Heating seasonal performance factor (HSPF) is a term used in the heating and cooling industry. HSPF is specifically used to measure the efficiency of air source heat pumps.
The higher the HSPF rating of a unit, the more energy efficient it is. An electrical resistance heater, which is not considered efficient, has an HSPF of 3.41.
The HSPF is related to the non-dimensional Coefficient of Performance (COP) for a heat pump, which measures the ratio of heat energy delivered to electrical energy supplied, independently of the units used to measure energy. The HSPF can be converted to a seasonally-averaged COP by converting both the BTU heat output and the electrical input to a common energy unit (e.g. joules). Since 1 BTU = 1055.056 J, and 1 watt-hour = 3600 J, the seasonally-averaged COP is given by:
Avg COP = Heat transferred / electrical energy supplied = (HSPF * 1055.056 J/BTU) / (3600 J/watt-hour) = 0.29307111 HSPF.
For instance, a system which delivers an HSPF of 7.7 will transfer 2.25 times as much heat as electricity consumed over a season. In Europe the term Seasonal Performance Factor ("SPF") is used to mean the same as the average COP over the heating season. A system which transfers 2.25 times as much heat as the electricity consumed is said to have an SPF of 2.25. A well designed ground source heat pump installation should achieve an SPF of 3.5, or over 5 if linked to a solar-assisted thermal bank.
Example: For a heat pump delivering 120,000,000 BTU during the season, when consuming 15,000 kWh, the HSPF can be calculated as :
- HSPF = 120000000 (BTU) / (1000) / 15000 (kWh)
- HSPF = 8
- "Springfield, Illinois City, Water, Light & Power - Appliance Efficiency Ratings". Archived from the original on 2011-10-06. CS1 maint: discouraged parameter (link)
- "ANSI/AHRI 210/240-2008: 2008 Standard for Performance Rating of Unitary Air-Conditioning & Air-Source Heat Pump Equipment" (PDF). Air Conditioning, Heating and Refrigeration Institute. 2008.
- "Residential Compliance Manual for the 2016 Building Energy Efficiency Standards". Energy Code Ace. California Energy Commission. §8.6.2.
- "Federal Tax Credits for Energy Efficiency".
- 7.7 times 0.293 is 2.25. Alternatively, 7.7 divided by 3.41 is 2.25
- Thermalbanks and Thermal Energy Storage, http://www.icax.co.uk/Seasonal_Performance_Factor.html