Factor graphs are graphical models with origins in coding theory. The sum-product and the max-product algorithms, which operate by message passing on a factor graph, subsume a great variety of algorithms in coding, signal processing, and artificial intelligence. The paper aims at extending the field of possible applications to dynamical electrical networks (i.e., networks that contain capacitors and inductors as well as static components). Interestingly, the resulting factor graphs have a structure very much akin to a Kalman filter.