In the arid southwest, water is invaluable—municipalities, agriculture, power plants, and the environment all rely on this limited resource. The economic value of water varies tremendously, depending on alternate uses, location, and scarcity of the resource, among other factors. As urban populations continue to grow and climate change reduces available supplies, the scarcity and value of water will increase. Most electric utilities and regulators do not adequately integrate water into electric resource planning. In modeling and evaluating resource plans, utilities and regulators should assess the opportunity cost of using water for power generation over the lifetime of the power plant.