Transmission capacity is the available capacity expressed in terms of power to move electricity or gas through the electricity grid or gas grid at a single point in time, for example, from a production site such as a wind farm to an industrial site. Electricity is transported through cables and natural gas through pipes. This transportation is provided by the grid operators.
When the transportation demand for electricity and/or gas is greater than the capacity of the grid can handle, we speak of transportation scarcity or congestion.