An integrated framework for modeling and evaluating the economic impacts of environmental dispatching and fuel switching is presented in this paper. It explores the potential for operational changes in utility commitment and dispatching to achieve least cost operation while complying to rigorous environmental standards. The work reported here employs a heuristics-guided evolutionary algorithm to solve this multiobjective constrained optimization problem, and provides the decision maker a whole range of alternatives along the Pareto-optimal frontier. Heuristics are used to ensure the feasibility of each solution, and to reduce the computation time. The capabilities of this approach are illustrated via tests on a 19-unit system. Various emission compliance strategies are considered to reveal the economic trade-offs that come into play. INTRODUCTION The main objective of unit commitment and dispatch decisions has traditionally been the minimization of system operating costs subject to co..