Congestion is the situation where the demand for transmission of electricity exceeds the available transmission capacity. Thus, there is a shortage of transmission capacity on the electricity grid. Congestion is also called transmission scarcity or shortage of transmission capacity.

If this is structural, the grid operator will increase the capacity of the electricity grid or expand the grid. This process takes several years. In the meantime, the grid operator tries to prevent and/or reduce congestion in the grid through innovative methods. One such innovative method is GOPACS.