Sometimes we might need to estimate your energy usage rather than bill you on actual data because:

• the meter reader couldn't access your meter. This could be due to a locked gate, an overgrown shrub or a pet guarding your property.
• you're on monthly billing with a basic meter.
• your meter is broken or faulty.

Find out more about Estimated bills.

A bill cycle is between one and three months.

The bill cycle date is the date in the month or quarter that your bill is generated and sent to you. For example, your bill might be generated on the 15th of the month. Quarterly or bi-monthly bills come every two-three months.

Manage your bill frequency

You can choose to be billed monthly to break billing down into smaller payments and make budgeting easer. For non-smart meter customers on monthly billing, up to two out of every three bills can be based on an estimate of your usage, taking into consideration your usage history and seasonal data.

In My Account:

1. From the My Account dashboard, select your name in the top right corner, then ‘Account Settings’
2. Select 'Billing and Payments' and then 'Bill Frequency'.

In the AGL app:

1. In the AGL app go to 'Account'
2. Select 'Setting' and then 'Monthly Billing'.

Pro-rata billing happens when our energy rates change during your billing cycle. For example, if the new rate begins on day 20 of a 30 day billing cycle, there are 10 pro-rated days on the new rates and 20 pro-rated days on the old rates.

To work out your bill, we calculate your average daily energy usage for the billing period. From this, we can work out your usage on both the old rates and new rates, which are added together to make up your bill.

Your bill projection in My Account and the AGL app helps you understand the future costs of your next bill.

It's an estimated total of what your bill will be at the end of your billing cycle, whether its monthly, bi-monthly or quarterly.

If you have a basic meter, you can improve the accuracy of your bill projection by submitting a meter read.

You can also keep an eye on your cost to date in My Account or the AGL app. This will tell you the estimated cost from your last bill up until today.

Find out more about how your project bills are calculated by visiting Usage calculations.

It's possible that two similarly sized houses right next to each other, that are billed for the same time period and pay the same energy rates under identical energy plans, might have very different amounts on their energy bills.

This can be due to the way the occupants use energy, a number of physical factors about the property or the number of occupants, such as:

• Household occupants may use their appliances at different times of the day, when different Peak, Off-peak or Shoulder time rates apply.
• Occupants might do more loads of washing, while others may line dry their clothes or use a tumble dryer.
• Energy hungry appliances, such as refrigerators, washing machines and dishwashers. A second fridge can also add considerable cost to a household electricity bill.
• Appliances left on standby and not being actively used.
• Inefficient heating or cooling can be expensive, or occupants use settings at different temperatures.
• Homes with double-glazed windows, insulation and weather proofing are more energy efficient.
• Homes with solar systems cut energy costs by generating their own electricity.
• Energy efficient lighting uses less energy compared to a home with a large number of inefficient down lights.
• Heated and filtered backyard pools can add significant cost to a household electricity bill.

All of these factors combine uniquely for every household, resulting in quite different amounts when the energy bill arrives. To understand more about how you use energy, monitor your energy usage in My Account or the AGL app.

You can also get handy break downs of your usage by signing up for Energy insights.

The heating value is used to calculate the amount of energy (megajoules) contained in gas, which is impacted by temperatures and pressures at different geographical locations.

We need to calculate your bills by using the heating value provided by your Gas Distributor (they’re responsible for reading your meter, along with the gas pipes and meters in your street).

Your gas meter measures gas usage in cubic meters, but in most states your usage is actually billed in ‘megajoules’ (MJ) on your bill. In WA only, usage is measured in 'units'. A unit of gas is equivalent to 1 kilowatt hour of energy. To determine units, the number of megajoules is divided by 3.6.

To calculate the number of megajoules you've used in a billing period, first we subtract the start read on your meter from the end read, and then multiply the result by two values - the heating value and pressure factor.

Both of these values are provided to us by your local gas distributor - the company responsible for reading your meter and maintaining the pipes in your area. Heating value and pressure factor vary based on local conditions at different geographical locations, such as temperature, pressure and the appliance consuming the gas.

All of the values used in these calculations are shown in the 'meter details' section of your gas bill. Here's an example of how they look:

Here's an example of the calculations using these numbers:

• ( End read - Start read ) x Heating value x Pressure factor = Usage MJ
• ( 4,187 - 4,045 ) x 38.7186 x 1.0123 = 5,565.66