Earlier this month, the Columbia Grid Wind Integration Study Team released its report on the economics of developing wind resources close to load centers compared to developing wind sites in Montana and Wyoming.
In general, the study found that wind power developed locally is more economical for Northwest coastal loads because of the huge transmission costs associated with connecting remote wind generation.
The study summarizes the conclusions from a variety of other studies, including the Council's Sixth Power Plan.
For now, constructing long-distance transmission for remote wind resources doesn't appear to be cost-effective unless the transmission is relatively low-cost, short, or has additional benefits.
The research on this on ongoing, and we'll update as new information comes out.