The wind power industry is in an era of substantial growth, both globally and in the United States. With the market evolving at such a rapid pace, keeping up with trends in the marketplace has become increasingly difficult. Yet, the need for timely, objective information on the industry and its progress has never been greater. This report—the first in what is envisioned to be an ongoing annual series—attempts to fill this need by providing a detailed overview of developments and trends in the U.S. wind power market, with a particular focus on 2006. The report begins with an overview of key wind development and installation-related trends, including trends in capacity growth, turbine make and model, and among developers, project owners, and power purchasers. It then reviews the price of wind power in the market, and how those prices compare to wholesale power prices. The report then turns to a review of trends in installed wind project costs, wind turbine transaction prices, project performance, and operations and maintenance expenses. Finally, the report examines other factors impacting the domestic wind power market, including grid integration costs, transmission issues, and policy drivers. The report concludes with a brief preview of possible developments in 2007. A note on scope: This report concentrates on larger scale wind applications, defined here as individual turbines or projects that exceed 50 kW in size. The U.S. wind power sector is multifaceted, and also includes smaller, customer-sited wind applications used to power the needs of residences, farms, and businesses. Data on these applications, if they are less than 50 kW in size, are not included here. Much of the data included in this report were compiled by Berkeley Lab in multiple databases that contain historical information on wind power purchase prices, capital costs, turbine transaction prices, project performance, and O&M costs for many of the wind projects in the United States. The information included in these databases comes from a variety of sources (see the Appendix), and in many cases represents only a sample of actual wind projects installed in the U.S. As such, we caution that the data are not always comprehensive or of equal quality, so emphasis should be placed on overall trends in the data, rather than individual data-points. Finally, each section of this document focuses on historical market data or information, with an emphasis on 2006; we do not seek to forecast future trends.