The control areas are subdivided into balance responsible perimeters or balancing groups. Balancing groups are virtual energy volume accounts that allow electricity market players to balance their actual feed-in and offtake within a control area. Here, management of the balancing groups is the responsibility of the Access Responsible Parties (ARP).
The access responsible parties and 50Hertz sign the standard balancing group contract provided by the Federal Network Agency to manage the balancing groups. The standard balancing group contract is used to make contracts for all business transactions, such as trading, supply and grid activities. This contract includes all relevant obligations to be fulfilled by the contract parties up until the settlement of the control power used.
To ensure proper management, access responsible parties have to present their forecasts for feed-in and offtake to the transmission system operator in the form a schedule. The differences between the feed-in based on the offtake forecast inside the balancing group and the actual offtake by the ARP's customers within the same balancing group are compensated with control power.
50Hertz settles the control power used with the Access Responsible Parties each month, in accordance with the rules set up by the Federal Network Agency (MaBiS - market rules for balancing group settlement for electricity).