Many states within the U.S., and many countries across the world, are opening their electricity markets to competition. Many others are uncertain about their plans. These differences emphasize the complexities involved in the technology and regulatory structure of the electricity industry -- an industry for which the introduction of market competition has been notoriously difficult. In response to these challenges, Alternating Currents provides a timely overview and analysis of the concerns facing industry regulators, legislators, and others as they consider whether, when, and how to open electricity markets.