Reason #1:
Utility companies

Utility power isn't clean. Mainly because it doesn't have to be. By law, it can vary widely enough to cause significant problems for your equipment.

Utility power isn't 100% reliable. In the U.S., it's 99.9 percent reliable, which translates into a likely nine hours of total downtime every year. Just from issues at the power company.

Even short outages can be trouble. Losing power for just 10 seconds can trigger events that may require 15 minutes or possibly hours to get equipment back online.

Reason #2
The problems and risks are intensifying

High-tech equipment is highly sensitive. Computing and networking components are more vulnerable than ever to power problems. As technology improves, high-density servers are doing more, which puts more at risk.

Availability is everything. If IT systems go down, the entire enterprise can't function.

Downtime is costly. Some industry estimates believe the U.S. economy loses between $200 billion and $570 billion a year as a result of outages and other disturbances.

Reason #3
Generators and surge suppressors are not enough

Generators only work when the power's off. Backup generators address outages but provide no protection from the other power disturbances.

You need more than a surge protector. Surge suppressors take care of power surges but provide no protection from under-voltage, variance conditions and other power problems.

A UPS performs three primary functions:

First, a line-interactive or Double-conversion UPS conditions the incoming dirty power from the utility company. It filters out the irregularities and gives you clean, uninterruptible power.

Second, it provides ride-through power to cover for sags or short-term outages (3 minutes to several hours, depending on what you need),

Finally, it enables seamless system shutdown during a complete power outage.

There are four different kinds of UPSs:

Standby UPSs — These smaller UPSs provide an economical source of protection from power outages, surges and sags. If you just need basic protection for small systems like desktops and cash registers, a small standby UPS like the Powerware 3105 or Pulsar Ellipse is your best choice.

Line-interactive UPSs — If you need a voltage regulation and power protection for moderate loads (500VA to 6 kVA), particularly for commercial or office applications, a line-interactive UPS like the Powerware 5125 or MGE Office Protection Systems Evolution/S is your best bet.

Double-conversion UPSs — These UPSs convert raw power coming in to refined power through a process of double conversion. They change it from dirty AC to DC, clean it and then convert it back to AC. For very sensitive, expensive equipment that needs clean, true sine-wave power, a double-conversion UPS like the Powerware 9355 or MGE Office Protection Systems Pulsar/M/MX is the smart pick.

Double-conversion On Demand — If you must have clean power for high-density data centers, and energy efficiency and flexible configuration are top priorities Eaton's innovative, hybrid Double-Conversion On-Demand (exclusive to the Powerware BladeUPS) would be the only choice. It combines line-interactive and online modes.

In a centralized UPS configuration, a larger UPS supports multiple locations or a group of equipment from a single point. Centralized UPSs are often hardwired into an electrical panelboard.

A decentralized configuration allows each UPS to protect a handful of devices or a single piece of equipment. Decentralized UPSs are usually plug and play using plugs and receptacles.