In this work we ask: how much can we reduce the power consumption in deep-sub-micron buses using coding techniques? We answer the question in two steps. First we give the minimum energy per information bit required for communicating through deep-sub-micron buses. Then, we show that the minimum energy is asymptotically achievable using coding. In addition, a simple differential coding scheme is proposed that achieves most of the possible energy reduction. The methodology used here also applies to more general communication and computation models.