Heating seasonal performance factor (HSPF) of a federally regulated consumer product

means the total space heating required during the heating season, expressed in Btu's, divided by the total electrical energy consumed by the heat pump system during the same season, expressed in watt-hours, as determined using 10 C.F.R. section 430.23(m) (Appendix M to subpart B of part 430). The ‘HSPF used to evaluate compliance with 10 C.F.R. 430.32(c) is based on Region IV, the minimum standardized design heating requirement, and the sampling plan stated in 10 C.F.R. 429.16(a).