 Although air source heat pumps are less efficient than well-installed ground source heat pumps in cold conditions, air source heat pumps have lower initial costs and may be the most economic or practical choice.A study by Natural Resources Canada found that cold climate air source heat pumps (CC-ASHPs) do work in Canadian winters, based on testing in Ottawa, Ontario in late December 2012 to early January 2013 using a ducted CC-ASHP.