A computer-implemented method is used for determining cooling requirements of a computer system enclosure, where the enclosure includes a number of installed modules, the modules including fan modules. The method includes the steps of determining an individual impedance curve of each installed module; determining fan curves for the installed fan modules; based on the individual impedance curves, determining an overall system impedance curve for the computer system; determining desired performance requirements for the computer system; based on the desired performance requirements, determining corresponding fan curves; and choosing a fan curve that intersects the system impedance curve.