A 400 Volt HPS lamp is much more efficient than a standard HPS lamp. Both systems consume 750 Watts and therefore cost exactly the same to run but the Pro HPS lamps run at a higher voltage and a lower current. 400 Volt Pro HPS lamps produce more light for the same power consumption and will give at least 10% higher yield compared to even the best standard HPS systems. In fact, when they are seen side-by-side, the HPS Pro lamps are noticeably brighter, run cooler and the light they produce is slightly whiter. So in addition to them giving a higher yield, plants grown under a 400 Volt Pro HPS are healthier, happier and are at less risk of heat damage too. The way that the system works is that UK mains power (230 Volts) is fed directly to the combined ballast and reflector via a standard mains power lead. The special ballast then converts the mains electricity to drive the special double ended 400 Volt / 750 Watt EL lamp.