The noise produced by heat pumps is a much-discussed topic, both technically and legally. In this blog, we outline the key points of attention regarding the noise levels of heat pumps. Where does the noise from a heat pump come from? What do laws and regulations say? And how can noise nuisance be minimized during installation?
Where does the noise from a heat pump come from?
The noise produced by heat pumps is a frequent topic of discussion in practice. Understandably so, because an incorrectly installed heat pump can lead to nuisance or complaints. But where exactly does the noise in a heat pump come from? For an air-to-water heat pump, the main noise sources are:
- Fan (outdoor unit) The fan draws in outdoor air, which comes into contact with the refrigerant in the heat exchanger where heat generation takes place. Fans are generally the largest source of noise.
- Compressor (outdoor and indoor unit) The compressor raises the temperature of the refrigerant to hot gas. In newer heat pump models, the compressor compartment is well sound-insulated. In addition, inverter-controlled compressors regulate output to lower levels at certain times. This allows the fan to run at a lower speed, reducing noise.
Vibrations and resonance
Noise can be amplified when a unit is mounted on roofs or walls, where it may resonate with façades or supporting structures. This can create a “sound box” effect, converting vibrations into a low humming noise.
What do laws and regulations say about heat pump noise?
Since 1 April 2021, national noise limits apply to outdoor units of heat pumps. For apartments and/or multiple residential units on the same plot, these can be summarized as follows:
- Maximum 45 dB(A) between 7:00 a.m. and 7:00 p.m. at the property boundary or at openable windows or doors of dwellings.
- Maximum 40 dB(A) between 7:00 p.m. and 7:00 a.m. at the property boundary or at openable windows or doors of dwellings.
For reference, 40 dB(A) is comparable to soft murmuring or the sound of a refrigerator. Always check the local zoning plan during installation; in some cases, such as hospitals, stricter noise requirements may apply.
Measuring heat pump noise
Noise can be measured in different ways. Many misunderstandings arise because sound power level (LwA) and sound pressure level (LpA) are confused. Sound power level (LwA) is the sound energy emitted by the source itself (manufacturer’s specification). Sound pressure level (LpA) is the sound audible to humans at a specific distance, such as 1, 5, or 10 meters from the unit. A noise assessment for a heat pump requires great precision. We recommend having measurements carried out by a specialist.
Why correct placement and installation are crucial
The installation and positioning of a heat pump have a major impact on both noise levels and performance. In practice, complaints about noise are rarely caused by the heat pump itself, but almost always by incorrect positioning, mounting, or sizing.
An incorrectly installed heat pump can lead to:
- Noise nuisance and complaints from neighbors
- Exceeding the legal noise limits (40 or 45 dB(A))
- Reduced efficiency (lower COP)
- Vibrations and resonance in façades or structural elements
- Legal disputes and corrective work afterwards
What should you consider when installing a heat pump?
Proper placement prevents noise issues and increases the reliability and lifespan of both the heating system and the heat pump. During installation, keep the following points in mind:
- Location of the outdoor unit
The best place for a low-noise heat pump is on the ground, preferably on a concrete foundation with sufficient distance from façades, corners, and property boundaries. Heat pumps are also often installed on roofs. In that case, it is important that the unit is supported at points with sufficient load-bearing capacity and mass to dampen vibrations. Installing a heat pump in the middle of a roof section is discouraged, as the roof structure may act as a sound box.
- Vibration and resonance control
Vibrations significantly increase noise production. Always use vibration dampers (preferably rubber dampers) and avoid rigid mounting in the middle of a roof section. Even a technically quiet heat pump can be perceived as highly disruptive due to resonance in the roof structure.
- Airflow and thermal performance
For proper operation, the heat pump must be able to freely draw in and discharge air. Ensure sufficient clearance around the unit and take into account snow accumulation and falling leaves in autumn. Restricted airflow can lead to lower efficiency, higher fan speeds, increased noise, and more wear.
- System sizing and noise production
Oversizing is a common mistake. Heat pumps that are too large operate more often at part load and switch on and off more frequently. This increases noise levels and reduces efficiency and service life. Therefore, match the capacity to the actual heat demand rather than the capacity of an old boiler. Correct sizing results in a quieter, more efficient and more stable system. And it requires a lower investment.
- Night mode and noise reduction settings
Many modern heat pumps are equipped with night mode, noise reduction modes, and time-controlled power limitation. Activate these functions during commissioning. Clearly explain their operation to the user and document the settings in the handover report. A reduction of 3 dB(A) is perceived as a halving of the noise level.
- Communicating with the customer in advance
Good communication helps prevent complaints. Discuss the expected noise level, placement options and alternatives, noise-reducing measures, and applicable laws and regulations in advance. A well-informed customer is less likely to experience nuisance.
Conclusion: placement is at least as important as the heat pump’s noise level
Noise production is an important consideration for heat pumps, but it is not an unsolvable problem. With a quiet model, correct placement, and professional installation, noise standards can almost always be met. This keeps disturbance to a minimum and ensures the heat pump operates as efficiently as possible.
Would you like to learn more about the noise performance of our heat pumps? Feel free to contact us or visit our factory. We have a heat pump on display that you can see and hear for yourself, so you can experience how much noise the unit produces.
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