This book presents the methodology and mathematical models for dual-fuel coal-gas power plants in two basic configurations: systems coupled in parallel and in series. Dual-fuel gas and steam systems, especially parallel systems, have great potential for modernizing existing combined heat and power (CHP) plants. This book presents calculations using a novel methodology applied to systems in continuous time and analyzes the impact of the investment profitability of the EU ETS (European Union Emissions Trading Scheme) derogation mechanism, which encourages enterprises to modernize existing generation units. It also includes a detailed case study of a coal power plant modernized by repowering with a gas turbine. The book is intended for researchers, market analysts, decision makers, power engineers and students.