You have been asked to provide a N+1 level of power redundancy in the new equipment room (ER) being designed with a Tier-II power supply. What should you do?

A single UPS has no redundancy - if it fails, the entire facility loses conditioned and battery-backed power, which is an N+0 (no redundancy) design.

N+1 means one additional unit beyond the minimum required, so if N=1 UPS is needed to serve the facility, one spare must be available. Two UPS units with automatic power failure transfer satisfies this by allowing either unit to carry the entire facility load - under normal operation one unit is active while the second stands by, and an automatic transfer switch seamlessly switches to the second upon failure, meeting the Tier-II redundant component requirement without a single point of failure in the UPS layer.

Two UPS units each serving only half the facility means a failure of one unit drops half the equipment, because the surviving unit is sized only for its share of the load and cannot absorb the full facility load - this does not meet N+1.

This option appears to describe a similar configuration but does not clearly specify that the second system can carry the entire facility load or that transfer is automatic, leaving the redundancy capability ambiguous and potentially insufficient for N+1 compliance.