Where appropriate, such rules shall include guidelines on the manner in which to allocate cost for energy that is used as follows:
I gcás inarb iomchuí, áireofar i rialacha den sórt sin treoirlínte maidir leis an mbealach is ceart an costas a leithdháileadh i dtaobh fuinneamh a úsáidtear mar a leanas: