Book excerpt: Electric Utility Resource Planning: Past, Present and Future covers the balance of renewable costs, energy storage, and flexible backstop mechanisms needed in electric utility resource planning. In addition, it covers the optimization of planning methodologies and market design. The book argues that net load, ramping and volatility concerns associated with renewables call into question the validity of almost a century of planning approaches. Finally, it suggests that accounting for flexibility helps optimize the efficiency of the entire fleet of assets, minimizing costs and CO2 generation simultaneously, concluding that a flexible, independent backstop mechanism is needed, regardless of renewables or storage. Case studies provide a mix of hypothetical "what if" scenarios and analyses of real-life utility portfolios drawn from international examples.