Heat pump hot water systems are dead simple in theory. You start with a reverse cycle air conditioner running in reverse (heating mode). You use the heat it generates out to heat-up a well insulated tank of water. That’s it!
However in practice, heat pump hot water systems are relatively complex, with a lot of moving parts compared to a simple electric, gas or solar-panel based hot water system. This isn’t necessarily a problem, it just means that they need a bit more care and more frequent maintenance. So if you are going for a heat pump, and there are many good reasons to do so, then be sure to choose a good quality brand with an Australian presence.
Here’s a diagram that shows how everything is put together to make a heat pump hot water system:
Many folks will argue the toss over whether a heat pump is a ‘solar hot water system’ or an ‘electric hot water system’. That’s because a heat pump uses heat that is already in the surrounding air and ‘pumps’ it into the water. This heat’s original source is the sun. That’s one-nil to the solar camp. But a heat pump uses electricity to capture that heat. Hmm, that makes it 1-1. How about we compromise and call it ‘solar powered with an electric boost’. Good. That’s that settled!
The best thing about a heat pump is that it is about 5 times more efficient than a conventional electric heater. In fact the wonderful CSIRO have worked out that in many parts of Australia it can use less electricity than a solar panel hot water system with an electric boost.
Here are the advantages of a heat pump system:
- You don’t need to install anything on your roof.
- It works in all weather.
- You can run them any time – so you can take advantage of off peak electricity prices
- If you have solar electricity, they are an excellent way to use the excess production instead of selling the solar electricity back to the grid for a pittance.
But here are the disadvantages:
- Just like an air con unit, they can be noisy.
- They work most efficiently in warmer climate zones.
- They can use ozone-depleting CFCs
- They are pretty expensive ($3,000+) Almost as much as a conventional solar hot water system.