Furnace Efficiency Measurement
The measurement for efficiency is called an Annual Fuel Utilization Efficiency (AFUE) rating. All furnaces produced are required to provide this rating, generally in the form of the yellow “Energy Guide” label. AFUE ratings can range from the 78% minimum to 98.2%. The US Department of Energy considers units with an AFUE of 90% or higher as “high-efficiency” and models with an 80% – 83% AFUE as “mid-efficiency.” The yellow Energy Guide lists the estimated annual operating costs for furnaces under specific conditions and are meant for comparison only. Your installation circumstances will affect your final results.
How much will you spend to replace an old furnace with a new, high-efficiency model? That depends upon quite a few circumstances. If the new unit can be connected to existing ductwork and exhaust flue, it should run from about $3,000 to $4,500, installed. Often, the higher the efficiency of the furnace, the higher the initial price. Consider that a high-efficiency unit may cost $500 to $1000 more than a mid-efficiency unit, but you are paid back with energy savings and may qualify for rebates or tax credits. The pay back period will depend on local energy prices, your climate, cost of the new system and the difference in AFUE between the old and new units.