Sustainable energy technologies are frequently considered for use with buildings in order to reduce their environmental impact. However, each technology will come with its own associated embodied carbon, which might potentially represent a significant proportion of a building's total embodied carbon impact. There is a need for further studies on the embodied carbon or CO2 equivalent (CO(2)e) impact of sustainable energy technologies and it is important to understand how they contribute to the total CO(2)e budget of a building. Life Cycle Assessment (LCA) is used for the CO(2)e calculations and this paper has reviewed a significant number of existing studies. The results show that LCA methodologies can and do present information which has a significant degree of inaccuracy. Furthermore, the impact of some technologies can significantly increase the embodied CO(2)e impact of modern low to zero energy buildings. Considering the whole life CO(2)e impact of each aspect of a building is crucial for the successful creation of a truly low to zero carbon building. Many current studies omit the CO(2)e impact from sustainable energy technologies. This leads to results which are under representative and misleading. (C) 2018 The Authors. Published by Elsevier B.V.