Solar radiation absorption and reflection on roof surfacesaffects heating and cooling energy demand. Prior studies ofenergy costs associated with the long-term trend toward usinghighly reflective roof membranes, (i.e., "cool roofs") are reviewedand shown to have conflicting results in terms of the impact onheating costs. Also, the guidance for membrane reflectivity selectionfor building designers in terms of climate zone and/or heatingand cooling degree days has not been clear. In this paper, both2015 energy costs and insulation codes by state have been usedto model the impact of cool roofs on building energy demand.Assuming natural gas as a heating energy source and electric airconditioning,then the modeled cool roofs are shown to provide anet cost savings across all cities studied, even when long-termmembrane reflectivity values are considered. When electricdemand charges are factored in, there is little correlation betweenthe magnitude of savings and location climate.