What you need to be aware of is:
1) the meter measures gas consumption in cubic feet (by volume of gas)
2) different gas sources produce different amounts of heat for the same volume. Therefore the supplier converts from cubic feet (the meter reading) to kWh (the energy provided). It does this on the bill. Somewhere on a bill you will find a figure quoted for the conversion factor - it varies by region. Typically 100 cu ft (one Unit on the meter) equals 30kWh.
3) You then pay a price per kWh - typically around 5p per kWh.
Electrical equipment may well be measured in Watts.
But 1 Joule equals 1 Watt for 1 second, and Joules is a measure of heat, oh, enlightened one.
Therefore Watts x time measures heat.
And the answer to that is a banana.