Recent regulatory initiatives such as New York’s Reforming the Energy Vision (REV) or California’s Energy Storage Mandate have incentivized smaller, cleaner, and more distributed energy resource development. As part of the day-ahead market clearing process, the ISOs today have to solve a computationally intensive Security-Constrained Unit Commitment (SCUC) model. This presentation will discuss the mixed integer programming (MIP) solution challenges in dealing with many smaller resources in the large-scale day-ahead SCUC model and highlight some on-going research efforts at the NYISO.