A methodology is presented in this paper, in which the trade-offs in energy between vehicle production, operational performance and end-of-life are formulated as a mathematical problem that may be optimised. This methodology enables the consideration of the life-cycle environmental impact, through the proxy of life-cycle energy, in the very first stages of transport vehicle design where it can be concurrently balanced with other functionalities. The methodology is illustrated through a sandwich panel design case study. The optimisation results for this case demonstrate that a design solution does exist, which meets functional requirements with a minimum life-cycle energy cost. They also highlight that a pure lightweight design may result in a solution, which is sub-optimal from a life cycle point-of-view.