The building sector, as one of the major energy consumers, demands most of the energy research to assess different energy options from various aspects. In this paper, two similar residential buildings, with either low or high energy consumption patterns, are chosen as case studies. For these case studies, three different renewable energy technology and three different hybrid systems are designed for a specified size. Then, the environmental impact indices, renewable energy indices, and the renewable exergy indices have been estimated for every energy options. Results obtained show that the hybrid systems (without considering the economics factors) are superior and having top indices. The importance of the energy consumption patterns in buildings are proven by the indices. By cutting the energy consumption to about 40% the environment index would increase by more than twice (2.1). Utilization of the non-fossil fuels is one part of the solution to environmental problems while energy conservation being the other. It has been shown that the re-design of the energy consumption model is less complex but more achievable for buildings. (C) 2012 Elsevier Ltd. All rights reserved.