Knowing how you are charged for the electricity and gas you use, and how your use is measured, can help you to keep track and take control of your energy bills.
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How electricity use is measuredHow gas use is measuredHow you are charged for your electricity and gas usePeak and off-peak electricity tariffs How electricity use is measured
The amount of electricity an appliance uses is measured in watts (W). One thousand watts is equal to one kilowatt (kW) - ie 1000 W = 1 kW.
The amount of electricity an appliance uses over a certain time period is measured in watt-hours (Wh). To calculate the amount of electricity an appliance uses over time:
- appliance input watts x hours of use = watt hours (Wh)
To convert watt hours (Wh) to kilowatt-hours (kWh) divide the number of watt hours by 1000.
For example:
- a 500 W appliance running for 1 hour will consume 500 Wh or 0.5 kWh
- a 1000 W appliance running for 3 hours will consume 3000 Wh or 3 kWh.
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How gas use is measured
A gas appliance’s use of energy is measure in megajoules per hour (MJ/hr).
The amount of energy this appliance uses over a certain time is measured in megajoules (MJ). One megajoule is equivalent to 1,000,000 joules.
To calculate the amount of electricity an appliance uses over time:
- appliance input megajoules per hour (MJ/hr). x hours of use = megajoules
For example:
- a 40 MJ/hr appliance running for 1 hour will consume 40 MJ.
- a 40 MJ/hr appliance running for 3 hours will consume 120 MJ.
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How you are charged for your electricity and gas use
Energy providers charge for each electricity kilowatt-hour or gas megajoule you use.
The price you are charged per kilowatt-hour or megajoule is called a tariff. Electricity is charged in cents per kilowatt-hour (c/kWh) and gas is charged in cents per megajoule (c/MJ).
Your energy bill will show:
- the current and previous meter readings or an estimated reading for the billing period if your provider was unable to access your meter
- the dates for the period you are being charged for
- your total energy use or estimated use
- the tariff rates, supply charges and other applicable fees
- solar feed-in tariff for homes that have solar panels and put energy back into the grid.
The tariff rates depend on your energy contract and can differ between energy providers. Compare your current electricity and gas prices and plans with those offered by other energy providers to see if you are getting the best deal.
If there is a problem with your energy bill the first thing you should do is read your electricity or gas meter to ensure you are being charged correctly for the amount of energy you have used.
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Peak and off-peak electricity tariffs
Most of the items in your home that use energy will be recorded to your peak electricity meter and charged at the peak tariff.
To be charged off-peak tariffs you need to have an off-peak meter.
The off-peak electricity tariff is primarily used for permanently installed electric storage water heaters with capacity of 125 litres or more.
Other appliances that can be hard-wired by a licensed electrician to the off-peak meter include:
- underfloor heaters
- swimming pool and spa heaters.
Contact your energy provider to find out when your off-peak hours are and what appliances can be connected to the off-peak meter, see the list of energy providers from the Essential Services Commission of South Australia.
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More information
On this site
Running costs of appliances
Dealing with a high energy bill
Problems with your energy provider or bill