Field studies of the performance of variable capacity heat pump (VCHP) systems conducted in Stockton, California from 2014 through 2018 determined that VCHP systems can deliver improved cooling energy savings and improved heating energy savings (as compared to single speed systems that meet the federally required minimum efficiency ratings). However, the actual amount of VCHP energy savings is not accurately predicted by the energy efficiency ratio (EER), seasonal energy efficiency ratio (SEER), and heating seasonal performance factor (HSPF) published for these systems in industry directories of certified product performance. Therefore, the published EER, SEER and HSPF information for these systems is not suitable for use with the computer modeling methods required by the performance standards specified in Section 150.1(b) of Title 24, Part 6.
More accurate methods of rating VCHP systems utilizing a load-based and climate-specific method of performance testing are under development based on the Canadian Standards Association publication CSA EXP07, but published VCHP performance ratings that rely on these new test procedures are not yet available. For this reason, until such time as more accurate performance ratings are made available for VCHP systems, California Energy Commission staff recommends the methodology presented in this report be used with VCHP system types identified in this report. This provides these system types the opportunity for better than minimum energy efficiency credit for compliance with the performance standards based on the observed real-world performance of the technology.
