Uninterruptible Power Supplies

Choosing a UPS

The choice of UPS is a complicated process and depends on a number of factors, including:

• the type of equipment you have;
• the number and size of equipment pieces to be protected (each possibly drawing a different amount of current);
• the features you require (e.g., communication port and smart software); and
• the length of "uptime" in the event of an outage

With many sizes and types of UPSs, a buyer must carefully examine each piece of critical equipment to be protected by the UPS -- taking into account the amount of power your combined equipment will draw and the time that this equipment needs to be supported -- and work in an appropriate safety margin to accommodate growth. Several UPS manufacturers provide online guides for office equipment, server rooms and entire data centers. These guides allow you to enter your equipment types and receive recommendations for UPS sizing and type.

In addition, below are white papers that explore the different types of UPSs for data centers:

• Comparison of Static and Rotary UPSs (PDF, 1.1 MB)
• Comparison of On-Line versus Line Interactive UPSs  (PDF, 266 KB)

Helpful Hints When Purchasing a UPS for Your Computer

• Make sure that the UPS comes with software which shuts down and backs up computers.
• Make sure that the UPS includes surge protectors on input and communication lines.
• Consider an air conditioned location --battery lifetime is strongly temperature dependent and decreases by 50 percent with every 15 degrees in temperature rise.
• Make sure that the UPS performs automatic battery tests to warn whenever the batteries should be replaced.
• Consider selecting the next higher UPS size to increase backup time.

Be sure to look for the ENERGY STAR when shopping for uninterruptible power supplies

Current Specification Effective Date:  January 1, 2019

The ENERGY STAR Uninterruptible Power Supply specification establishes minimum average efficiencies for UPS battery backups with different rated output power and input dependency characteristics, such as voltage and frequency dependent (VFD), voltage independent (VI), and voltage and frequency independent (VFI). Each of these product types, as well as multi-mode and DC-output/rectifiers, have their own criteria levels, which weight the efficiency of the product by the time spent at a specified proportion of the test load. In addition, ENERGY STAR products meeting the VI and VFI definitions must also have a minimum power factor of 90%.

For a complete description of the specification, please go to Uninterruptible Power Supplies Version 2.0 Program Requirements (PDF, 980 KB).

Uninterruptible Power Supply Key Product Criteria: ENERGY STAR