Hot water

What is the most energy efficient type of hot water service?

If you need of a new hot water system or if you are looking to replace one then it’s important to be as energy efficient as possible. Hot water systems can often be responsible for 16% of household energy usage and they can last for around 10 years, so choose carefully.

There are a few things to consider before choosing a system, like:

  • What time of the day do you use hot water the most?
  • How much hot water do you need?
  • How much roof space do you have?
  • How much outdoor area do you have?
  • What type of electricity supply do you have? Green Power? ‘Normal’ brown-coal power? Or maybe your own solar PV roof top array?”

There are varying types of both gas and electric hot water systems. Some systems even use wood. Some systems heat the water and store it in a tank; whilst other heat the water instantaneously, without the need for storage. Electric-based hot water systems can also be powered from solar electricity. Or alternatively there are solar hot water systems that heat water directly from the sun (often called “solar thermal”). All solar hot water systems require a back-up heating system for low sunshine days (e.g. winter), which can be provided by either gas or electric technology.

Gas instantaneous hot water systems can be relatively efficient (as compared with other gas systems), however they are nowhere near as efficient as heat pump hot water technology. Heat pumps use the same technology is a reverse cycle air conditioner, creating additional units of heat output for every unit of electricity input. Gas hot water systems also can’t be powered from solar electricity and ultimately are reliant on a fossil fuel.

Whilst solar hot water can be a good option, it is worth considering the roof space taken up with a solar hot water system, which only heats water, as opposed to using the same roof space for solar panels, which can provide power to other appliances (including an electric hot water system). In order to utilise renewable energy (either from your own solar array or by purchasing GreenPower or similar from your retailer) we recommend installing an efficient electric hot water system. Heat pumps are the most efficient electric systems to heat water and are ideal for households with higher hot water needs and space for a water storage unit. If you have a small to medium hot water usage, traditional electric storage water heaters can be a good option where powered by solar PV. This is a particularly good option where a householder has an existing electric storage water heater or existing solar PV – or both! Changing the timer on the hot water system to the day time and ensuring it runs on the main circuit to which the solar PV is connected will ensure that for most of the year, the hot water load will be powered from the sun. You may need to get a professional to reprogram the timer on your system.

Use less hot water

No matter the system you have, reducing your hot water usage can have a big impact on your overall energy usage. Here are some of our favourite tips!

  • Install water efficient showerheads to reduce hot & cold water usage. Showers typically use the vast majority of your hot water, and water heating often constitutes around 40% of your energy bills. This makes installing an efficient showerhead a good investment for both reducing your water and energy bills.

  • Use cold water when washing your hands, shaving or cleaning your teeth
  • Take shorter showers, ideally 4 minutes or less. Use a shower timer as a reminder.
  • Fix leaking taps and appliances.
  • Wash laundry in cold water. This can save you around $100 per year.
  • Make sure the thermostat of your hot water system isn’t too high. For a storage hot water system set it to 60°C and for an instantaneous hot water system set it to 50°C. Too high a temperature means that energy is used unnecessarily.
  • Maintain your hot water system and have it serviced according to manufacturer’s instructions. This will extend the life of your hot water system.
  • Install tap aerators or flow controllers to reduce water flow