Energy efficiency

Energy efficiency

In future as appliances and housholds improve energy used in a house will decrease by about 50%.


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Efficiency of gas heating

In this example carried out by Zero Carbon Aust. we look at a typical Victorian household using about 60,000MJ of gas, which is 16,600kWh of gas energy. It is used for; space heating, water heating and cooking.

they found that 50% of the heat supplied by gas is wasted.

Space heating

4,200kWh of heat lost:

The average ducted gas heating unit sold in Australia has a 3-star rating, however the average unit installed in the field – due to their 20-25 year operational life – has a 2.5 star rating. This means that 35% of the energy contained in the fuel for the heater (gas) is lost up the exhaust and only 65% flows into the heating ducts.  

1560kWh of heat loss:

A number of studies have shown that newly installed ducting is at best 80% efficient, with 20% losses.

624kWh of heat loss:

There’s the problem of heating ducts installed in rooms with their doors shut. This creates pressure equalisation mismatch meaning air from the duct outlets can’t make its way back to the centralised air intake. Those who are conscientious about their bills and shut off vents to unused rooms make this problem considerably worse.

Final equation:

– Total amount of heat fed into your typical central heater 12,000kWh

– Total amount of heat that is useless and lost to the atmosphere 6384kWh - 53%

– Total amount of energy that is useful for heating the space 5616kWh - 47%

Water heating

1786kWh of heat is lost here:

Gas hot water heaters are pretty inefficient, especially storage heaters and older instantaneous units. Even the newest gas hot water units lose 35% of their heat energy to atmosphere. To illustrate this we took a typical 3-star unit; which experiences 45% energy loss to the atmosphere and 55% useful heat as hot water available in the tank, to be delivered to hot water services such as showers as well as bathroom and kitchen taps



Of all the applications for gas in the home, the most inefficient is gas cooking. However gas cooking does not make up a huge proportion of household energy consumption. Most houses have moved to electric ovens and that leaves just the stovetop still running on gas. Gas stoves use 30% of the heat from gas to heat the food. the rest heats the air in the kitchen. An induction cooktop is three times as efficient with an efficiency of 90%, has better heat distribution, causes much less additional heating load in summer, lowers burns and fire risk and leaves you with better air quality.

Source Matthew Wright Zero Carbon Aust