The heating and cooling efficiencies of residential heat pumps are often characterized bya single number for each mode. These values are determined at specific test conditions. Forheating, this rating is referred to as the HSPF (Heating Seasonal Performance Factor), and forcooling (for both heat pumps and air conditioners) the rating is the SEER (Seasonal EnergyEfficiency Ratio). These values are used by consumers to compare conditioning systems, byutility program managers and regulators to predict savings and establish incentives, and bydesigners to specify equipment.The seasonal performance factors are also often used to predict annual energy use andpotential savings from equipment upgrades. However, the actual performance of the equipmentdepends on a variety of factors, including the climate in which it is being used and the heat lossrate of the building. Furthermore, the overall energy use (and seasonal performance) can begreatly impacted by factors such as equipment sizing, control strategy, and duct losses.This paper presents the results of a review of the industry standard HSPF calculationprocedure. This review included consideration of the impacts of climate and building load on theactual seasonal performance, as well as an investigation into the standard algorithm itself. Thisinvestigation found several inconsistencies between the standard and actual heat pump andbuilding performance, such as the calculation of building load, the generation of heat pumpperformance data, and the use of defrost. The results show that the HSPF rating is inappropriatefor many locations, and thus can not be used to estimate energy use or savings. They also showthat the calculations can be significantly impacted by the method in which the building load iscalculated, as well as by the performance data and degradation coefficients used.
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