COP – (Coefficient of Performance): This number, which usually ranges between 2 and 5 (the higher the number the better), tells how much heating/cooling energy the mini-split offers for each unit of energy it consumes. Put simply, if a unit has a COP number of 3, that means that it creates three times as much heating/cooling energy as it uses to do this work. This isn’t magic. Heat pumps don’t create heat directly from the electricity they consume. Instead, they move heat around to where it is needed. “Air to Air” heat pumps, the category that mini-spits fall under, efficiently move heat from the air outside your house to inside your house (in heating mode), or from inside to outside your house (cooling mode). They can heat your house even when the air outside is much colder than the air inside. Likewise, they can cool your house even when the air outside is much hotter than inside (just like an air conditioner does).
HSPF – (Heating Seasonal Performance Factor): This number, which usually ranges from about 7 to 14 (again, the higher the better) indicates the expected heating performance of a mini-split unit over an entire season (like winter!). Obviously, your heating bill in October might be much less than your heating bill in January. So this number indicates the expected heating performance of a heat pump in different conditions over time. It is especially indicative of how well the heat pump provides heating, as opposed to the next number, SEER, which indicates how well the heat pump provides cooling.
SEER – (Seasonal Energy Efficiency Ratio): This number, which usually ranges from about 10 to 30 (again, the higher the better), is similar to the HSPF number, but is regarded as the best indicator of the cooling ability of a particular mini-split. In other words, a mini-split with a SEER number of 30 will be much more efficient than a mini-split with a SEER number of 15.
EER – There is also an acronym called “EER” which remains in wide use. It is sometimes used in product literature and is related to COP. The EER = 3.41214 × COP.