This study provides an evaluation of the performance of five renewable energy technologies used to generate electricity: biomass, geothermal, solar photovoltaics, solar thermal, and wind. The authors compared the actual performance of these technologies against stated projections that helped shape public policy goals over the last three decades. Their findings document a significant difference between the success of renewable technologies in penetrating the U.S. electricity generation market and in meeting cost-related goals, when compared with historic projections. In general, renewable technologies have failed to meet expectations with respect to market penetration. They have succeeded, however, in meeting or exceeding expectations with respect to their cost. To a significant degree, the difference in performance in meeting projections of penetration and cost stem from the declining price of conventional generation, which constitutes a moving baseline against which renewable technologies have had to compete.