High efficiency is a term used when describing a furnace or boiler that can transfer most of the heat from the fuel that’s being burned to either the air or water. High efficiency equipment refers to equipment that is 90% AFUE or above. AFUE is an acronym for Annual Fuel Utilization Efficiency, which is a measure of how efficiently your furnace can utilize its fuel. The more efficient your furnace, the more heat you will get per unit of fuel.
How do I know if I have high efficiency equipment? There are a few ways you can tell. You can look up the model number. Or, there is AFUE rating sticker comes attached to the equipment. Although, this sticker ends up gets taken off 99% of the time. The best way you can tell is that the equipment gets vented out of the house in PVC pipe. The only exception are power vented hot water heaters. They are truly not high efficiency equipment. In a high efficiency furnace, there are two heat exchangers. The secondary heat exchanger is what makes the furnace more efficient. When the combustion gases travel through the secondary heat exchanger, they get lowered past it’s dew point temperature and start to condense. When they condense, it gives up more heat to the walls of the heat exchanger which in turn gets transferred to the air going over the exchanger.
Should I see a reduction in my utility bills when I replace with high efficiency equipment? It depends. High efficiency equipment is more efficient. BUT, to get the most out of the equipment, it needs to be installed properly. Proper sizing and duct work is crucial. You need to have the correct amount of airflow to carry the heat off of the heat exchanger. If you can’t achieve that, then the heat gets wasted and gets carried out the exhaust vent.