The 2024 recast of the Energy Performance of Buildings Directive (EPBD) establishes new provisions for existing buildings as minimum energy performance standards (MEPS) for the worst performing non-residential buildings. One option to implement MEPS is to adjust energy performance certificate (EPC) scale so that class F and G will correspond to 26% and 16% worst performing buildings in the building stock. In such as case class G buildings must be renovated to at least class F from 2030 and class E from 2033. EPBD states that the EU Member States should develop a method that will consider the influence of the behaviour of occupants and the local climate if EPC is based on metered energy [1]. This study examined the user and systems operational hours impact on energy use in one office building. It aimed to develop a method for normalizing the energy use for extended hours. A calibrated simulation model was compiled to compare three cases: the building actual usage with non-standard operational hours, similar case with additional base load, and a standard usage case stated by Estonian regulations. The actual model’s energy use differs about 8–10% and 16–25% from the standard model, respectively for heating and electricity energy use. The normalization method using hourly heating and electricity energy use, and actual and typical operational hours revealed to be reliable to conduct operational hours normalization with a few percent accuracy.