Glossary of Terms

When you are talking to salespeople or looking at the literature, you may feel inundated with acronyms and technical vocabulary. This section is meant to be a reference when you encounter these terms and may provide guidance on what values are appropriate for homes in Waterloo Region. The terms are grouped into those that deal with total heating capacity, those that deal with energy efficiency, the terms that deal with other characteristics of heat pumps, and finally a section for terms related to heat pump water heaters.

The first hour rating is the volume of hot water that a full, heated tank can supply in the first hour. A household where all occupants shower in the morning will require a tank with a larger first hour rating than a household where occupants shower at intervals that allow the tank to heat new water. Heat pump water heaters tend to have lower first hour ratings because, although they heat water efficiently, they do so much slower than conventional systems. For this reason, many systems are hybrid: using an electric resistance heater to heat the water when demand is high and the heat pump only when demand is low.

Energy factor (EF) is the amount of heating/cooling that a home requires to maintain the desired temperature. This value is needed to determine the correct size of the heat pump: too small and it will not supply all of the heating/cooling required and too big and the system will be less energy efficient. The load is affected by the insulation levels in the home, how airtight the building is, its size and the local climate. Your contractor should do a heat loss calculation based on the actual or modeled heat load of the home. The heating/cooling load is reported as Btu.

Uniform energy factor (UEF) is an energy efficiency factor that standardises the test methods across water heater bins (bins are based on size and first hour rating). Higher UEF values reflect greater energy efficiency.

Coefficient of performance (COP) is the ratio of the heat energy added to the water to the electrical energy drawn by the heat pump water heater. Heat pumps are tremendously energy efficient because they are moving heat, not generating heat: COP values of 3-4 (300%-400% efficient) are common.

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