Gas furnaces can be extremely efficient leading to more cost savings on your utility bills.
In order to calculate a furnace’s energy cost, there are a couple of key factors to consider. The amount of gas it burns and the electricity your furnace uses to run the blowers and controls. Then you take the annual fuel-utilization-efficiency (AFUE) rating, measured by percentage.
A furnace built 30 years ago would have an AFUE rating of 65%, but today furnaces are built at a minimum 78% rating with many high-efficiency models seeing an AFUE of about 97%.