The carbon constrained design of energy supply infrastructure for new build schemes was investigated. This was considered as an optimization problem with the objective of finding the mix of on-site energy supply technologies that meet green house gas emissions targets at a minimum build cost to the developer. An integrated design tool was developed by combining a social cognitive optimisation solver, an infrastructure model and a set of analysis modules to provide the technical design, the evaluation of greenhouse gas emissions and the financial appraisal for the scheme. The integrated design tool was applied to a new build scheme in the UK with a 60% target reduction of regulated emissions. It was shown that the optimal design and corresponding cost was sensitive to the year of build completion and to the assumptions applied when determining the emissions intensity of the marginal central generators. (C) 2013 Elsevier Ltd. All rights reserved.