What unit is used to rate heat pump mode efficiency?

The rating used to assess the efficiency of a heat pump in heating mode is the Heating Season Performance Factor (HSPF). HSPF measures the amount of heating provided by a heat pump in British Thermal Units (BTUs) compared to the amount of electricity consumed in watt-hours during the heating season. A higher HSPF indicates a more efficient heat pump, which is beneficial for energy consumption and cost-effectiveness.

In contrast, Seasonal Energy Efficiency Ratio (SEER) is used to rate cooling efficiency, while the Energy Efficiency Ratio (EER) is a measure of efficiency at a specific operating condition, typically used for air conditioners. Annual Fuel Utilization Efficiency (AFUE) is specific to heating systems that utilize fuel, such as furnaces, and measures how efficiently the energy in the fuel is converted to heat.