Being located in Arizona, having a reliable furnace is a necessity for the extreme winter temperature fluctuations. When my home was built, it was located within a development common to my area. I was expecting nothing short of an unreliable heating and cooling system, but I was pleasantly surprised. When I moved in, it included a well taken care of Rheem Criterion gas furnace system. From my best estimate, the unit is a little over 10 years old. Although this unit rarely sees temperatures below the 30s, it runs like a champion! I have noticed that in conjunction with my thermostat, the unit runs properly and my energy bills in the winter months in Arizona reflect this. We have made some plans to improve any drafts or air leaks, so in conjunction with the furnace, our energy bills are more manageable than in the summer months. I would have to say one of the only downfalls to this unit is the accessibility of the filter. This may be because of the location it was placed in, but it is pretty difficult to access it to change it. Overall, I am happy that I have a Rheem, and I would certainly recommend it to a friend!