2009 State of the Market Report
each day over all interfaces, and the deviation of real-time imports from the day-ahead imports. In the real-time market in 2009, the Midwest ISO imported an average of 3.0 GW, a slight decline from the average of 3.1 GW in 2008. PJM (1.1 GW) and Manitoba Hydro Electric Board (“MHEB”) (0.9 GW) continued to be the two largest sources of imports to the Midwest ISO in the real-time market, comprising over two-thirds of net imports.
Figure 89: Average Hourly Real-Time Imports All Hours, 2009
Difference from DA Average
3,000 2,500 2,000 1,500 1,000 500 0
Quantity in MW
6,000 5,000 4,000 3,000 2,000 1,000
Real-time net imports generally decreased from those scheduled in the day-ahead market. On 49 days, the average net imports decreased by more than 1,000 MW, which can create reliability issues that the Midwest ISO must manage. Large changes in net imports can cause the Midwest ISO to have to commit additional generation and rely more heavily on peaking resources. The figure shows changes in net imports from day-ahead to real time occurred with greater frequency in late fall and in winter. The largest shares of the reduced real-time imports are on the western interfaces with WAUE and MHEB, though all the major interfaces show reduced real-time imports.
Our next analysis shows net imports by interface to better show where the Midwest imports and exports originate. The interface between the Midwest ISO and PJM, both of which operate LMP