Advanced energy technologies span a wide variety of resources, techniques, and end-user requirements. Economic considerations are major factors that shape their harnessing and utilization. A discussion of the basic factors in the economic arena is presented, with particular emphasis on renewable energy technologies-photovoltaics, solar-thermal, wind-electric conversion, biomass utilization, hydro, and tidal and wave energy systems. The following are essential to determine appropriate energy system toplogies: proper resource-need matching with an eye on the quality of energy requirements, integrated use of several resources and technologies, and a comprehensive consideration which includes prospecting, collection, conversion, transportation, distribution, storage and reconversion, end use, and subsequent waste management aspects. A few case studies are included to appraise the reader of the status of some of the kev technologies and systems.