Energy efficiency is vital when talking about Heat Pumps but there are many other important aspects that effect its performance and these are highlighted in this response. The key aspects identified, include sound, cold temperature operation & defrost function, servicing and delivery load.

What aspects of heat pump water heater performance (in addition to energy efficiency) do you think are important (e.g reheat time, noise, ability to operate in a range of climates, service life and others)?

The following are the primary features of a well designed Heat Pump Water Heater and all need to be weighted to achieve an optimum system.

A. System durability, factors such as tank material and compressor quality are paramount. STC’s are based on a unit performing for 10 years and therefore the standard warranty and durability should reflect this with the unit delivering hot water consistently for this period.

B. Load delivery, which incorporates a balance between Tank Volume and Recovery Rates. Understanding the importance of an immersed coil compared with a wraparound coil. It is paramount to energy saving that units do not store excessive amounts of unused hot water. The right model needs to be available for the right home.

C. Noise and impact on the household can be reduced either by incorporating acoustics into the design process, i.e centrifugal fans or through the use of timers to reduce noise pollution during night time hours (reliant on the correct tariff & usage patterns).

D. Defrost function, cold weather operation is important as most heat pumps installed in even moderate climates will regularly be subjected to ambient conditions below coil freezing points, i.e less than 10C for most models. To avoid damage to systems or extended heat up times, all systems should incorporate some cold temperature functionality.

E. Service ability, Heat Pumps should have clear service structures, use refrigerants available to most refrigerant mechanics and ensure that there is adequate access for servicing to be undertaken.

By Simon Baird

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