This presentation examines trends in wind plant cost of energy over the last several decades and discusses methods and examples of projections for future cost trends. First, the presentation explores cost trends for wind energy from the 1980s, where there had been an overall downward trend in wind plant energy costs. Underlying factors that influenced these trends, including turbine technology innovation for lower wind speed sites, are explored. Next, the presentation looks at projections for the future development of wind energy costs and discusses a variety of methods for establishing these projections including the use of learning curves, qualitative assessment using expert elicitation, and engineering-based analysis. A comparison of the methods is provided to explore their relative merits. Finally, a brief introduction is provided for the U.S. Department of Energy program-wide shift towards an integrative use of qualitative and quantitative methods for assessing the potential impacts of wind plant technology innovations on reducing the wind plant cost of energy.