The semiconductor industry has increasingly ambitious sustainability goals. Eco efficiency goals are sometimes difficult to achieve in tandem with each other. For example, high water recovery requires more energy and chemicals. Additional energy also requires more evaporation water in the cooling towers. A modelling tool will be introduced to study scenarios to keep water and energy efficiency in balance and what impact it has on other boundary conditions. Improvements will require a different mindset in the future since potential solutions are multi-disciplinary and require cooperation of many different stake holders in the fab.