Grid access refers to a generator’s physical connection to the larger electrical grid. In Germany, if you install a solar panel, you are guaranteed that it will be connected to the grid, and that whenever it is sunny your power will be sold on the grid (instead of it being pushed out by coal power).
One obstacle to the growth of renewables is a lack of grid access. German law specifies that renewable electricity has a priority on the grid, meaning that conventional power generators have to ramp down production. Other countries more easily allow wind turbines and solar arrays to be disconnected to protect the profitability of conventional plants.
Furthermore, German law specifies the conditions under which grid operators must expand the grid to provide a connection for wind turbines, biomass units, and solar arrays. After all, if the grid operator fails to provide the connection, investments made in renewables could come to nothing.