It is the objective of this contribution to define the calculable, rea
lly available output of a fluctuating electricity generation from wind
energy and solar radiation. Apart from that, the methods for determin
ing the really available output are explained, as far as they are nece
ssary for understanding the definitions. Exemplified on a simulated la
rge-scale regenerative electricity generation in Germany, in addition,
some defined values are calculated and discussed.