A bus instrument (10) configured to predictively limit power consumption and adapted for use with a two-wire instrumentation bus is provided. The bus instrument (10) includes a sensor (13), a shunt regulator (14), and a controller (20). The controller (20) is configured to generate a predicted available power Ppredicted that will be available to the bus instrument (10) after a change in the loop current IL, compare the predicted available power Ppredicted to a present time power Pt0 comprising a controller power Pcontroller plus a sensor power Psensor, and reduce the sensor power Psensor if the total available power Pavailable is less than the controller power Pcontroller plus the sensor power Psensor.