This 54 page report covers voluntary consumer decisions to buy electricity supplied from renewable energy sources; they represent a powerful market support mechanism for renewable energy development. In the early 1990s, a small number of U.S. utilities began offering 'green power' options to their customers. Since then, these products have become more prevalent, both from traditional utilities and from renewable energy marketers operating in states that have introduced competition into their retail electricity markets or offering renewable energy certificates (RECs) online. Today, more than half of all U.S. electricity customers have an option to purchase some type of green power product directly from a retail electricity provider, while all consumers have the option to purchase RECs. This report documents green power marketing activities and trends in the United States including utility green pricing programs offered in regulated electricity markets; green power marketing activity in competitive electricity markets, as well as green power sold to voluntary purchasers in the form of RECs; and renewable energy sold as greenhouse gas offsets in the United States. These sections are followed by a discussion of key market trends and issues. The final section offers conclusions and observations.