BEEP stack is the supply curve for real-time energy that the ISO develops on  the basis of bids and offers.
The problem is that the plants the ISO  ultimately dispatches from the stack often conflict with the merit order  developed from the bids/offers, and the ISO has never been clear about the  decision metrics it uses to determine ultimate dispatch.
Everyone, including  Belden, thinks it can and ought to be a helluvalot more transparent.

The ISO's "BEEP" stack