Through installation of sufficient storage near to the generators, a constant power output (renewables + storage) can be delivered to the grid. In such a system, the grid investments to the main grid can be minimised. A special case is a small city, neighbourhood or other sub-grid that tries to have a balanced energy supply and demand so that in case of problems the sub-grid can even be de-coupled from the main grid and be operated as an independent island grid or micro-grid.