Heat pump water heating
Heat pumps are now a popular means of heating New Zealand homes and offices. The same technology can also be used to heat water. In most cases, heat pump water heaters will use less energy than conventional heating, produce fewer greenhouse gas emissions and save you money.
Why choose a heat pump water heater?
Heat pump water heaters use about half the electricity that a conventional electric hot water tank does.
They can work well in places that aren’t good for solar water heaters – places that get less sun like the south side of hills.
Heat pump water heaters can be installed in both new and existing buildings.
Saving money with heat pump water heating
Heat pump water heating systems cost between $5,000 and $7,000 to buy and install, compared to $1,500 to $3000 for a traditional electric hot water tank. But the average home of four people would save around $400 a year on electricity bills using a heat pump water heater compared to the electric hot water tank. [1]
How heat pump water heaters work
A refrigerator moves heat from inside the fridge to the outside – keeping the inside cold. A heat pump heater uses the same principle in reverse. It transfers heat from outside into a hot water tank.
The outside air gets heated up by energy from the sun every day of the year. So even when the sun is not shining brightly, or it is the middle of winter, there is still a lot of solar heat energy available to use.
Heat pump systems only use electrical energy to ‘move’ the heat - they don’t actually ‘make’ heat. This makes heat pump systems much more efficient than traditional electric or gas heaters. The actual efficiency that you would get from a HPWH depends on the make of the heat pump, the average temperatures where you live and the location of the outdoor compressor unit.
Things to consider when buying a heat pump water heater
Types of heat pump water heaters
There are two different types of heat pump water heater: split systems and all-in-one units.
Split systems have the compressor unit outside and the hot water tank inside the house. In some cases you can use your existing tank.
All-in-one units have the compressor and tank together and the whole system usually sits outside.
Optimal conditions for heat pumps
Generally, the hotter the outside air, the better the heat pump runs. Heat pump water heaters tend to work best in areas with average air temperatures above about 7 degrees Celsius. But most will still run more efficiently than a traditional electric heater in below-zero temperatures.
If you live in a colder part of the country, ask your manufacturer if their system is designed to work at low temperatures. Ask to see performance results at different temperatures for the model you are thinking of buying.
Other uses for heat pump water heaters
Some heat pump water heating systems can also give you ‘central heating’. They do this by pumping warm water from the hot water tank around a system of under-floor heating pipes.
Some other systems can be used to heat a hot tub, spa or swimming pool more cheaply than using an electric heater.
Consent requirements
You are likely to need a building consent to install a heat pump water heater. Check with your regional, district or city council.
Consumer NZ heat pump water heating report
In April 2009 Consumer NZ (with the support of EECA) carried out tests on the performance of six heat pump water heaters suitable for household use.
The complete report can be accessed free of charge from the Consumer NZ website.
More information
- ENERGYWISE™ funding for heat pump water heaters
- Heat pump and solar water heating funding for public buildings
- Solar water heating
- Choose the right water heating system
Notes
[1] Estimates are based on: a ‘typical’ household of 4 people using a standard electric 180 litre tank for heating hot water. Savings are calculated at 18.5 c/kwh.
