The capricious renewables are a problem, especially for network operators. “Compared to hydroelectric power or fossil power sources such as gas and coal, wind power, for example, has a very large statistical forecast error of five percent on average,” explains Hövelhaus. In simple words: The 100 megawatts of wind power forecast for the coming day, which are traded on the Leipzig Stock Exchange, can become 105 at any time – or just 95. However, the grid operators need predictable power in order to keep the frequency and voltage in their grids stable. If that doesn’t work, control reserve power plants have to start up, usually using expensive gas. If even that isn’t enough, the load has to be shed, as it is called in jargon: Some consumers get less power for a few hours. “That’s why the network operators have to compensate for renewable electricity if it is not certain that it can cover the acute demand 100 percent,” explains Hövelhaus. However, if the renewable electricity can be fed in flexibly, this has a major effect: Because the network operators can compensate for the five percent forecast error at any time with the electricity from the flexible biogas, they can purchase many more renewables and integrate them into the electricity system. This relieves the grids and saves CO.