The paper discusses a program to demonstrate the capability and potential of photovoltaic (PV) systems as a pollution mitigating energy replacement for fossil fuels. The approach has been to install and monitor PV systems located on rooftops of residential, commercial, and military buildings across the U.S. The economic value of the PV systems is enhanced by this approach because they compete with the retail price of electric power rather than the utility avoided cost price. Participating utilities provide hourly records indicating which load-following power plants (marginal or 'swing' plants) are operating as well as total utility system load. The project tracks on a site-by-site basis carbon dioxide (CO2), nitrogen oxides (NOx), sulfur dioxide (SO2), and particulate avoided emissions.