This paper discusses key results that had emerged at the time from two studies, the Western Wind and Solar Integration Study (covers the footprint of WestConnect, a group of transmission owners that covers most of Colorado, New Mexico, Arizona, Nevada, and Wyoming) and the Eastern Wind Integration and Transmission Study (covers a large part of the Eastern Interconnection). Results from both studies showed that high wind penetrations could be successfully integrated into the power system, but were dependant on sufficient transmission and significant changes in operations.