Everything you need to know about gas hot water heaters


Gas systems make up approximately 48 per cent of hot water heaters in Australia.

Gas water heaters include the following types :

  • gas storage water heaters
  • instantaneous or continuous flow gas water heaters
  • solar water heaters with instantaneous gas boosting

They heat the water using either reticulated/piped natural gas or Liquefied Petroleum Gas (LPG).

sydney gas hot water storage tank example

How gas storage hot water heaters work

How gas storage hot water systems work

Storage gas hot water systems heat the water using a gas burner located underneath the storage tank.  They usually have a continuously burning pilot flame that ignites the main burner when it is needed. Heat is then transferred from the gas burner through the bottom of the cylinder. Some heat also flows from the hot flue pipe into the water. When hot water is drawn off at the top of the tank, cold water enters the tank at the bottom.

Most gas hot water heaters have an adjustable thermostat which can be set to the water temperature. When the temperature at the bottom of the tank drops below the level set on the thermostat the pilot flame ignites the main burner so the water is kept constantly hot. The energy from the pilot flame is not wasted as it helps to heat the water in the tank.

Storage gas hot water systems come in a range of tank sizes from 90 litres to 300 litres.

sydney gas hot water instantaneous system example

How instantaneous gas hot water heaters work

How instantaneous (continuous flow) hot water systems work

Instantaneous gas hot water systems, also called continuous flow, don’t have storage tanks and heat water as required.  A gas burner heats the water as it flows through a coiled pipe called a heat exchanger.  The gas burner starts when a hot water tap is turned on, only heating the amount of water that is required instead of continuously heating a full tank.  This is more economical as there is no heat loss caused by storing hot water in a tank.

To allow enough time for heating, the water is slowed down as it flows through the heat exchanger. This means that instantaneous units supply hot water at a lower pressure than storage systems. They can typically deliver hot water at flow rates per minute of between 10 litres and 30 litres, depending on the model.

Questions to ask yourself before buying a new gas water heater

Whether your old electric water heater has failed, or you want to upgrade to a new tank that better caters to your household hot water usage requirements, below are our top tips aimed at helping you make the right choice.

Consider the following when choosing the best system for your requirements
  1. How much hot water do you use?
  2. What times of day do you use the most hot water?
  3. What is your house size?
  4. How many people live in your household?
  5. Are there alternative energy sources available in your area like gas and solar that may be more economical?
  6. Are there any off peak tariffs available in your area?

Once you have the answers to these questions, contact our experienced technicians and we can advise you which electric hot water heaters will best suit your requirements. Call us today on 1800 266 999.

Need advice choosing the right gas water heater for your home? 

Call one of our experienced technicians today who are happy to advise you on what gas hot water heaters would best suit your household usage requirements. We can also advise whether it may be more economical to switch to gas hot water or a solar system. All our advice is free and without obligation. Call us today on 1800 266 999.

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sydney water heaters