Get App
Megajoules (MJ): Gas usage and costs explained
24 July 2025
KEY POINTS
- MJ represents megajoule, a unit of energy equaling one million joules or one thousand kilojoules that is used to measure gas usage for heating and other appliances.
- Gas usage is charged by cents per megajoule (c/MJ), with actual rates differing between states and networks.
- Gas bills offer key insights, such as daily gas usage trends and gas meter read types.
What is a ‘MJ’ in gas?
MJ is short for megajoule, which is a unit of energy equivalent to one million joules. A property’s gas usage is measured in megajoules and recorded using a gas meter.
This information is then passed on to your natural gas retailer for billing purposes. Your gas usage information (in MJs) will be detailed on your bill, helping you understand your gas usage habits and how you can save.
Gas-powered appliances, such as heaters, usually detail their energy efficiency in terms of megajoule-hours (MJ/h), which represents the number of MJs they consume in one hour. For example, a gas heater with an input of 25MJ/h will consume 25MJs in one hour.
If you see a gas appliance described in terms of just megajoules, you can safely assume it means its consumption is in MJ/h.
If you notice that a gas heater or oven lists a kilowatt (kW) value instead, you can convert it to MJ with a rate of 3.6 MJ to one kWh — this rate is based on the assumption that the appliance is running at maximum efficiency
Compare natural gas plans in your state
Here are some of the cheapest gas deals on our database for NSW. These estimated annual costs are based on the Jemena Gas Network in Sydney and yearly gas usage of 18,800 MJ/year, but prices will vary depending on your own circumstances. The products are listed in order of lowest estimated price/year (including conditional discounts), then by the highest value rank (out of 10), then by highest brand satisfaction rating. These are products from referral partners†. Our database may not cover all deals in your area, and please check retailer websites for up to date information.
Distributed By Jemena Gas
-
12 month energy plan with no exit fees
Glossary
-
No lock in contract with variable rates
Glossary
Distributed By Jemena Gas
-
Ongoing energy plan with no renewal required
Glossary
-
No lock in contract with variable rates
Glossary
Distributed By Jemena Gas
-
Conditional discounts: 2% off the bill when paid on time plus 1% off the bill for direct debit payments
Glossary
-
Ongoing energy plan with no renewal required
Glossary
-
No lock in contract with variable rates
Glossary
Distributed By Jemena Gas
-
12 month energy plan with no exit fees
Glossary
-
No lock in contract with variable rates
Glossary
Distributed By Jemena Gas
-
Conditional discounts: 2% off the bill when paid on time plus 1% off the bill for direct debit payments
Glossary
-
Ongoing energy plan with no renewal required
Glossary
-
No lock in contract with variable rates
Glossary
Distributed By Jemena Gas
-
Conditional discounts: 2% off the bill when paid on time plus 1% off the bill for direct debit payments
Glossary
-
Ongoing energy plan with no renewal required
Glossary
-
No lock in contract with variable rates
Glossary
Distributed By Jemena Gas
-
12 month energy plan with no exit fees
Glossary
-
No lock in contract with variable rates
Glossary
Distributed By Jemena Gas
-
Ongoing energy plan with no renewal required
Glossary
-
No lock in contract with variable rates
Glossary
Here are some of the cheapest gas deals on our database for VIC. These estimated annual costs are based on the AGN – VIC network in Melbourne and yearly gas usage of 40,500 MJ/year, but prices will vary depending on your own circumstances. The products are listed in order of lowest estimated price/year (including conditional discounts), then by the highest value rank (out of 10), then by highest brand satisfaction rating. These are products from referral partners†. Our database may not cover all deals in your area, and please check retailer websites for up to date information.
