There is currently 140% as much renewable power capacity seeking to connect to the U.S. electric grid as total installed capacity. This backlog may result from project interdependencies causing uncertainty over how these costs evolve. We study the interconnection queue by which projects connect to the California electric grid. We find evidence of both congestion and cost sharing between projects, and that many projects exit the queue quickly after their initial cost assessment. We embed these descriptive findings in a dynamic equilibrium model where potential projects choose to enter the queue, face interdependent costs that evolve over time, and ultimately decide whether to exit or sign a contract to connect. Counterfactuals show that removing insurance against cost reassessment increases decreases inter- connection costs 14.4%, but auctioning spare grid capacity only encourages more profitable projects to contract.