A printer can anticipate the power needs of a print head. The printer receives a print job and a measurement of print density as a function of time for the print job from a printer driver that determines print density as a function of time based on data representing the print job. The printer includes a processor for receiving a print job, a print head and a power system for supplying power to said print head. The processor controls a voltage applied by the power system to the print head in accordance with the measurement of print density.