The Polish energy-system needs intensive investments in new technologies, which are energy efficient, clean and cost effective. Since the early 1990s, the Polish economy has had practically full access to modern technological devices, equipment and technologies. Introducing new technologies is a difficult task for project teams, constructors and investors. The author presents a set of principles for project teams useful in planning and energy modernisation. Several essential features are discussed: Energy-efficient appliances and systems; Choice of energy carriers, media and fuels; Optimal tariffs, maximum power and installed power; Intelligent, integrated, steering systems; Waste-energy recovery; Renewable-energy recovery. In practice there are several difficulties connected with planning and realising good technological and economic solutions. The author presents his own experiences of energy-system modernisation of industrial processes and building new objects. (C) 2003 Published by Elsevier Ltd.