This paper has the intention of discussing about a recently published paper by M.T. Hagh et al. (2014). In the discussed paper the combined heat and power economic dispatch (CHPED) problem solved by applying an improved group search algorithm. To show the performance of the algorithm, three large scale test systems were simulated. In modelling, consideration of both valve point effect and prohibited zones in the operation of power units distinguishes discussed paper from earlier works. However, there are some errors in the reported results. This discussion clarifies calculations and presents corrigendum to the results. (C) 2015 Elsevier Ltd. All rights reserved.