Its just the odd way they got in touch, almost panicing me. Saying it wasnt certified. I wondered if a hard sell tactic to get a smart meter despite my requesting not to have one. Ive emailed Eon for advice and clatiry.
It is a legal requirement that all electricity metering equipment has to perform to a fairly precise tolerance. Over time most meters tend to drift a little bit and meters are certified for a fixed period of time during which they are generally accurate to the required tolerance. Outside this certification window, they are no longer deemed to be accurate.
Now, if your meter is an electronic unit like a Landis and Gyr digital display meter, these are likely to remain reasonably accurate even outside the certification window. I have one of these that the certification date ran out about ten years ago. I have two additional sub-meters in my property which are only a year or so old and I can tell than my main meter is still well within tolerance.
However, if your meter is one of the old analogue meters, like a Smiths, with the spinning disc and the rotating numbers, it's almost certain that outside of the certification period, the meter will tend to over-read. The longer the meter is in use after this date, the tendency to over-read will increase with time. This is due to mechanical wear in the bearings that support the disc-spindle. As the bearings wear, the friction decreases which causes the disc to rotate slightly faster for a given consumption thereby causing the meter to rack up more units than have actually been used.
So if you have one of these types, it is very much in your interest to have it replaced.
It's pretty much a given your new meter will be smart, but even if you don't have connectivity and the meter doesn't 'phone home', at least it will record your consumption correctly. So even without the alleged benefits of smart metering, you will at least have a meter which is more accurate!