Researchers from ETH Zurich have conducted the largest field study to determine whether heat pumps are running efficiently. When examined in operation, these units are often not optimally configured. Monitoring systems and legal standards could provide a remedy.
Heat pumps are currently the most sought-after heat source in Switzerland. Their number has increased many times since 2000, and every fifth building is now heated with one. These units make an essential contribution to society’s net-zero target.
However, they increase electricity consumption, making their efficient operation an important consideration. Most owners cannot tell whether their units have been properly configured. This is why trust in and acceptance of the deployment of climate-friendly technologies depend on their efficiency, which is directly reflected in energy bills.
Europe-wide field study
In the largest and most extensive study to date, researchers at ETH Zurich investigated the efficient operation of heat pumps. They spent two years gathering real-time data from 1,023 units in ten European countries, including Germany, Austria, the Netherlands, Sweden, Denmark, France, and the United Kingdom.
The study aimed to develop a system to compare the units in a standardised manner, even though they were installed in different types of buildings. The study’s authors only had access to data from one manufacturer, but they assume that their findings will also apply to others.
“Our results can be interpreted universally, as the collected data and algorithms are based exclusively on physical measurements such as flow temperature and energy consumption,” said Tobias Brudermüller, one of the main authors.
Incorrect configurations lead to energy wastage
During the observation period, considerable differences in performance emerged. In some cases, the units with the lowest efficiency levels were two or three times less efficient than those with the highest. 17 per cent of air-source heat pumps fell short of the European efficiency standards.
They determined that optimising the heating curve setting would solve this problem for many units. The ETH researchers also showed that one unit in ten was too large in their study. A less powerful unit would have sufficed for the prevailing conditions in the building and would have consumed less electricity. However, only 1 per cent of units were too small, which can lead to units becoming overworked and breaking down more readily.
“Even though we knew that errors in planning and configuring heat pumps were not uncommon, it surprised us how strongly this was reflected in the actual efficiency levels achieved, and how clearly that showed up in the data,” said Thorsten Staake, Co-Chair of the Bits to Energy Lab at ETH Zurich.
Heat pumps in Switzerland could be more efficient
In 2023, Tobias Brudermüller carried out similar studies in Switzerland in collaboration with industry partners, the Swiss Federal Office of Energy, and the electricity utility provider of the canton of Zurich (EKZ). These were based on electricity consumption data from Swiss households equipped with smart meters and evaluated using artificial intelligence.
These studies determined that 41 per cent of the 410 units under investigation had their heating curve set too high, so the heat pumps had to generate an unnecessarily high rise in temperature. In 36 per cent of cases, the reduced-temperature night mode was activated, which led to the building cooling overnight and then requiring reheating in the morning. In 26 per cent of cases, the heat threshold was set too high, meaning that the units were in operation for longer than necessary in light of the outdoor temperature.
Digital tools needed
The study’s authors suggest standardising the monitoring of the units across Europe to guarantee efficiency over the entire life cycle. “We still do not have the framework conditions for technical standards that would suit the variety of situations affecting real-life buildings,” said Brudermüller.
By developing their algorithms, they want to inform households specifically about the potential for optimising their heat pumps. Sensor data from web-enabled heating appliances and smart meters opens up new possibilities.
“This data will help owners get to know their units better, reduce their energy bills, and improve satisfaction with their units. That will lead to these systems catching on more quickly and climate targets being reached sooner,” said Brudermüller.
Elgar Fleisch added, “Heat pumps are already an advanced technology for climate-friendly heating. The next step is to make their operation more intelligent and efficient. Our field studies create the basis for quickly bringing this innovation into households and making its mark directly through lower energy bills.”
