A specialty in austria (in the middle of the map) is pumped-storage hydroelectricity. Since there are so many mountains and valleys, lakes are used as giant batteries. Water can be pumped up in times of excessive supply and released to produce energy when there's higher demand.

This keeps the power lines stable and compensates for factors like lack of wind in wind power stations, startup/shutdown times of thermal power plants, differing consumption patterns because of colder weather etc.