunes it out like any consistent background sound. What I do notice is the defrost cycle in winter—it runs for a few minutes every few hours when it's really cold. Even that's just a slightly louder hum. Nothing that wakes me up."
Planning Regulations and Legal Requirements
Heat pump installations in the UK fall under permitted development rights, provided they meet certain criteria. For noise, the key requirement is:
- 42 dB or less at the nearest neighbouring property's habitable room window
- 1 metre minimum from the property boundary
The 42 dB limit is measured at the nearest neighbour's window, not at the unit itself. This is crucial to understand. A unit producing 48 dB at 1 metre will measure approximately 42 dB at 2 metres, and 36 dB at 4 metres. Sound intensity reduces by 6 dB each time the distance doubles.
How Installers Ensure Compliance
Any MCS-certified installer will calculate noise levels as part of the installation design. They'll consider:
- The manufacturer's stated noise output at various operating modes
- Distance to neighbouring properties
- Reflective surfaces (walls, fences) that might amplify sound
- Any existing barriers or proposed acoustic measures
If compliance can't be achieved through positioning alone, installers may recommend acoustic barriers, quieter unit models, or alternative placement locations.
Comprehensive Noise Reduction Strategies
1. Optimal Unit Placement
Position is the single most important factor in managing heat pump noise. Good placement can make the difference between a unit that's inaudible and one that causes issues.
- Maximise distance from boundaries: Every metre helps. Position the unit as far from neighbours as practically possible.
- Face the fan away from windows: The fan outlet is the noisiest direction. Point it away from both your windows and your neighbours'.
- Avoid corners: Sound reflects off walls and can amplify in corner positions. Open areas dissipate sound more effectively.
- Use existing structures: A position behind a garage, shed, or solid fence provides natural sound absorption.
- Consider airflow requirements: Units need clear space around them for airflow. Don't position in enclosed spaces or directly against walls.
2. Acoustic Barriers and Enclosures
Purpose-built barriers can significantly reduce noise transmission:
- Acoustic fencing: Specialist acoustic fence panels cost £200-£500 for a typical installation. They're designed to absorb and deflect sound waves.
- Purpose-built enclosures: Manufacturers like Quiet Mark offer enclosures designed specifically for heat pump units. These cost £300-£800 but can reduce noise by 5-10 dB.
- Planting hedges: A long-term solution. Dense evergreen hedging like laurel or privet provides year-round screening and modest sound absorption.
- Existing walls and fences: A solid 1.8m fence between your unit and neighbours provides meaningful noise reduction at no additional cost.
Important note: never fully enclose a heat pump. Units require airflow to function correctly. Any enclosure must have adequate ventilation openings.
3. Anti-Vibration Measures
Vibration can transmit sound through the ground and into building structures. Proper mounting prevents this:
- Rubber mounting pads: Cost £50-£100. These isolate the unit from its base, preventing vibration transmission.
- Concrete plinth with damping: A properly constructed base with vibration-absorbing layers costs £200-£400.
- Wall-mounted anti-vibration brackets: If wall-mounting is necessary, specialist brackets prevent vibration transfer to the building structure.
4. Choosing a Quieter Unit
Noise levels vary significantly between manufacturers and models. Some of the quietest units currently available include:
- Samsung EHS Mono HT Quiet (Gen7): 35 dB at 1m in quiet mode
- Vaillant Arotherm Plus: 38-43 dB depending on size
- Daikin Altherma 3: 37-45 dB
- Mitsubishi Ecodan: 40-48 dB
When comparing units, look at noise levels at partial load (where the unit runs most of the time) rather than just maximum capacity figures.
Seasonal Variations in Noise
Winter Operation
Heat pumps work harder in winter, which can affect noise in several ways:
- Longer running times: The unit runs for extended periods to maintain home temperature, though modern inverter units run continuously at lower power rather than cycling on and off.
- Defrost cycles: In cold, humid conditions, frost builds up on the outdoor unit. Periodic defrost cycles (typically every 1-4 hours in freezing conditions) run the fan at higher speeds for 5-15 minutes.
