FCiani@nyiso.com writes to the NYISO_TECH_EXCHANGE Discussion List:

Dear Market Participants,

One of the Generation Issues objectives deployed in September was to allow
off-dispatch units to move in response to price signals.  A settlement
feature of this change was that off-dispatch units would not receive bid
production cost guarantees for incremental energy.  These units would only
be guaranteed cost recovery for minimum generation and start-up costs.

The function to limit this cost recovery was incorrectly designed, with the
result that the cost recovery was not limited to the bid minimum generation
cost.  The cost recovery was incorrectly calculated as the bid minimum
generation MW  times the bid minimum generation cost.

This error has been corrected and will be reflected in the next execution
of the September settlement statements, which will correct the values
before the September invoicing period.

If you have any questions, please call Customer Relations at 518-356-6060.

Regards,

Customer Relations