This paper examines key market interaction issues between compliance and voluntary renewable energy markets. First, it provides an overview of both the compliance and voluntary markets, addressing each market’s history, purpose, size, scope, and benefits. The next section discusses the issue of whether consumer purchases of renewable energy are above and beyond mandated requirements and measures that are in place to avoid double counting. The following sections focus on supply and demand issues and the impact on renewable energy certificate (REC) prices resulting from the two markets. Finally, the paper examines the question of whether consumers will maintain interest in making voluntary purchases if RPS policies are in place.