This study aims to shed light on the question of how the renewable coverage ratio and the corresponding share of usable energy from fluctuating production by photovoltaics (PV) and wind depends on the flexibility of the conventional power plant system, additional positive load options (i.e., power to heat), and storage capacity in the German electricity system. It was shown that a flexible power plant system with a small amount of must-run base generation improves the ratio of renewable coverage and usable fluctuating production significantly. Flexible loads also proved to be a very effective measure for integrating renewables into the grid. The simulation suggested that large storage systems are only effective in combination with high penetration levels of PV and wind capacity. Furthermore the ratio of PV/wind capacity that yields the highest technical efficiency was evaluated regarding the ratio of renewable coverage to usable fluctuating energy for the different scenarios.