It is not about how you use your energy personally but rather the performance of the building. It may sound unfair but it makes no difference to the assessment in how good you may be at turning off unused appliances, turning down thermostats or reducing use of washing machines and other power hungry items.
In order to be fair the EPC score must reflect a known set of values such as the “U value” of older double glazing (pre 2002) compared to more recent technology. Also whether a home has older solid brick walls compared to a house that has cavity walls that may also contain some form of insulation.
When making improvements insulation is often the key. It is no good upgrading to a more efficient heating system if cavity walls are not filled or loft insulation not upgraded. An important section of the EPC is Recommendations and the order in which they should be followed.
