It is true that the use of underground cables will result in higher costs. But it is also clear that, in macroeconomic terms, even if the grid is expanded using underground cables, this is still the cheapest route to a successful energy transition.
In macroeconomic terms, grid expansion which meets with local acceptance and takes place in actual fact will reduce the costs of the energy transition. At present, congestion management is causing high costs (combined costs for redispatch, feed-in management, reserve power stations). These annual costs exceeded 1 bn euros in 2015. Unless there is significant progress on grid expansion, these costs will continue to rise in the coming years.
Greater use of underground cables will cost an additional €3bn to €8 bn in investment costs (compared to the costs under the former legal situation). These are one-off investment costs which do not recur annually. These increased investment costs will be passed on in the form of grid charges.
Over, it is very difficult to arrive at a precise cost estimate in this current stage of the planning. The extent to which costs will increase due to the use of underground cables in the ultra-high voltage transmission grid will very much depend on local conditions (actual route, soil conditions, transverse infrastructure, actual cost of components, etc.).