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Departments/Research By Andrew Pollard, BRANZ Building Physicist
The low-down on heat pumps
Heat pumps are now commonplace in New Zealand homes. People are happy with their purchase, but BRANZ research shows they aren’t being operated to perform as well as they might.
BRANZ HAS RECENTLY concluded a study of how people use heat pumps in their homes. The study examined 160 households from around the country with heat pumps and assessed how they were installed, what the occupants thought of them and how they used them. Measurements were also made of how much energy the heat pumps used, as well as the resulting indoor conditions from their use.
Heat pumps in half of new homes
It is remarkable how quickly heat pumps have become an accepted part of the way we heat our homes.
The BRANZ Household Energy End-use Project (HEEP) was a large-scale project looking at how we use energy in our homes. When HEEP nished collecting data around 10 years ago, only 4% of households had heat pumps. In fact, these devices weren’t even called heat pumps but reverse-cycle air conditioners.
Today, heat pumps are very popular, with over half of new homes including at least one.
Most happy to recommend
People who examine the uptake of new technologies talk about bridging the chasm between the small numbers of early adopters and the majority that eventually take up that technology. A sign that the chasm has been breached is that discussions of the technology move into general conversations and change from being of a technical nature to one of social acceptance.
Householders interviewed as part of the heat pump study frequently stated that seeing others purchasing heat pumps motivated them to also purchase one. TV advertisements featuring heat pumps are now common and frequently include sporting stars endorsing particular models. A web search of ‘heat pumps in New Zealand’ provides an occasional link to EECA or Consumer but also a deluge of information from retailers, suppliers and installers recommending a particular brand.
The householders taking part in the heat pumps study were very happy with their heat pumps, with over 94% willing to recommend heat pumps to friends and family.
Heat pumps have changed heating patterns
An important nding in the heat pumps project was that heating behaviours are changing. HEEP found that over one-third of house- holds used heaters in the morning, while in the heat pumps project, those using heat pumps leapt to over 85% of households.
The relative percentage change for 24-hour heating is even greater, with over a quarter of houses with heat pumps reporting that they are left on continuously. For general heating, HEEP found that just over 10% of houses had 24-hour heating (see Figure 1).
E ciency drops with temperature
Heat pumps are advertised as an e cient means of heating, but there is very little information about how they work in practice. Heat pump models can have high laboratory e ciency levels. These
76 — February/March 2016 — Build 152