Which of the following is the MOST energy efficient way of powering equipment within a datacenter with a large UPS battery bank?

UPS battery banks inherently store and output DC power. Distributing 48V DC directly to equipment removes the need for a DC-to-AC inverter at the UPS output and the subsequent AC-to-DC rectifier inside each server power supply. Eliminating these two conversion steps - each of which dissipates heat - yields the lowest overall conversion loss and the highest end-to-end efficiency.

120V single-phase requires a full DC-to-AC inversion from the battery bank and then AC-to-DC rectification at each load, incurring conversion losses at both stages.

240V 3-phase AC reduces distribution conductor losses over distance but still requires the same two conversion stages from the DC battery bank, making it less efficient than direct DC distribution.

480V 3-phase is suited for high-power bulk distribution but also demands both DC-to-AC and AC-to-DC conversions before power reaches server-level equipment, producing greater aggregate losses than 48V DC.