A system is provided for driving an implantable neurostimulator lead, the lead having an associated plurality of electrodes disposed in at least one array on the lead. The system comprises an implantable pulse generator (IPG), the IPG including an electrode driver, a load system for determining load requirements, an IPG power coupler, and an IPG communication system. The system also includes an external unit, which includes an external variable power generator, an external power coupler, an external communication system, and a controller for varying the power level of the variable power generator.