Air Conditioning, Heating, Refrigeration News, May 26, 2014, by Matt Bishop.
http://www.achrnews.com/articles/126688-heat-pumps-riding-a-wave-of-popularity

"According to the Air-Conditioning, Heating, and Refrigeration Institute (AHRI), shipments of equipment increased in just about every category in 2013. Especially notable were shipments of air-source heat pumps, which were up 16 percent over 2012.

That good news has spilled over into this year as well, with a recent AHRI report showing a 25.4 percent year-to-date increase in air-source heat pump shipments for the first two months of 2014. With heat pumps becoming more popular across the U.S., manufacturers expect sales to remain strong for quite a while."