A meter serial number is the unique number that applies to a meter be it a gas or electric one. It is also often referred to as 'MSN'. This is different to a supply number.
What is my meter serial number?
Your meter serial number is found on the meter and is often a mix of both letter and numbers. We also put it on your energy statement, so you can find it there. Here's an example of both a gas and electricity meter serial number
How is this different to a supply number?
The supply number (your MPRN or MPAN) is a reference point for the property where the meter is located. It's the point where we put the meter, not the meter itself.
The Meter Serial Number is the number of the meter and so this will change whenever a meter is replaced, whereas a supply number will not.