The demand for power in the year 2020 will be covered by a diversified power plant park in which renewable energies are the dominant element. The growing share of renewable energies will, however, change the basic structure of power production. By 2020, around two thirds of the power produced from renewable energies (189 TWh) will be generated from the fluctuating sources solar and wind.
The industry analysis shows that even under conservative assumptions there will always be sufficient secured capacity available at any time, even at for the maximum load (annual peak load).. This will be guaranteed due to the strong increase of installed capacity of power plants based on renewable energies, as well as by increased storage capacity.
A secure power supply means that at any time  power production will be sufficient to cover the actal demand. Fluctuations in demand (e.g. peaks at lunchtime) or in the available power supply (power plant failures, fluctuating wind availability and solar radiation) always need to be compensated. This is precision work and requires a constant source of available power plant capacities. The share of all power plant capacities that, from a statistical point of view, will almost certainly be available at times of maximum demand is called “secured capacity”. The difference between this and the annual peak load is called “remaining capacity”. It is practically a “buffer solution” which is available as a reserve for extreme situations (e.g. unusually cold periods), an above-average power plant failure rate and eventually as an export capacity.  

Sources: Bundesnetzagentur, AG energy balance calculations, own calculations

Germany’s current power supply system is much more flexible than is generally known. 10 gigawatts of storage and pump storage hydro power plants are available for the German grid. This equates the output of twelve coal-fired power plants. Pump storage stations accumulate power quantities at high production levels and they can supply them in a few seconds on demand. By 2020, this value will presumably increase to around 13 GW. However, the industry forecast has used a conservative estimate of only 10 GW storage capacity for the year 2020. In addition to this, the dispatchable bio-energy capacity will grow from 4 GW today to 9.3 GW.Today, the existing hydro power storage plants are primarily used for night storage of the power generated by the fossil and nuclear base load power plants which is not needed during this period. With further growth of renewable energies, the need to store the power when there are optimum wind and sunlight conditions will also be growing. Germany currently has hydro power storage plants of around 6,200 MW generation capacity and 6,000 MW pump output. In addtition, German power suppliers have property or long-term power acquisition rights to foreign pump storage power plants with around 3,400 MW capacity in Luxemburg and Austria (Vorarlberg and Tirol). These plants are connected via direct lines to the German power grid and are used for the needs of the German system. Therefore they can and must be handled as domestic systems in the capacity calculations. In combination with these, the power plant park in 2020 will be able to deliver an adequate secured capacity at any time.