Distributed By AGN - Vic
-
Ongoing energy plan with no renewal required
Glossary
-
No lock in contract with variable rates
Glossary
Distributed By AGN - Vic
-
Ongoing energy plan with no renewal required
Glossary
-
No lock in contract with variable rates
Glossary
Distributed By AGN - Vic
-
12 month energy plan with no exit fees
Glossary
-
No lock in contract with variable rates
Glossary
Distributed By AGN - Vic
-
Ongoing energy plan with no renewal required
Glossary
-
No lock in contract with variable rates
Glossary
Distributed By AGN - Vic
-
Ongoing energy plan with no renewal required
Glossary
-
No lock in contract with variable rates
Glossary
Distributed By AGN - Vic
-
Ongoing energy plan with no renewal required
Glossary
-
No lock in contract with variable rates
Glossary
Distributed By AGN - Vic
-
Ongoing energy plan with no renewal required
Glossary
-
No lock in contract with variable rates
Glossary
Distributed By AGN - Vic
-
12 month energy plan with no exit fees
Glossary
-
No lock in contract with variable rates
Glossary
Here are some of the cheapest gas deals on our database for QLD. These estimated annual costs are based on the AGN – QLD in Brisbane and yearly gas usage of 8,300 MJ/year, but prices will vary depending on your own circumstances. The products are listed in order of lowest estimated price/year (including conditional discounts), then by the highest value rank (out of 10), then by highest brand satisfaction rating. These are products from referral partners†. Our database may not cover all deals in your area, and please check retailer websites for up to date information.
Distributed By AGN - QLD
-
Ongoing energy plan with no renewal required
Glossary
-
No lock in contract with variable rates
Glossary
Distributed By AGN - QLD
-
Conditional discounts: 2% off the bill when paid on time plus 1% off the bill for direct debit payments
Glossary
-
Ongoing energy plan with no renewal required
Glossary
-
No lock in contract with variable rates
Glossary
Distributed By AGN - QLD
-
Conditional discounts: 2% off the bill when paid on time plus 1% off the bill for direct debit payments
Glossary
-
Ongoing energy plan with no renewal required
Glossary
-
No lock in contract with variable rates
Glossary
Distributed By AGN - QLD
-
12 month energy plan with no exit fees
Glossary
-
No lock in contract with variable rates
Glossary
Distributed By AGN - QLD
-
Conditional discounts: 2% off the bill when paid on time plus 1% off the bill for direct debit payments
Glossary
-
Ongoing energy plan with no renewal required
Glossary
-
No lock in contract with variable rates
Glossary
Distributed By AGN - QLD
-
Ongoing energy plan with no renewal required
Glossary
-
No lock in contract with variable rates
Glossary
Distributed By AGN - QLD
-
Ongoing energy plan with no renewal required
Glossary
-
No lock in contract with variable rates
Glossary
Distributed By AGN - QLD
-
Ongoing energy plan with no renewal required
Glossary
-
No lock in contract with variable rates
Glossary
Here are some of the cheapest gas deals on our database for SA. These estimated annual costs are based on the AGN – SA network in Adelaide and yearly gas usage of 14,800 MJ/year, but prices will vary depending on your own circumstances. The products are listed in order of lowest estimated price/year (including conditional discounts), then by the highest value rank (out of 10), then by highest brand satisfaction rating. These are products from referral partners†. Our database may not cover all deals in your area, and please check retailer websites for up to date information.
