This paper presents an overview of the Wind Deployment Systems Model (WinDS). WinDS is a multiregional, multitime-period, Geographic Information System (GIS), and linear programming model of capacity expansion in the electric sector of the United States. WinDS is designed to address the principal market issues related to the penetration of wind energy technologies into the electric sector. These principal market issues include access to and cost of transmission, and the intermittency of wind power. WinDS addresses these issues through a highly discretized regional structure, explicit accounting for the variability in wind output over time, and consideration of ancillary services requirements and costs.