Which systems are most efficient?

Some energy efficient hot water systems can be directly compared to others of the same fuel type thanks to the government-backed ratings standard (in particular, MEPS and gas star ratings). These ratings aren’t quite as useful for comparing between different fuel types though. For example, gas and electricity star ratings cannot be compared on an apples-to-apples basis. To break it down, here’s an easy to follow guide, ranking the available fuel types from most efficient to least.

1. Solar boosted

The most efficient systems available, solar boosted systems are generally boosted by either gas or electricity, but get most of their energy from the sun. Bear in mind that if boosted by electricity, this ranks the system below natural gas but above heat pumps in terms of operating costs and emissions.

2. Natural gas/LPG

Continuous flow gas hot water systems rated at 5 stars or above are the next best option to solar. Tank systems may be a more efficient option for households with four or more people. LPG is roughly on par with natural gas in terms of environmental impact, although it costs more.

3. Heat pump

Heat pump technology ranks above electric storage in terms of efficiency, but it still uses electricity and makes a higher contribution to greenhouse gas emissions than a gas powered system. If gas or solar are not available or viable where you live, this is the more efficient alternative. Geothermal systems also use similar technology.

4. Electric

Electric tank systems are inefficient. Each one in Australia puts out, on average, over four tonnes of greenhouse gas per year. These systems are currently the target of a federal phase-out. If you are replacing one of these systems, consider other options to see if you could save money and the environment. Continuous flow electric systems are slightly more efficient, but are uncommon because they are expensive to run, and usually require three phase power.