Abstract: A gas expander based power plant system for generating electricity at a pressure reducing station of a gas transmission pipeline is disclosed where gas at high pressure is being delivered to the distribution or gas utilization system; by means of pressure reduction with a gas expander system capable of accommodating fluctuating high pressure gas conditions and maintaining desired lower pressure gas conditions, which comprise the steps of generating steam, condensing the steam in a heat exchanger and using the heat of condensation of the steam to heat a portion of high pressure gas in a controlled manner to maintain the required gas conditions of the lower pressure line throughout the range of operation, and passing the high pressure gas through a gas expander to drive an electrical generator.