Distributed By AGN - SA
-
Conditional discounts: 2% off the bill when paid on time plus 1% off the bill for direct debit payments
Glossary
-
Ongoing energy plan with no renewal required
Glossary
-
No lock in contract with variable rates
Glossary
Distributed By AGN - SA
-
Conditional discounts: 2% off the bill when paid on time plus 1% off the bill for direct debit payments
Glossary
-
Ongoing energy plan with no renewal required
Glossary
-
No lock in contract with variable rates
Glossary
Distributed By AGN - SA
-
Conditional discounts: 2% off the bill when paid on time plus 1% off the bill for direct debit payments
Glossary
-
Ongoing energy plan with no renewal required
Glossary
-
No lock in contract with variable rates
Glossary
Distributed By AGN - SA
-
Ongoing energy plan with no renewal required
Glossary
-
No lock in contract with variable rates
Glossary
Distributed By AGN - SA
-
Ongoing energy plan with no renewal required
Glossary
-
No lock in contract with variable rates
Glossary
Distributed By AGN - SA
-
Ongoing energy plan with no renewal required
Glossary
-
No lock in contract with variable rates
Glossary
Distributed By AGN - SA
-
Ongoing energy plan with no renewal required
Glossary
-
No lock in contract with variable rates
Glossary
Distributed By AGN - SA
-
Ongoing energy plan with no renewal required
Glossary
-
No lock in contract with variable rates
Glossary
Here are some of the cheapest gas deals on our database for WA. These estimated annual costs are based on the ATCO network in Perth and yearly gas usage of 6,300 units/year, but prices will vary depending on your own circumstances. The products are listed in order of lowest estimated price/year (including conditional discounts), then by the highest value rank (out of 10), then by highest brand satisfaction rating. These are products from referral partners†. Our database may not cover all deals in your area, and please check retailer websites for up to date information.
Distributed By ATCO
PROMOTED
-
Conditional discounts: 35% off the usage charge with direct debit & e-billing
Glossary
-
12 month energy plan with no exit fees
Glossary
-
No lock in contract with variable rates
Glossary
Distributed By ATCO
PROMOTED
-
12 month energy plan with no exit fees
Glossary
-
No lock in contract with variable rates
Glossary
Distributed By ATCO
-
12 month energy plan with no exit fees
Glossary
-
No lock in contract with variable rates
Glossary
Distributed By ATCO
-
12 month energy plan with no exit fees
Glossary
-
No lock in contract with variable rates
Glossary
Distributed By ATCO
-
12 month energy plan with no exit fees
Glossary
-
No lock in contract with variable rates
Glossary
Distributed By ATCO
-
Conditional discounts: 35% off the usage charge with direct debit & e-billing
Glossary
-
12 month energy plan with no exit fees
Glossary
-
No lock in contract with variable rates
Glossary
Distributed By ATCO
-
Conditional discounts: 25% off the usage charge with direct debit & e-billing
Glossary
-
Ongoing energy plan with no renewal required
Glossary
-
No lock in contract with variable rates
Glossary
Distributed By ATCO
-
Conditional discounts: 12.50% off the usage charge when paid on time
Glossary
-
Ongoing energy plan with no renewal required
Glossary
-
No lock in contract with variable rates
Glossary
What’s the difference between joule, kilojoule, megajoule and gigajoule?
With many different variations of the word joule, it’s easy to get confused. Here’s a comparison of the terms in order of unit of size:
← Mobile/tablet users, scroll sideways to view full table →
| In Joules (J) | In Kilojoules (kJ) | In Gigajoules (GJ) | |
| 1 Megajoule (MJ) | 1,000,000 | 1,000 | 0.01 |
- Joule (J): Smallest unit, used for scientific purposes or very small energy amounts (e.g. laser pointer heat)
- Kilojoule (kJ): Most common unit for food energy labelling (calories)
- Megajoule (MJ): Ideal for measuring gas consumption of homes, household appliances, industrial processes and large-scale energy generation
- Gigajoule (GJ): Used to express large energy quantities, like energy consumption of cities, natural gas pipeline capacities and large-scale power generation.
What do gas prices charged per MJ look like?
Natural gas customers are charged per megajoule of gas they use. Customers are usually charged on a block rate — which means they’re charged different rates depending on how much gas they use.
Generally, the more gas that is consumed, the lower the usage rate will be for subsequent blocks of usage. For example, a typical gas usage block tariff might look like this:
| First 80MJ per day | 3 c/MJ |
| Next 50MJ per day | 2.8 c/MJ |
| Remaining usage | 2.5 c/MJ |
The figures in this table are a general guide only
The above example illustrates blocks of usage per day. However, some gas providers may describe their blocks in other measures of time, such as months or billing quarters. An example of that might look like this:
| First 5,000MJ per quarter | 3.1 c/MJ |
| Next 2,000MJ per quarter | 2.7 c/MJ |
| Next 1,000MJ per quarter | 2.4 c/MJ |
| Remaining usage | 2.3 c/MJ |
These figures in this table are a general guide only
Keep in mind that gas rates vary across different networks and states. For example, Western Australian and South Australian households tend to spend a little more on gas than customers in other states, while Victorians are often treated to some of the lowest gas prices in the country.
