Three large Investor Owned Utilities (IOU) have successfully integrated distributed energy resources (DER) into their grids. These utilities have integrated solar panels, batteries and electric vehicles and have developed process and procedures to ensure grid reliability. PG&E has over 400,000 behind-the-meter DERs, Hawaii Electric has a 100% renewable target, and SCE has developed a Grid Modernization program that includes a set of tools to automate and reduce the amount of manual operations. This session will review the strategies and lessons learned that these utilities undertook to successfully integrate DER.