The quotation, in the graphic above, is taken from page 28 of the 2011 Executive Summary of the Eastern Wind Integration and Transmission Study. In full;
"With large balancing areas and fully developed regional markets, the cost of integration for all scenarios is about $5 (US$ 2009) per megawatt-hour (MWh) of wind, or about $0.005 per kilowatt-hour (kWh) of electricity used by customers."
The Eastern Renewable Generation Integration Study (ERGIS) is a follow-on study to the Eastern Wind Integration and Transmission Study, the Western Wind and Solar Integration Study Phase 1, and other analyses. It is a multi-year U.S. Department of Energy-funded research project designed to simulate operations of the largest power system in the world with high penetrations (up to 30 percent) of wind and solar generation.