An Energy Performance Certificate (EPC) is a theoretical measure of how efficient your building could be if it were to be operated in a standardized way. This is very unlikely to match how you will be operating your building in reality.
An EPC is therefore not representative of how your building will perform in operation and an EPC’s sole purpose is to allow comparisons between buildings to be made. i.e. A building with an ‘A-rated’ EPC would be expected to be more efficient than a similar building with a ‘B-rated’ EPC.