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 pump
An air source heat pump (ASHP) is a heat pump that can absorb heat from air outside a building and release it inside; it uses the same vapor-compression refrigeration process and much the same equipment as an air conditioner, but in the oppos ...
s.
HSPF is defined as the ratio of heat output (measured in
BTUs) over the heating season to electricity used (measured in
watt-hour
A kilowatt-hour ( unit symbol: kW⋅h or kW h; commonly written as kWh) is a non-SI unit of energy equal to 3.6 megajoules (MJ) in SI units, which is the energy delivered by one kilowatt of power for one hour. Kilowatt-hours are a commo ...
s).
It therefore has units of BTU/watt-hr.
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.
Depending on the system, an HSPF ≥ 9 can be considered high efficiency and worthy of a US energy tax credit.
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.
[7.7 times 0.293 is 2.25. Alternatively, 7.7 divided by 3.41 is 2.25] 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.
[Thermalbanks and Thermal Energy Storage, http://www.icax.co.uk/Seasonal_Performance_Factor.html]
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
The HSPF is related to the non-dimensional
coefficient of performance
The coefficient of performance or COP (sometimes CP or CoP) of a heat pump, refrigerator or air conditioning system is a ratio of useful heating or cooling provided to work (energy) required. Higher COPs equate to higher efficiency, lower energy ( ...
(COP) for a heat pump, which measures the ratio of heat delivered to work done by the compressor. The HSPF can be converted to a seasonally-averaged COP assuming a lossless compressor and no heat loss by multiplying by the heat/energy equivalence factor .29307111 W·h per BTU. HSPF, which is normally measured rather than calculated, is reduced by losses due to such things as electrical resistance in the motor and thermal resistance in the evaporator.
See also
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Coefficient of performance
The coefficient of performance or COP (sometimes CP or CoP) of a heat pump, refrigerator or air conditioning system is a ratio of useful heating or cooling provided to work (energy) required. Higher COPs equate to higher efficiency, lower energy ( ...
*
Heat pump
A heat pump is a device that uses electricity to transfer heat from a colder place to a warmer place. Specifically, the heat pump transfers thermal energy using a heat pump and refrigeration cycle, cooling the cool space and warming the warm s ...
*
SEER
References
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Energy conservation
Heating, ventilation, and air conditioning