In this paper, we propose an original method for analyzing the performance of comb-type pilot-aided channel estimation for power line communications. Our method is based on a unified mathematical decomposition of the channel estimation error, which takes both the signal-to-noise ratio of the pilot sub-carrier locations and the interpolation kernel used into account. We demonstrate that the channel estimation error is composed of two terms that evolve differently according to the pilot spacing and the interpolation technique used. The error due to additive noise over channel transmission is formulated by a simple easily used analytic expression. Our results for some practical situations show that good performances can be achieved with a simple linear interpolation.