2009 State of the Market Report
flow over the constraint relative to its entitlement. This market-to-market process is essential for ensuring that generation is efficiently re-dispatched to manage these constraints, and that prices in the two markets are consistent.
Figure 68 summarizes the frequency that Midwest ISO market-to-market and PJM market-to- market constraints were active and binding in 2008 and 2009. The top panel represents coordinated flowgates located in the PJM system and the bottom panel represents flowgates located in the Midwest ISO. The darker shade in the stacked bars represents the total number of peak hours in the month when coordinated flowgates were active. The lighter shade represents the total for off-peak hours.
Figure 68: Market-to-Market Events 2008 – 2009
MISO Flowgate Hours Active
MISO Off-Peak MISO Peak PJM Off-Peak PJM Peak
08 09 J F M A M J J A S O N D J F M A M J J A S O N D
PJM Flowgate Hours Active
Activity on PJM market-to-market constraints decreased 31 percent from 2008 to 2009, to 916 hours per month. However, activity on Midwest ISO market-to-market constraints increased by 44 percent in 2009 to over 1,000 hours per month. The Midwest ISO market-to-market constraints that were coordinated most frequently were west-to-east constraints impacted by Commonwealth Edison exports. These constraints occurred most often during off-peak hours.