The efficiency of air source heat pumps for space heating has increased significantly in the last few years. Newly produced air source heat pumps can provide space heating from outdoor air at temperature as low as -20°C. As a result they could be utilized during most days of the year even in the cold Nordic climates.
The aim of the study described here is to analyze the impact of air source heat pumps on the Swedish energy system. The study compares the use of air source heat pumps with other commercially available heating technologies and analyzes the impacts on primary energy use using a LCA perspective. It also compares the amount of purchased energy in the detached houses, the impact on electricity production and the heating costs for house owners.
Air source heat pumps have a drawback. Their energy efficiency reduces has the outdoor air becomes colder, resulting in lower heat supply in times when it is most needed. Despite its inverse relationship between efficiency and outdoor temperature, air source heat pumps were installed in 57000 detached houses in Sweden during 2010 alone, which is 3% of the total detached houses stock. That makes air source heat pumps the most sold heating technology for detached houses in Sweden during 2010: 1.6 times more than the number of installations of ground source heat pump and 3 times more than the number of connections to district heating during the same year. Similar trends can be found in other Nordic countries.
The results show that although air source heat pumps can reduce electricity use if they replace heat generated by electrical resistance heaters, they do not reduce the electricity peak load demand, which may result in higher costs of electricity production. Air source heat pumps were not found to be the most energy efficient alternative and do not give the lowest use of purchased energy. They may even increase electricity use, electricity peak load demand and resource usage if they are used in parallel to or instead of other technologies as district heating and pellets boilers. However in a life time perspective including investment costs they are much more cost effective for house owners in comparison to more energy efficient commercial technologies, which explain their fast growing market in Nordic countries.
The conclusion from this study is that air source heat pumps will continue to be the most dominant heating technology sold under the current conditions although it does not provide the most energy efficient solution and may even increase electricity peak load demand.