All the suppliers want is for you to use one
Ask your energy supplier what is a typical uncertainty of measurement for one of their smart meters, refer to ISO/IEC Guide 98 . Every measurement has uncertainty. It also relates to the individual meter, smart or non smart. After all if you use a rule guaranteed accurate at 20 degrees C. It does not mean that your measurement made at 20 degrees C is correct, there are other factors to take into account. If you wish to explore this topic further go here:
It is not the same as accuracy and will send the recipients of any enquiry into orbit since most of them will have never heard of it and it requires quite a high level of maths to understand the calculations fully. Since most these meters use some form of wireless communication with the Energy Co the uncertainties may be very large. If they use mobile band methods, GCHQ has indicated that the mobile band relying on legacy protocols are vulnerable to evil doers. All I’ve be able to ascertain is that if these meters go above 50% of their planned accuracy they are rejected so I’ve been told the remaining 50% of the accuracy band is to take into account the individual uncertainties. Go for one if you wish, after all you are paying for them via your standing charge.
But this gent will be steering clear of these meters!