A system, method and computer program for configuring power supply apparatus to supply a voltage optimized to tolerate a range about a nominal operating voltage of a device comprises a tester to test and communicate to a comparator a present utility voltage value. The comparator compares the present utility voltage with a present nominal operating voltage of the device. A configurator responds to the present utility voltage falling within an upper half of a first range having a centre point higher than the present nominal operating voltage and lower than an upper out-of-tolerance voltage of the device or within a lower half of a second range having a centre point lower than the present nominal operating voltage and higher than a lower out-of-tolerance voltage of the device, by configuring the power supply apparatus to supply a voltage respectively within the first range or the second range.