Water heating

More information on water heater types

• Electric storage water heaters

  An electric storage water heater is usually cheap to buy but expensive to run.

  They consist of an insulated storage tank, usually cylindrical, where hot water is kept ready to be used. The water is heated in the storage tank by one or more electric heating elements.

  Over time, the water temperature decreases through heat losses from the storage tank and from hot water that has been used. This results in the tank being refilled with cold water which in turn lowers the overall temperature of water in the tank.

  This water is then re-heated. How this works depends on your electricity tariff.

  • If you are using a continuous electric tariff for your electric storage water heater, the heating elements will be turned back on when the water temperature drops below a certain point.
  • If you are using a restricted tariff, such as an off-peak or ripple control tariff, the heating elements will only operate at certain times. Larger tanks are often used with restricted tariffs, to make sure you don’t run out hot water.

• Gas storage water heaters

  Gas storage hot water systems use a gas burner located underneath the storage tank to heat the water. They usually have a continuously burning pilot flame that ignites the main burner when it is needed.

  When hot water is drawn off at the top of the tank, cold water enters the tank at the bottom.

  Most units have an adjustable thermostat to set the water temperature. When the temperature of the water falls below the thermostat level, the pilot flame ignites the main burner to re-heat the water.

• Instantaneous gas water heaters

  Instantaneous gas hot water systems, also known as continuous flow, don’t have storage tanks and heat water only when required.

  Water is heated by a gas burner as it flows through a coiled pipe called a heat exchanger. The gas burner starts when a hot water tap is turned on. It only heats the amount of water that is required instead of continuously heating a full tank. As they don’t continuously store hot water, there is less heat loss. This means there may be energy and cost savings.

  However, instantaneous units supply hot water at a lower pressure than storage systems, which can be a problem if you use a lot of hot water.

• Solar water heaters

  A solar water heater uses energy from the sun to heat water for your home, using Australia’s abundant sunshine to save energy, money and greenhouse gas emissions. They may be more expensive up front, but can save money in the long run.

  Solar panels or collectors on your roof use energy from the sun to heat water that flows to a storage tank, which is either installed on the roof or at ground level.

  In areas with less mid-year sun and long cold nights, solar hot water units may require a booster using gas or electricity.

• Heat pump water heaters

  Heat pump water heaters absorb warmth from the air and transfer it to heat water. They work on the same principle as a refrigerator, but instead of pumping heat out of the fridge to keep it cool, they pump heat into the water. 

  They operate on electricity but are roughly three times more efficient than a conventional electric water heater. While they may cost more up front, their lower running costs can save you money in the long term. 

  If you are in a cold climate and looking at buying a heat pump water heater, choose a heat pump that has been specifically designed for the cold and will still work if there is frost or snow.

• Instantaneous electric water heaters

  Instantaneous electric water heaters use electricity to heat water on demand, and don't store hot water in a tank.

  They are less common than electric storage water heaters.

  Instantaneous electric water heaters typically require high power inputs, particularly if more than one unit is running at once. In some cases three phase power is required, in others single phase power is adequate.