Newly produced air source heat pumps can provide heat energy 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 drawback of air source heat pumps is the reduction in efficiency as the outdoor air become 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 of detached houses to district heating during the same year. Similar trends can be found in other Nordic countries.This study compares the use of an air source heat pump with other existing commercial technologies in detached houses and analyzes the impacts on primary energy use, on final energy use, on electricity production and on costs benefits for house owners. It was found that converting existing electric heated Swedish detaches houses to district heating with biomass based CHP or bed-rock heat pump could reduce the use of resources, which could benefit Sweden as a society. Converting electric heated Swedish detaches houses to district heating or pellets stove could reduce power demand and level out the power demand load curve. That would benefit utilities of power supply as it could secure power supply. However cost effectiveness in one of most important drivers for house owners of detached houses to choose energy efficiency measures. For that reason house owners may most likely benefit by the installation of air-source heat pumps.