§10.4. Policy. — Inbound Citations

(4) The energy factor for furnaces, expressed in percent, is the ratio of annual fuel output of useful energy delivered to the heated space to the total annual energy input to the furnace determined according to either section 10.6 of appendix N of this subpart (for furnaces, excluding low pressure steam or hot water boilers and electric boilers) or section 10.4 of appendix EE of this subpart (for low pressure steam or hot water boilers and electric boilers), as applicable.