Manufacturing companies consuming significant amounts of electrical energy and heat, while simultaneously possessing renewable fuel resources, are seeking the best solutions for the future. However, relatively popular ORC systems have not conquered the market in the category of small cogeneration systems. It seems that the reasons are high investment costs and relatively low efficiency of electricity production. In an effort to support the development of the Polish small and medium enterprise sector, this paper presents a proposal for a combined gas-steam system, parts of which (the steam and gas components) have already been designed at IMP PAN. The paper describes the optimization of a 1.4 MW total power combined gas-steam system for electricity and heat production, based on the Brayton cycle with an external combustion chamber and a Rankine cycle using a low-boiling point working fluid. The system is intended for a company in the timber industry, hence the fuel is wood, which is a production waste. In the Brayton gas system, the air is first compressed in a compressor to a pressure of about 3 bars and then heated in a high-temperature heat exchanger from ambient temperature to a range of 600°C-850°C. After expansion in a gas turbine to near ambient pressure, the air mixes with the exhaust gases that heat the air in the high-temperature heat exchanger. Subsequently, the exhaust gases enter a medium-temperature heat exchanger to heat the low-boiling point working fluid, which then flows into the steam turbine. This work involves the selection of optimal thermodynamic parameters for both cycles, with particular emphasis on the operating parameters of the high-temperature heat exchanger. This method of system analysis arises from the impact of the heat exchanger on the system’s capital costs and overall efficiency. The paper presents multivariate analyses of system efficiency, including the steam and gas cycles and heat demand.