Are Heat Pumps Noisy? An Honest Answer

Modern domestic heat pumps produce 40-55 dB(A) measured at 1 metre from the unit, depending on operating conditions. At normal operating distances from a neighbour's boundary (1-2 metres), typical sound levels are 35-45 dB(A). For context, 40 dB is similar to a quiet library, 50 dB is similar to moderate rainfall. Modern heat pumps (Daikin Altherma 3, Mitsubishi Ecodan, Vaillant arotherm+) are significantly quieter than units from 5-10 years ago.

Under permitted development rights (as amended from 9 December 2023), a single air source heat pump can be installed without planning permission if it produces no more than 42 dB(A) measured 1 metre from any neighbour's window or door. This applies only when the neighbour's window/door is at a distance of at least 1 metre. If this criterion cannot be met, or if installing more than one heat pump, a full planning application is required.

Yes. Excessively noisy heat pumps can be reported to the local Environmental Health department as a statutory nuisance under the Environmental Protection Act 1990. However, a correctly installed, modern heat pump operating within its design parameters and sited appropriately rarely generates complaints. Poor installation (unit placed close to a neighbour's bedroom window, or in a corner that amplifies sound) is the most common cause of noise complaints.

Heat pumps run in cycles, similar to a refrigerator. During mild weather, the unit may run for long periods at lower speeds (inverter-driven models modulate fan and compressor speed). In cold weather, the unit runs harder and louder. Defrost cycles occur every 2-6 hours in cold, humid conditions — during a defrost, you may hear increased fan noise for 3-8 minutes as the system reverses its cycle to melt ice from the outdoor coil. This is normal and not a fault.

Louder-than-expected operation can have several causes: the unit is positioned in a corner or against a wall that reflects and amplifies sound; the base is not properly isolated from vibration; the flow temperature is set too high, causing the unit to work harder; the refrigerant charge is incorrect (requires engineer attention); or the fan or compressor is developing a fault. Contact us if your unit becomes noticeably louder than when first installed.

Professional installers use several methods: choosing a quieter model for noise-sensitive installations; positioning the unit away from windows and not in corners; using an anti-vibration mat between the unit and its base; ensuring the base is firm, level, and not directly connected to hollow structures that resonate; and adjusting the flow temperature to the minimum needed for comfort (lower temperatures mean less compressor effort and less noise).

Yes. In cold weather (below 5°C), the heat pump works harder to extract heat from cold outdoor air, running the compressor at higher speeds and producing more noise — typically 3-5 dB louder than in mild conditions. Most modern inverter-drive heat pumps manage this automatically and stay within permitted development noise limits even at low outdoor temperatures. In very cold spells (below -5°C), some units run at maximum capacity and are noticeably louder for short periods.

Yes, with appropriate model selection and siting. For properties with close neighbours, conservation areas where noise could affect character, or locations where the 42 dB limit may be challenging to achieve, we carry out a noise impact assessment and may recommend quieter premium models or specific siting strategies. In some cases, acoustic enclosures or barriers can reduce propagated sound, though these must be designed carefully to not restrict airflow.