both of these aspects have important beneficial consequences for the whole electrical system by lowering this maximal imbalance one reduces the additional residual capacity needed in the system to balance demand in france seasonal fleet management reduces the maximal residual demand by gw from to gw based on eurelectricvgb data ieanea in france the overnight investment cost of an additional capacity of gw can be estimated at usd billion if coal plants are built coal and at usd billion for gasfuelled units