This paper proposes the Shuffled Frog Leaping Algorithm to solve the Profit Based Unit Commitment problem under a deregulated environment with emission limitations. The bi-objective optimization maximizes generation companies' profit while minimizing thermal unit emissions, satisfying all constraints. A softer demand constraint is used to allocate fixed and transitional costs to scheduled hours. IEEE 10-unit 39-bus system with 24 h data is simulated in MATLAB 7.10. Results show the algorithm achieves maximum profit and minimum emissions with reduced computational time compared to traditional unit commitment. © 2012 Elsevier Ltd. © 2013 Elsevier B.V., All rights reserved.