In a high-impedance communications interface, driver energy consumption is proportional to the number of signal transitions. For signals having three or more distinct levels, it is possible for a signal driver to salvage energy from some downward signal transitions and reuse it on some subsequent upward signal transitions. To facilitate this energy-conserving behavior, communication is performed using group signaling over sets of wires using a vector signaling code, with the design and use of the vector signaling code insuring that energy availability is balanced with energy demand.