So a heat pump with an HSPF rating of 9 is 23 percent more energy efficient than one with an HSPF rating of 8.2, because 263 percent (the percentage of efficiency for an HSFP 9 heat pump) minus ...

These new metrics are SEER2, EER2, and HSPF2, and as noted, their ratings will be reduced compared to the 2023 SEER, EER, and HSPF minimum efficiency ratings for each region. For instance, the ...