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Air or Ground: the two types of heat pump

Heat pumps are fairly new technology in New Zealand. We’ve only started using these types of heating system in our homes within the last few decades and we’re still learning about the way they work.

For most of us, the term heat pump denotes a piece of equipment on the wall of a home that delivers warm air to the inhabitants indoors. However, there is another type of heat pump on the market – the ground source heat pump. This is built on the same principle but draws its heat from an entirely different place.

Just as air source heat pumps gather heat from the ambient atmosphere and direct it indoors, so do ground source heat pumps derive their heat from the earth. The concept is identical – scoop up the free heat that’s out there and deliver it indoors where humans can get the benefit of it.

The technology is tried and tested. With both types of heat pump, a heat exchanger concentrates the warm molecules of air entering the system and exchanges them for cooler ones from indoors. Think of it as an air conditioner in reverse.

The main difference comes in the cost of heat pump installation.
A ground source heat pump utilises pipes that are buried several feet underground, while an air source heat pump simply needs access to the outside atmosphere. For obvious reasons, it is much more expensive to excavate an underground system than simply install a heat pump on the external walls of your house. The cost of labour and materials is much greater.

Cost is the bottom line

But there is one intriguing extra factor. If your home is in a geothermal area, the logic of using free heat from Mother Earth may be overwhelming.

If you live in the central North Island, it may be worth investigating the economics of a ground source heat pump. You will still need to bear the cost of excavating a large area outside your house and installing pipes and a heat exchanger system. But once your ground source heat pump is installed you’ll enjoy copious heat at a low running cost.

If you don’t live in Rotorua, don’t worry. You can still install a very efficient air source heat pump to deliver year-round heat at a very affordable cost. And you won’t have to put up with the aroma of rotten eggs every day.