Heating Seasonal Performance Factor (HSPF) & Kilo-Watt per Ton (kW/ton)

Heating Seasonal Performance Factor (HSPF)

This is a measurement of the efficiency of a system and the units are the same (BTU/h divided by Watt). However, this measures the efficiency of the system in heating mode, not cooling mode. Therefore it applies only to heat pumps or reversible air conditioning units and not to units that only cool a space. A variant of equation 7 applies:

As with COP, EER, and SEER, the higher the number of HSPF the greater the efficiency.
In the US, the DoE specifies the minimum values for HSPF as shown in table 3. The law was changed in January 2006 and the table lists the old and new standards.
For example, Assume a system has an HSPF of 8. Then from equation 16, the COP is 2.3. This means that 2.3 times the amount of heat is put into the space than is consumed in electricity. Put another way, for every 1 kWh of electrical energy used by the heat pump, 2.3 kWh of heat energy is input to the space.

Kilo-Watt per Ton (kW/ton)

The efficiencies of large industrial air conditioner systems, especially chillers, are given in kW/ton to specify the amount of electrical power that is required for a certain power of cooling. In this case, a smaller value represents a more efficient system. However, as we have seen, to be valid, this number must be reported at various operating conditions, especially the indoor and outdoor temperatures, and the difference between chilled water return and chilled water supply.
You can convert kW/ton to COP as follows:

Because a ton of refrigeration is equivalent to 3.517 kW.