A confluence of factors—environmental regulation that will increase the cost of coal-fired generation; substantial underutilized natural gas-fired generation; and the mandated expansion of renewable generation—has created a historic opportunity to replace much of the obsolete coal-fired generation fleet with natural gas-fired, renewable and demand-side resources. Further extending the life of existing coal plants, moreover, will impede the flexibility needed to integrate more renewable generation and substantially reduce emissions of CO2 and local pollutants.