> So congestion revenues are essentially arbitrage?

There are significant capital costs to moving power. As I understand it, an example within the US is the relationship between the regional transmission operator (RTO) SPP and MISO, who have overlapping territory. In order for move power between certain areas of SPP, it travels over MISO lines. This eats into MISO capacity. As a result the two RTOs are working on a joint project.

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