A new simplified procedure to calculate the heating seasonal performance factor (HSPF) of surface water heat pump (SWHP) systems was proposed in this paper, based on the energy consumption analysis and the temperature frequency method. This method permits one to evaluate heating energy requirement of buildings by a calculation with daily average water temperatures and outdoor air temperatures, thus the best heating mode of a SWHP system is suggested. Besides, based on the daily energy consumption comparison between SWHP system and air source heat pump (ASHP) system, it was concluded that SWHP can save 31.5% of the energy consumption, which indicated the SWHPs are superior to the ASHPs evidently in the energy saving respect.