- Higher power operation: During very cold spells, the compressor works harder, which can increase noise slightly.
Modern units with smart defrost algorithms minimise defrost frequency and duration. The latest Samsung and Vaillant units, for example, use sensors to defrost only when actually needed rather than on fixed schedules.
Summer Operation
If your heat pump provides hot water year-round, it will still run in summer—but at much lower intensity. Summer operation is typically quieter than winter because the unit works less hard to extract heat from warmer air.
Some heat pump models can also provide cooling in summer. Cooling operation involves similar noise levels to heating.
Addressing Neighbour Concerns
Proactive communication prevents problems. Here's how to handle the neighbour conversation:
Before Installation
- Inform neighbours about your plans in advance
- Explain that modern units are quiet and regulated
- Show them where the unit will be positioned
- Offer to share noise data from the manufacturer
- Discuss any acoustic measures you're planning
After Installation
- Check in with neighbours after a few weeks to ask if they've noticed anything
- Be open to feedback and willing to add acoustic measures if needed
- Keep records of any communication in case of future disputes
In our experience, neighbours who are consulted beforehand rarely complain. It's surprise installations that cause friction—not the noise itself.
Ground Source: The Silent Alternative
If outdoor noise is a major concern and budget allows, ground source heat pumps eliminate it entirely. There's no outdoor unit—just underground pipes and an indoor heat pump unit.
Indoor ground source units produce similar noise to a large fridge-freezer: 42-48 dB. This sound stays inside your plant room or utility space.
The trade-off is cost: ground source installations run £15,000-£25,000 compared to £8,000-£15,000 for air source. But for noise-sensitive situations—properties with very close neighbours, bedrooms adjacent to the only viable installation location, or homeowners who are particularly sensitive to sound—ground source offers peace of mind.
Frequently Asked Questions
Q: Will my neighbours complain about heat pump noise?
A: Properly installed units meeting planning regulations rarely generate complaints. Problems typically occur with older, louder models, poor positioning, or installations that don't meet the 42 dB limit. Discuss your plans with neighbours beforehand—transparency prevents problems.
Q: Is a heat pump louder than my old gas boiler?
A: Typically not. Gas boilers produce 45-60 dB when firing—similar to or louder than most heat pumps. The difference is location: boiler noise is inside your home, while heat pump noise is outside. Most homeowners find heat pumps quieter overall because the outdoor location means you hear less indoors.
Q: Can I run the heat pump at night?
A: Yes. Most units have night modes or quiet modes that reduce fan speed and operating noise. Heat pumps often run most efficiently overnight when taking advantage of time-of-use electricity tariffs. The consistent, low-level sound is less intrusive than a boiler cycling on and off.
Q: What if my installation doesn't meet the 42 dB requirement?
A: You'll need to add acoustic measures (barriers, enclosures) or choose a quieter unit model. If compliance still can't be achieved, the installation may require formal planning permission rather than permitted development rights. Your installer should identify this during the design phase.
Q: Does noise increase over time as the unit ages?
A: Well-maintained units shouldn't become significantly noisier. Fan bearings and compressor components can wear over time, potentially increasing noise after 10-15 years. Annual servicing helps identify and address issues before they become problems.
The Bottom Line
Heat pump noise is manageable, regulated, and rarely the issue people fear. Modern units at 40-50 dB are comparable to everyday appliances. With proper placement, basic acoustic measures, and a quality installation, most homeowners quickly forget the outdoor unit is there.
The key is working with an experienced MCS-certified installer who understands noise regulations and designs the installation accordingly. Don't be afraid to ask about noise during the quotation process—any good installer will address it proactively.
If noise sensitivity is a major concern, consider ground source heat pumps, which eliminate outdoor unit noise entirely. The higher upfront cost may be worthwhile for the peace of mind it provides.
For the vast majority of British homes, air source heat pumps are quiet, unobtrusive, and easily compliant with planning requirements. The noise concern, while understandable, is rarely the barrier to installation that people expect.