When you look at the dial on your gas meter or the meter reading on your gas bill, you're seeing the total volume of gas your household has used in cubic metres (m³). Each movement on the meter dial represents one cubic metre of gas used. 

Your gas bill shows this usage in energy units. This is because gas composition and pressure vary depending on where you are in the gas network, meaning households may use different volumes of gas to receive the same amount of energy. 

To account for these differences, ATCO, WA's gas network operator, converts the volume of gas used into the amount of energy consumed using a heating value and pressure correction factor. ATCO then provides gas retailers, including Kleenheat, with the total number of energy units consumed by a household. 

How your natural gas usage is calculated 

1. ATCO reads your gas meter every three months.
2. ATCO calculates the volume of gas used by subtracting your previous meter reading from your current meter reading.
3. The volume of gas used is converted from cubic metres (m³) to megajoules (MJ) using a heating value and pressure correction factor. The pressure correction factor is based on the average temperature, pressure and elevation of the gas meter at your address.
4. The megajoules are converted into energy units by dividing the total megajoules by 3.6. 

Your gas bill shows both your meter reading and total energy units. 

Formula used to calculate energy units: 

(Current meter reading − previous meter reading) × heating value × pressure correction factor ÷ 3.6 = total energy units 

Current meter reading	Previous meter reading	Volume of gas used (cubic metres)	Heating value*	Pressure correction factor*	Gas usage in megajoules (rounded)	Unit conversion ÷	Energy units^
4121	4093	28	37.91	1.0291	1092	3.6	303

*The pressure correction factor and heating value are unique to your property. In this example, the heating value is 37.91, and the pressure correction factor is 1.0291. 

^referred to as ‘units’ on your Kleenheat bill.  

Please contact us if you’d like information about the pressure correction factor and heating value at your property.