Why are we planning for a deficient system?

For a long time, using the current planning reserve margin to plan for the future system was adequate when almost all resources were dispatchable. But now that most electrical systems have fewer dispatchable resources and more energy limited resources, using the same reserve margin results in a plan that is no longer has the 1 in 10-year reliability standard.

The question then becomes one of what needs to be done in order to not develop a plan that is deficient. This requires an iterative process that includes forecasts of how the system will evolve, including the impact on ELCCs and checking to see if that resource plan meets the reliability standard. If it doesn’t, the plan needs to increase in reliability serving MWs in order to meet the reliability standard. This step wise process can be continued to develop a reserve margin requirement curve that the IRP models can then plan to so that resource plan coming out of the model isn’t deficient in a few short years.