A voltage control load center (10) includes plural modular voltage control transformer circuits (20), and is connected between supply mains (22) and a load (L) including one or more high intensity discharge (HID) lamps. The lamps are started at full line voltage, and after a sufficient operating interval ensuring that the lamps have achieved a sustaining temperature, the operating voltage applied to the lamps is reduced, effecting a considerable savings in energy use, with little or an acceptably small decrease in illumination provided by the lamps. Because the voltage control transformer circuits (20) are modular, voltage control load centers (10) suitable for a variety of differing requirements may be quickly, easily, and inexpensively fabricated and installed without the need for the conventional requirement of a custom (i.e., application specific) transformer design and fabrication, which conventional requirements are both time and labor intensive.