Repowering a number of the state\u2019s once-through-cooled coastal power plants could supply much of the electricity needed to balance the intermittency of renewable energy supplies, according to California Independent System Operator chief executive officer Steve Berberich. He estimated that an additional 4,600 MW of power supplies with the ability to ramp up or down quickly in response to fluctuations in solar and wind energy supplies are needed. That number assumes that approximately 20,000 MW of water-cooled coastal plants, as well as a number of other 50-year old facilities in the conventional fleet, are put out to pasture. The 4,600 MW estimate could fall to about 1,600 MW with 3,000 MW of coastal power plant modernizations by 2017. Berberich said facility repowers depend largely on regulators moving from an annual resource adequacy mandate--which requires utilities to have a 15-17 percent supply cushion--to a multiyear standard. Without a multi-year commitment, generators won\u2019t be able invest in coastal plant modernizations. The focus of resource adequacy needs to shift from \u201ccapacity to capability,\u201d he added. That is, focus on power plants\u2019 ability to quickly increase or decrease their output, known as ramping, in response to surges or drops in the flow of renewable resources. The California Public Utilities Commission sets the resource adequacy rules and the grid operator is raising the issue with regulators.