The Carrier Infinity ultra-efficient Gas Furnace - has an efficiency rating of 96%. In other words - 96% of the energy in the fuel is converted to heat, only 4% escapes out the vent to atmosphere. We were definitely due for a new furnace; our 1750 sq. ft. two-story townhouse, built in 1961, still had its original furnace - solid and reliable, but with about a 60% efficiency rating. So for every cubic meter of natural gas that was burned to heat our home 40% went up the chimney, and I had to pay for heating the great outdoors... The main features of this unit are: - - No Chimney - o There are two 2" plastic pipes - one brings fresh combustion air into the furnace - and the other is an exhaust vent - it can be vented through the wall - so no holes through the roof - - Its compact size - o The furnace measures 41" H x 19" W x 29" Deep. Not including ducting or air filter unit. - - 3-speed DC fan motor - o The DC motor uses much less energy than an AC motor - and speeds up or slows down depending upon the heat requirements - on slow setting - the fan stays on all the time - circulating air through the home and eliminating cold drafts - and then speeds up when heat is required. We have noticed the ambient air temperature to be steady - no hot / cold surges as with the older furnace - - Computerized thermostat control - o We had the Infinity Comfort Control thermostat installed. This programmable control is like having a butler in the house - if we select cooler temperature for sleeping - then set for 0700 to raise the temperature - the control unit starts heating the house before the required time - based upon temperature demands over the past history - so that the home is warm at 0700 when the alarm goes off - these little luxuries have made a lot of difference in the level of comfort we are enjoying!! Our infinity ultra Efficient Furnace was installed in the early part of November - just in time for cooler weather - and now we are testing it with COLD weather (-40 - the same in both Fahrenheit or Celsius) The unit has performed flawlessly for us so far - and with the professional installation - we expect many years of energy efficient warmth.