Abstract If the dependence of base station output power on system parameters in a mobile network would be known, it would be possible to achieve energy savings by adjusting the output power in each channel to the current traffic demands. Since power radiated in an active channel is a random variable, so is the total output power of a base station; its calculation can be a complicated task since it involves convolution of probability density functions associated to each active channel. In this letter, we propose a simulation approach to estimate the power of active GSM connections. We apply our model to an analytically tractable scenario and show that the results match.