The paper investigates the fundamental limits of communication over electrical multiple-input-multiple-output (MIMO) networks in which information transmission is associated to energy exchanges. We first develop the computation of the Shannon capacity of a MIMO, wideband, frequency-dependent, time-invariant channel. This gives us the fundamental equations linking the achievable bit-rate, the needed power and its distribution over the necessary bandwidth. Such equations are then specialized to a general cascade of electrical stages and further detailed to tackle the case of a specific lumped elements circuit. With reference to such a circuit the effectiveness of the method is demonstrated by addressing simple cases which highlight the role of different kinds of coupling between electrical paths. Finally, the case of transmission over intra-chip buses realized with a real-world silicon technology is addressed, for which the effect of massive parallelism is discussed.