Gas units

Introduction

This article shows ho to convert between the various ways of measure natural gas volume and energy content.

Typically gas meters record usage in cubic metres or hundreds of cubic feet (and its worth checking yours matches the units your gas supplier is billing you in!)

Basic data

The energy density of natural gas is typically in the range of 37.5 to 43 MJ/m³

1 kW equates to 3.6MJ / hour

Converting

Use the following conversion factors to work out what you need from what information you have:

Task	Conversion factor
100 CU feet (1 unit) to cubic metres	Multiply by 2.83
100 CU feet (1 unit) to kWh	Multiply by 32.15
Cubic metres to 100s cubic feet	Divide by 2.83
Convert from m³ to kWh	Multiply by 11.36
Convert from a rate of consumption in kW, to cubic metres per hour	Multiply by 0.09 (approx)
Convert 1000 BTU/h into kWh	Multiply by 0.293

Examples

You have used 40 units on your imperial gas meter. What is that in kWh?

Convert 100s of cubic feet to m³: 40 x 2.83 = 113.2m³

So in kWh = 113.2 x 11.36 = 1,286 kWh

Your new boiler can demand a maximum input power of 24kW. How much is that in cubic meters of gas per hour?

24 x 0.09 = 2.16 m³

(Note that if the boiler specification states the output power rather than the input power, you will likely need to add 10% to 20% to the power stated before conversion to arrive at the actual gas rate. This allows for inefficiency in the boiler, since not all the energy delivered in the gas is converted to usable heat by the boiler)