The early building design phases play crucial role for the determination of building's life cycle performance in terms of resources and energy consumption and development of LCC (life cycle costs). In this stage the optimization potential is still very large, at very low cost. In the latter planning phases the change possibility rapidly decreases with simultaneously increasing costs. The investors and planners are increasingly requiring design tools as decision support instruments, which would enable simulation and optimization of LCC already in the early planning phases. This paper will present a comparative study of three commercial software-tools for LCC-calculation, and test their fitness for the implementation in the early design phases. Using a Case Study of an energy efficient building, LCC were assessed employing the three tools and the deviations of the results were compared. The analysis showed, that the tested tools cannot be employed in the early design phases without adoption and customization, lacking of benchmarks and extensive data representing the largest problem for a reliable LCC calculation and optimization. In further step, a strategy for investors for the assessment of LCC in the architectural competitions as decision support was developed and verified on a real-life project. (C) 2015 Elsevier Ltd. All rights reserved.