Energy consumption in an IT environment can be divided into two ie demand side or supply side. Demand‐side systems—which include processors, server power supplies, other server components, storage, and communication equipment—account for 52% of total consumption. Supply‐ side systems include the UPS, power distribution, cooling, lighting, and building switchgear, and account for 48% of consumption. The supply‐side equipment is not an independent consumer of power; its power consumption depends on the power demand
Between the incoming utility feed and IT equipment is a “power chain” of several components, each one contributing to energy loss to some extent. It is almost unimaginable to find critical IT equipment like servers powered directly from utility power or generators. Power typically passes through various equipment for power assurance and efficient distribution at the required voltage through the rack and enclosures. These would include, UPSs, PDUs, switchgear, panels, etc
Whereas PDUs typically operate at the high efficiency of 94 to 98 percent, UPSs on the other hand operate at lower efficiency and therefore the efficiency of the power infrastructure is primarily dictated by power-conversion efficiency in the UPS.