The authors of this journal article propose a systematic framework to estimate the impact on operating costs that are due to uncertainty and variability in renewable resources. The framework quantifies the integration costs associated with sub-hourly variability and uncertainty as well as day-ahead forecasting errors in solar photovoltaics (PV) power. A case study illustrates how changes in system operations may affect these costs for a utility in the southwestern United States (Arizona Public Service Company). The authors conduct a sensitivity analysis under different assumptions about balancing reserves, system flexibility, fuel prices and forecasting errors.