The 'main heating fuel' reported at the bottom of the EPC is determined by SBEM as either the heating fuel or the hot water fuel depending on which of these 2 systems consumes more energy. In some buildings, fuel consumption due to hot water generation is greater than that required for space heating and in these cases the fuel reported here will be the fuel for HW generation not space heating. Take a look at the 'Energy and CO2' report to confirm that this is the case.