2009 State of the Market Report
Load and Resources
permanently derated (relative to nameplate capacity ratings) and unavailable for dispatch in any hour. This represents an increase of 1.6 GW over 2008 and is attributable to three factors: (1) the new Midwest ISO member additions of MEC and MPW; (2) aging baseload capacity that cannot operate at its nameplate rating; and (3) new wind resources that do not operate close to their nameplate ratings.9
Figure 13 illustrates the planned and forced generator outage rates in 2009 by month. The values in the figure include only full outages—they do not include the partial outages or deratings shown in the prior figure. The analysis in the figure divides the forced outages between short- term (less than seven days) and long-term (seven days or longer).
Share of Capacity
Short-Term Forced Outages
Long-Term Forced Outages
Figure 13: Generator Outage Rates 2007 – 2009
070809 J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J A S O N D
The annual combined outage rate increased in 2009 to 11.4 percent for the three categories of outage, an increase over the 2008 rate of 9.3 percent and the 2007 rate of 11.0 percent. Planned outages rose 32 percent as low load levels and prices made it more attractive to schedule
The average capacity factor of wind generation in the Midwest ISO was 27 percent in 2009.