Cooling mode looks fantastic. Even though you spent a little less (electric) in 2010 than in 2008 & 2009 (May-Sept), your Cooling Degree Days (CDD) were much greater in 2010 than either of the prior two years (see below.) Looking at kWh (a better way to look at this since it removes the effect of electric rates), you had (May-Sept) 8% higher kWh usage (comparing 2010 to 2009), but 45% higher cooling degree days (see below) for the year. You can tweak these figures to include April and October kWh if you want and re-figure the percentages. Here are some figures from weatherdatadepot.com and weather station (K)NXX (Willow Grove Naval Air Station) Cooling Degree Days 2010 2164 2009 1490 2008 1726 I haven't looked at the Heating Degree Days (HDD) in a lot of detail. Depending on natural gas (I assume you had natural gas) prices vs electric prices, the difference may not be as great as straight electric in cooling mode. However - what happened with your 1870 kWh dated 1/9/2010? Comparing kWh to HDD doesn't seem consistent for this period. HDD (from a different web site) were: 11/2010 426 12/2010 905 01/2011 1023 02/2011 709 How confident are you that the aux heat is totally disabled? Was the set point higher?