The North American electricity sector is making significant progress toward decarbonizing its power supply as solar and wind become major contributors. However, electric grid operators are increasingly challenged by the intermittent nature of these renewable energy sources. During peak demand, they are not always available. At other times, they generate too much power and cause congestion — a condition in which there is not enough capacity on transmission lines to transmit the excess power. These supply-demand imbalances affect grid reliability and cause volatile electricity prices.