The “Dual” heat designation comes out of the utility analysis. If there is any significant correlation between electricity use and Heating Degree Days (HDD)s, then it will be picked up as dual heat. Sometimes this can be triggered by the blower fan energy. If OptiMiser has selected Dual Heat and you are unaware of any established source of electric heat, then you may want to ask the home owner they use portable space heaters. If you are certain that there is no electrical source of heat, then you should uncheck the “Auto” box and change the selection to Fuel Heat.