Combined U.S. factory shipments of central air conditioners and air-source heat pumps for December totaled 330,698, a 16 percent drop compared with December 2006 totals, according to the Air-Conditioning, Heating and Refrigeration Institute (AHRI).

Combined U.S. factory shipments totaled 6.4 million in 2007, down 9 percent from the previous year. See chart of combined shipments for Jan. 2005 through Dec. 2007.

Heat pump shipments for December totaled 115,556, down 14 percent compared with December 2006 shipments. For the year, heat pump shipments totaled 1.9 million, down 10 percent from 2006.