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.
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 a measure of the system’s efficiency, with higher values being more efficient. It takes into account the efficiency of heating the water, the standby losses (lack of insulation), and losses from water circulating through the tanks and inlet/outlet pipes.
Uniform energy factor (UEF) is an energy efficiency factor that standardizes 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.