Gas and oil furnaces are rated by Annual Fuel Utilization Efficiency (AFUE); this number, a percentage, indicates how much of your fuel is used to heat your home and how much is wasted.
The higher the AFUE rating, the greater the efficiency.
For example, if a furnace has a rating of 80%, the furnace converts 80% of the fuel that you supply to heat and 20% is lost out the chimney. Older furnaces waste as much as 50% of every energy dollar, although most furnaces still in operation today are 60-80% efficient.
The trend has been to replace these inefficient furnaces with condensing gas furnaces. The most efficient furnaces in the industry, Lennox condensing gas furnaces, reach AFUE efficiency ratings over 98% and can save up to 25% of your electricity bill too!
Fortunately, newer variable speed ECM blowers in many new furnaces can move air more efficiently at a fraction of the cost. Savings are most often $300.00 to as much as $500.00 per year! This is becoming even more significant with rising power costs and the HST tax on energy bills.