AbstractOne of the most critical problems in operation of modern power systems is static electrical load dispatch (SELD) between the energy generator units with minimum production cost. In recent years, more complete and accurate models of the problem have been presented, which made it non-linear or non-convex. For example, the input–output characteristics of power plant units are non-linear or non-convex due to existence of valve-point effect. It is a non-convex optimisation problem with some constraints, which cannot be solved using ordinary mathematical methods; it requires intelligent evolutionary optimisation methods to resolve. In this paper, a novel approach called improved exponential harmony search algorithm is presented for improving the HS algorithm to solve the SELD problem considering the valve-point effect. The numerical results show that the proposed method has better convergence and also lower production costs than the two other compared methods i.e. conventional HS and particle swarm opti...