It is also important to note that WA gas bills and price fact sheets display gas usage in terms of ‘units’ rather than MJs, with one unit equivalent to 3.6MJ. This way, gas prices are easily compared against electricity prices. Unlike other states, gas prices in WA don’t vary much between different retailers as prices are regulated by the state government.
To learn more about the cost differences between gas and electricity, visit Canstar Blue’s guide on gas versus electricity.
Average gas usage per day in MJs
According to our database, the estimated gas usage as reported in November 2024 is:
- 18,800MJ on the Jemena Gas Network in Sydney (around 51MJ per day)
- 40,5000MJ on the Australian Gas Network in Melbourne (around 110MJ per day)
- 8,300MJ on the Australian Gas Network in Brisbane (around 22MJ per day)
- 14,800MJ on the Australian Gas Network in Adelaide (around 40MJ per day)
- 33,200MJ on the Evoenergy Network in Canberra (around 90MJ per day).
How to read your gas bill
Note: Keep in mind that the design of your gas bill and the information it includes will vary across retailers.
Now that you have a better idea about megajoules and block rates, you can start to understand your bill a little easier.
The front (page 1)
Conveniently, the amount due and its due date on this existing bill are typically shown on the first page of the bill.
While you might just look at what you owe and then toss the bill out, it’s important to check this section to make sure you’re being charged correctly.
The back (page 2)
The Gas Charges section above the ‘bill period’ indicates whether someone actually read your meter, or if the gas company instead made an estimate to bill you.
In the Previous Balance and Payments section, the remaining balance on your account with your energy retailer will be brought forward from your previous bill cycle.
In the New Charges and Credits section, your plan’s usage and supply charges are broken down, line-by-line. In the example above, your usage rate (e.g. Usage – Step 1) varies with how many blocks of gas are consumed — this is known as a block rate. ‘Service to property’ refers to the cost to supply gas to your property, which is typically fixed.
In the Other Charges and Credits sections, extra fees are then added on as discounts or credits (cr) are subtracted.
The Start Date column indicates the number on your gas meter at the start of this current billing period.
The End Date column indicates the number on your meter at the end of this bill cycle.
The figure in the Quantity column is found by subtracting the start read from the end read.
The next column, Correction Factor, takes into consideration the volume of gas-based pressure and temperature.
Heating Value refers to the amount of heat released through burning a quantity of supplied gas.
Your Total Usage (in MJ) is then calculated by multiplying the base usage by the heating value and pressure factor. The result is your real usage in MJ.
If you’re not being charged correctly, don’t be afraid to take it up with your provider.
Most gas bills will also include a section similar to the one above that provides some insight into your natural gas usage over time.
The bar chart illustrates your average daily gas usage habits and how much it varies from month-to-month during the bill cycle. Your current average daily usage is then compared against your average daily usage from the same time last year.
Knowing this information will help identify trends in your gas usage and whether you need to cut back to save.
Read more: How to read your electricity bill
How to find a better gas deal
Understanding your gas usage is the first step towards finding a better deal. Now that you understand joules, megajoules and everything in between, you’re ready to get out there and compare providers. And what better way than through Canstar Blue’s free natural gas comparison tool? Here, you’ll find plans from about 17 providers and best of all, we won’t ask for any of your personal details. Simply type in your postcode and you’re good to go.
Image credits: tonton/Shutterstock.com
Original reporting by Monika Gudova
This article was reviewed by our Utilities Editor Tara Donnelly before it was updated, as part of our fact-checking process.
