The entire US power grid commits generators and dispatches them using MIP solvers. This is a pretty enormous problem with hard time constraints. We're talking a

The entire US power grid commits generators and dispatches them using MIP solvers. This is a pretty enormous problem with hard time constraints. We're talking about millions of constraints. Edit: well to be more specific, commitment is done with MIP solvers (difficult problem) and dispatch is done with LP solvers (easy and fast).