Accuracy Class for Energy Meters

If the meter can't tell the difference, probably nothing. Otherwise, something like the difference in precision/accuracy of the two CTs. And even then, if your class 0.2 CT happens to be "lucky", maybe still no difference.

The difference will be either some, or none.

Read this and learn:

Accuracy Limit Factor and Instrument Security Factor of ...

Disregarding the uncertainty introduced by the meter and the PTs, the difference due solely to the CTs will be on average 0.8%. So if this is a residential meter and it reads 1,000 kWh for the year you will be under/over paying for 8 kWh.

In reality the number is probably smaller because as you have more ITs (Instrumentation Transformers) involved the overall statistical error is lower due to the positive errors in some ITs being cancelled by the negative errors in the others.

There are many technical aspects that need to consider before. An digital meter will have certain precision class and range where the meters performance will be as per commited accuracy, also factors like uncertainty which depends on samples per cycle etc.

To simplify answer to your query, system accuracy will depend on sq.root of sum of (instrument transformer accuracy square & meter accuracy square)

This is one way of deriving the final system accuracy of individual instruments/meters.

if u use 1.0 class CT then there will be 1% error in measurement and for which exclusively the CT will be responsible..............there will be another 0.2 % measurement error for which the meter will be responsible