Again depending on the efficiency of the equipment used. First for fossil fuel furnaces like natural gas, LP and oil; The annual fuel utilization efficiency (AFUE) is a thermal efficiency measure of combustion equipment like furnaces, boilers, and water heaters. If the heating system is 90% efficient then $0.90 of your $1.00 heating cost goes to heating your house but $0.10 is lost in the exhaust.
Second, HSPF (Heating Seasonal Performance Factor) HSPF is specifically used to measure the efficiency of air source heat pumps. A heat pump with a high HSPF is more efficient than a heat pump with a low HSPF.
New heat pumps manufactured after 2005 are required to have an HSPF of at least 7.7. The most efficient heat pumps have a HSPF of 10.



