Gas Bill Calculator
A gas bill from your usage — in megajoules, kilowatt-hours, therms or cubic meters — at your rate, plus the daily supply charge, with the usage converted into every unit and the effective price per kilowatt-hour that lets you compare gas with electricity.
Gas is sold by energy, but the unit differs by country: megajoules in Australia, kilowatt-hours in Britain, therms in the United States, and cubic meters on the meter itself, which the retailer converts using the gas's heating value.
How the gas bill calculator works
Gas is sold by energy, but the unit differs by country: megajoules in Australia, kilowatt-hours in Britain, therms in the United States, and cubic meters on the meter itself, which the retailer converts using the gas's heating value. The energy charge is usage times the rate for that unit; the supply charge is a fixed amount per day. Converting everything to kilowatt-hours is what makes gas and electricity prices comparable.
Formula: energy charge = usage × rate; supply = daily charge × days; 1 kWh = 3.6 MJ; 1 therm = 29.307 kWh; m³ × heating value (MJ/m³) = MJ
Worked examples
| Inputs | Bill for the period | Note |
|---|---|---|
| A typical winter bill | 141 | energy plus supply |
| Low usage | 43 | a small bill |
| From the meter in m³ | 295 | converted by heating value |
FAQFrequently asked questions
Why is gas billed in different units?
Habit: Australian bills use megajoules, British ones kilowatt-hours, American ones therms. The meter measures volume, which the retailer converts to energy with the gas's heating value.
How do I compare gas with electricity?
Convert both to kilowatt-hours and include the daily charges. Gas is usually a third to a quarter of the price per kilowatt-hour, before appliance efficiency.
What is the heating value?
The energy in a cubic meter of gas — 38 to 40 MJ for natural gas, higher for LPG. It is printed on the bill and varies slightly by network.
Why is the supply charge so large on a small bill?
Because it is fixed: a home that barely uses gas pays the same daily amount as one that heats with it. Below a few hundred kilowatt-hours a year, disconnecting can be cheaper.
Does the effective price change with usage?
Yes — the daily charge is spread over more energy as usage rises, so the all-in price per kilowatt-hour falls. That is the number to use when deciding whether to keep gas.
Where these figures come from
- International Energy Agency — Energy Efficiency — appliance consumption and standby power context
- US Energy Information Administration — the federal energy statistics agency
Last checked: September 2026. Appliance power figures are typical ratings; check the label on your own equipment, which is authoritative for it.