As energy plays a central role in the world development, it represents as well a major challenge for sustainable development. Today, more than 80% of the primary energy consumption is based on fossil fuels and the share is likely to remain high in the future. Even if technology developments will reduce the specific consumption, the world energy demand is likely to increase in line with its population. Energy and material efficiency and the integration of the renewable resources will therefore have to play a major role for sustainable development. The challenge concerns not only the technologies at the conversion and useful energy level, but also the energy management and infrastructures. The 2000 W per capita society initiative launched by the Board of the Swiss Institutes of Technology targets the identification of the major technological breakthroughs to reduce the per capita primary energy use of Switzerland by two-thirds within five decades. Although the study examined the energy saving potentials in the complete conversion chain “from primary energy to energy services” in the main sectors of economy: buildings, transport and industry, this presentation focuses on some of the key technologies for energy conversion and upgrading. The systems integration is of prime importance in order to valorise the exergy potential of the energy resources. Therefore methodology aspects are crucial both for design and for a coherent ranking of technology options to facilitate the discussion with decision makers. Information technology and in particular multi-objective optimization is one of the promising approaches in this respect. On the pathway to the 2000 W per capita major aspects to consider are the availability of resources in phase with the services required (both in terms of power and of energy), the degree of renewability, the environmental impacts, the social acceptance (including safety, waste storage, nuclear dissemination, etc.), the geopolitical context, the required investment needed, etc. Examples of major efforts required on the path towards a more sustainable society include more efficient heat and cold production, biomass conversion, CO2 capture and storage, high temperature technologies for hybrid fuel cell-gas turbine cogeneration units or in processes using high temperature separation membranes.