This debate rages around the country – and people have a hard time working through the calculations. Thank you for taking a comprehensive approach to figuring out usage and payback time. This is really helpful. It’s great that municipalities are offering incentives to replace old furnaces with more energy efficient ones. At http://www.energysavvy.com/rebates/ we are continuously updating our site with the latest applicable rebates from all sources. With national focus on energy efficiency on the rise, more and more rebates are becoming available from additional sources to help homeowners save money and get comfortable!