The 2018 Renewable Energy Grid Integration Data Book identifies the status and key trends of renewable energy grid integration in a highly visual format. This biennial data book is intended to provide an overview of selected grid integration metrics that reflect recent changes to the operation and composition of the power system as variable renewable energy (VRE) sources increase their shares of electricity supply. These grid integration metrics indicate how much VRE is currently being integrated onto the grid and highlight factors that may increase or decrease the challenges associated with integrating VRE generation onto the grid. The data and content presented focus on 2018. Some historical data and content are included to provide context for the broader electric sector and market environment for VRE integration.