ENERGY SOURCES FOR HEATING WATER

Solar energy

Solar hot water systems depending on your climate can provide up to 90% of your hot water for free using the sun's energy. Solar systems may be less appropriate in smaller households, in cooler parts of the country, or where access to sunlight is restricted.

Rebates may be available to assist with the purchase cost of solar water heaters. Rebates are currently available in Queensland, Victoria, NSW and SA.

Natural gas

Natural gas water heaters generate far fewer greenhouse gas emissions than standard electric storage systems.

Gas storage systems have quicker heat recovery times and generally use a smaller tank than a comparable electric storage system. This improves efficiency and makes indoor installation easier. Systems installed inside the house need a flue that leads outside to vent exhaust gas.

Instantaneous systems usually use natural gas as it is cheaper for this application than LPG and electricity.

To compare energy use of gas storage and instantaneous gas water heaters, check the star rating label.

Electricity can be used for standard storage heaters, for heat pump systems or for boosting solar systems. Expensive three-phase electricity supply is needed for instantaneous systems.

Electric Heat Pumps:

Electric heat pumps are an efficient type of electric storage water heater that extracts heat from the environment to heat water. They pay back the extra initial investment more quickly in larger households.

Heat pumps that draw heat from the air use only about one third of the energy of a standard electric system and can be made even more efficient by using a solar booster. Electricity is not used to directly heat the water but to move heat from one place to another. The heat is carried by a refrigerant.

Ground source (or geothermal) heat pumps use a water body, shallow trench or deep bore instead of the air as a heat source. They usually provide both space heating and water heating.Electricity is used to pump water around a loop buried in the ground or immersed in a water body. The enclosed water absorbs heat from the surroundings. Geothermal heat pumps can produce more than 4 units of heat energy for every unit of electrical energy used.

Heat pumps can be located and designed to utilise waste heat from air conditioners and refrigerators.

Government rebates may be available to assist with the purchase cost of heat pumps. Rebates are currently available in Queensland, Victoria and some parts of NSW and SA.

Electric Storage Water Heaters:

Standard electric storage water heaters use a heating element inside the tank to heat the water, just like an electric kettle. They are responsible for the most greenhouse gases of any water heater so are not recommended.

Smaller electric storage water heaters of less than about 160 litres usually use peak electricity and are the most expensive of all to run.

Larger electric storage water heaters generally use cheaper off-peak electricity tariffs where available, heating water at restricted times (usually overnight). To reduce the chance of running out of hot water, tanks are often oversized and overheated, increasing energy consumption and greenhouse gas emissions. An electric storage water heater can indirectly produce as much carbon dioxide each year as the average family car.