Energy is essential to our society to ensure our quality of life and to underpin all other elements of our economy. Renewable energy technologies offer the promise of clean, abundant energy gathered from self-renewing resources such as the sun, wind, earth, and plants. Virtually all regions of the United States and the world have renewable resources of one type or another. Renewable resources currently account for about 10% of the energy consumed in the United States, most of this is from hydropower and traditional biomass sources. Wind, solar biomass, and geothermal technologies are cost-effective today in an increasing number of markets, and are making important steps to broader commercialization. Each of the renewable energy technologies is in a different stage of research, development, and commercialization, and all have differences in current and future expected costs, current industrial base, resource availability, and potential impact on greenhouse gas emissions. The technical status, cost, and applications of major renewable energy technologies and implications for increased adoption of renewables will be reviewed.