By three years after the entry into force of this Regulation, all TSOs shall apply the imbalance settlement period of 15 minutes in all scheduling areas while ensuring that all boundaries of market time unit shall coincide with boundaries of the imbalance settlement period.

The TSOs of a synchronous area may jointly request an exemption from the requirement laid down in paragraph 1.

Where the relevant regulatory authorities of a synchronous area grant an exemption from the requirement laid down in paragraph 1 upon a joint request of the TSOs in the concerned synchronous area or at their own initiative, they shall perform, in cooperation with the Agency and at least every three years, a cost-benefit analysis concerning the harmonisation of the imbalance settlement period within and between synchronous areas.