It's a question we get asked at almost every site visit, and almost never before a quote is already in hand: where is the outdoor unit actually allowed to go, and what happens if the neighbour complains? Unlike air conditioning, an air-to-water heat pump runs all year round, often at night, exactly when noise rules are strictest.
This article lays out the legal and practical framework in French-speaking Switzerland in 2026, with the real figures we measure on our own job sites.
Why heat pumps raise a different problem than air conditioning
Air conditioning mainly runs in summer, during the day or evening, in the time windows with the least strict noise limits. An air-to-water heat pump, by contrast, heats the home and often the domestic hot water year-round, with an activity peak in winter — precisely when nights are longest and night-time noise limits are most restrictive.
Technically, an air-to-water heat pump extracts heat from outdoor air that's often close to 0°C, which puts more strain on the compressor than air conditioning, which simply rejects heat into air that's already warm. On top of that come periodic defrost cycles, more audible in cold, humid weather as frost builds up on the heat exchanger.
The result: at comparable rated output, an air-to-water heat pump typically sits at 55 to 65 dB(A) sound power, versus 48 to 55 dB(A) for a residential air conditioner. That's not a manufacturing flaw — it's simply the physics of winter heating demand.
The legal framework: the noise ordinance, day and night
Switzerland's noise protection ordinance (OPB) sets limit values by planning zone, with a strict day/night distinction.
| Zone | Day (6am-10pm) | Night (10pm-6am) |
|---|---|---|
| Quiet residential zone (DS II) | 60 dB(A) | 50 dB(A) |
| Mixed zone (DS III) | 65 dB(A) | 55 dB(A) |
| Commercial zone (DS IV) | 70 dB(A) | 60 dB(A) |
These values apply at the property line, not at the unit itself. A heat pump rated at 60 dB(A) sound power at the source produces only 35 to 42 dB(A) at 5 metres, and less beyond that — sound dissipates quickly with distance and obstacles (hedge, low wall, façade).
The real point of attention, then, isn't the manufacturer's spec sheet, but calculating the perceived level exactly where the nearest neighbour lives, at night, under the worst-case weather conditions (severe cold, high load).
Distance and placement: what solves 90% of situations
Placement matters more than the model chosen.
Distance to the nearest occupied neighbouring window. Minimum recommendation: 3 metres. Below that, even a heat pump marketed as quiet can create a noticeable disturbance at night, especially in a bedroom.
Distance to the property line. 4 to 6 metres is generally enough, with a correctly sized heat pump, to meet night-time noise limits without extra equipment. On a narrow plot, this distance sometimes isn't achievable — that's when an acoustic enclosure or a certified quiet model becomes necessary.
Air flow orientation. As with air conditioning, directing the air outlet and fan away from the neighbouring façade noticeably reduces the noise perceived on the other side.
Mounting and vibration. A poorly chosen anti-vibration mount transmits vibration into the building structure, perceived as a hum inside homes — including in an adjoining neighbour's unit. This is a frequent, often overlooked, cause of complaints, distinct from airborne noise, and often neglected by less rigorous installers.
Acoustic enclosure. Reduces noise by 5 to 10 dB(A). Extra cost: CHF 1,000 to 3,000 depending on the heat pump's output, somewhat higher than for air conditioning due to the size of air-to-water outdoor units.
On our recent installations, correct sizing combined with these placement principles has prevented practically all neighbour disputes — even in dense residential neighbourhoods.
Sizing: an underestimated noise factor
An oversized heat pump cycles more frequently (repeated on/off switching), creating unpleasant noise spikes at every restart. An undersized one, conversely, runs continuously at full load in severe cold — precisely at night, during the winter peak, which maximises noise exactly when it matters most.
A proper heat-loss calculation, based on the building's actual heat loss rather than a rough per-square-metre estimate, is therefore as much an acoustic comfort issue as an energy performance one. It's a point many low-cost quotes skip by offering a standardised output rather than a calculated one.
Canton-by-canton rules
Vaud. For a standard residential air-to-water heat pump, a simple municipal notification is enough in most cases, with no formal building permit. Municipalities mainly check compliance with local building regulations and, occasionally, the visual integration of the outdoor unit.
Geneva. Stricter framework. Prior authorisation is more frequently required, particularly in dense urban areas where distances to property lines are tighter. The cantonal energy office (OCEN) can request acoustic evidence on constrained projects.
Fribourg. Pragmatic approach, similar to Vaud. Urban municipalities (Fribourg, Bulle) may pay closer attention to visual integration than rural ones.
Neuchâtel. Flexible framework, with no cantonal requirements beyond standard federal law and municipal regulations.
In all cases, a notification to the electricity grid operator is systematic for a heat pump, regardless of any noise question — a step your installer normally handles in full.
What happens if a neighbour complains
Direct conversation. In most cases, a direct exchange with the neighbour, possibly combined with an adjustment (quiet-mode schedule, reorientation), is enough to defuse the situation.
Municipal complaint and noise measurement. If disagreement persists, a complaint can be filed with the municipality or the relevant cantonal service. A sound-level measurement, taken under the worst-case conditions (night, severe cold), determines whether noise limits are exceeded.
Imposed corrections. If a breach is confirmed, the municipality can require repositioning, an acoustic enclosure, or in rare cases a restriction on night-time operation. A civil nuisance claim remains possible but stays exceptional in residential settings when the original installation was properly designed.
Our checklist before installing an air-to-water heat pump
- Calculate the building's actual heat loss to size the heat pump as precisely as possible, not as large as possible.
- Position the outdoor unit at least 3 metres from an occupied neighbouring window, and 4 to 6 metres from the property line where the plot allows it.
- Check the municipal permit regime (simple notification or authorisation) before signing a quote.
- Plan for an acoustic enclosure early if the plot is constrained, rather than discovering the need after a complaint.
- Choose an anti-vibration mount sized to the unit's mass, not a generic one.
- Inform the direct neighbour before installation, especially if the unit will be visible or close to a bedroom.
A well-designed, correctly sized and properly positioned air-to-water heat pump is no more prone to conflict than air conditioning. It's improvising on these four points — sizing, distance, mounting, informing the neighbour — that turns a comfort upgrade into a neighbour dispute.
