Dutch utility Eneco is testing low-noise air-to-water heat pumps from startup Whspr in around 20 homes, aiming to ease installation constraints near property boundaries. The systems reportedly achieve coefficients of performance of up to 5 and show up to 80% noise reduction in laboratory testing.

Dutch utility Eneco has begun testing an”innovative” type of air-to-water heat pump with low sound levels in residential buildings.

The company said conventional heat pumps rely on outdoor units that emit a constant hum, requiring installations several metres from property boundaries under Dutch building regulations and often forcing placement in prominent locations on terraced houses. By contrast, the “silent” heat pumps under test can be installed just 30 cm from the boundary.

“The pilot will provide insight into both ease of installation and real-world performance,” Eneco said in a statement. “The results will be used to further optimize the system, with the aim of making it widely available by the end of the summer.” The company added that around 20 homes are currently equipped with the systems to assess noise levels without “compromising residents’ everyday heating comfort.”

The heat pumps are supplied by Dutch startup Whspr. “Our 4 kW freestanding hybrid monoblock systems are designed for domestic space heating,” founder Hugo Huis in ’t Veld told pv magazine.

The unit measures 60 cm × 60 cm × 90 cm and weighs around 70 kg. “It is compact yet robust,” Huis in ’t Veld said, adding that initial measurements show efficiencies in line with the market, with coefficients of performance (COP) of between 4.5 and 5.0.

According to the manufacturer, the heat pump uses propane (R290) as its refrigerant and shows up to 80% noise reduction in laboratory testing.

Whspr also highlights ease of installation, stating that a single installer can fit and connect the unit, including the water side, in one day. A dedicated control and thermostat system has also been developed to reduce compatibility issues and simplify commissioning.

Further technical details have not yet been disclosed. “We are not at liberty to share designs at this stage, as patents are still pending,” Huis in ’t Veld said.

Eneco noted that pilot installations include both standard locations and more complex sites, such as rooftops and sheds at the end of gardens. The systems have also been installed in several rental homes owned by housing association Wooncompagnie. “Testing will continue until the end of April, after which the heat pumps will be further optimized,” the company said.