The conversion factor for heat pump to warm air furnace depends on the specific systems being compared. However, in general, heat pumps can achieve efficiencies of up to 300-400% (COP 3-4), while warm air furnaces typically have AFUE ratings ranging from 80-95%. By dividing the energy output of the warm air furnace by the energy input of the heat pump, you can determine the conversion factor. For example, if the warm air furnace produces 80,000 BTUs of heat using 40,000 BTUs of energy, and the heat pump produces 120,000 BTUs of heat using 30,000 BTUs of energy, the conversion factor would be approximately 1.5 (120,000 BTUs / 80,000 BTUs).