This paper aims at improving the quality of an OPF (optimal power flow) solution including power demand uncertainty. The goal is to obtain a best setting of the input which results in a performance characteristic of the output close to target with minimum variability. Here, a post-optimality procedure which incorporates the philosophy and the method of Taguchi is applied. Power demand variability is included in the analysis by means of the expected value of a loss function which is estimated by the Taguchi orthogonal arrays approach. The best and least sensitive solution over uncontrollable power system variability is selected by means of signal-to-noise ratios.The paper overviews the Taguchi approach, and illustrates the application of the method to improve the quality of an OPF involving the IEEE 14-bus network.