This page provides guidance for purchasing uninterruptible power supplies (UPSs). Federal laws and requirements mandate that agencies purchase ENERGY STAR®-certified products or Federal Energy Management Program (FEMP)-designated products for all covered product categories except as specifically exempted by law.
FEMP's acquisition guidance and ENERGY STAR efficiency requirements apply to UPS products intended for use in consumer, commercial, telecommunications (DC-output), and data center applications. UPS products that are internal to computers or other electronic devices; designed for industrial applications; part of an electric transmission or distribution system; used in mobile (e.g., marine, airborne) applications; or part of a cable television network are excluded.
This acquisition guidance was updated in December 2024.
How To Find Product Efficiency Requirements
The U.S. Environmental Protection Agency (EPA) provides UPS efficiency levels and product specification information on its ENERGY STAR website. Manufacturers meeting these requirements are allowed to display the ENERGY STAR label on complying models. Get a list of ENERGY STAR-certified UPS models here.
How To Determine Cost Effectiveness
An efficient product is cost effective when the lifetime energy savings exceed the up-front cost premium (if any) compared to a less efficient option. You can find more information about determining life cycle cost effectiveness on our general guidance page.
See Table 1 below for an example comparing the life cycle cost savings of a base model (less efficient than the ENERGY STAR required efficiency), a model meeting the ENERGY STAR efficiency and a model with the highest available efficiency.
Example: 900-W Voltage-Independent UPS
FEMP has calculated that an ENERGY STAR-certified 900-W voltage independent (VI) UPS meeting the required 98.4% efficiency level saves money if it costs no more than $36 (in 2023) more than the less efficient standard model with an efficiency of 97.3%. The best available model shown below is cost effective if it costs no more than $65 above the less efficient model (or $29 above the required model).
Table 1. Lifetime Energy Cost Savings for Efficient Voltage Independent UPS
| Model Efficiency Levels | Best Available | ENERGY STAR | Less Efficient |
|---|---|---|---|
| Average Efficiency (kWh) | 99.3% | 98.4% | 97.3% |
| Annual Energy Use (kWh) | 44 | 97 | 163 |
| Annual Energy Cost | $5 | $11 | $18 |
| Lifetime Energy Cost | $24 | $53 | $89 |
| Lifetime Energy Cost Savings | $65 | $36 | ===== |
Energy Use and Cost Assumptions
Annual Energy Use: Assumptions for the time spent at different loads for voltage-independent UPSs were based on the ENERGY STAR UPS specification. Assumed power loss values and lifetime of six years for a typical 900-W voltage-independent UPS were based on the UPS Engineering Analysis under the DOE’s Energy Conservation Standards for Uninterruptible Power Supplies (Docket EERE-2016-BT-STD-0022).
Annual Energy Cost: Calculated based on an energy price of 11¢/kWh, which is the average electricity price at federal facilities in the United States as of July 2024. Learn more about Federal Government Energy/Water Use and Emissions data.
Lifetime Energy Cost: Calculated as the sum of the discounted value of the annual energy cost over the assumed product life of 6 years. Used future electricity price trends and a 3% discount rate from the Energy Price Indices and Discount Factors for Life-Cycle Cost Analysis – 2024: Annual Supplement to NIST Handbook 135 and NBS Special Publication 709 (NISTIR 85-3273-39).
Lifetime Energy Cost Savings: The difference between the lifetime energy cost of the identified models.
Model Efficiency Levels
Best Available: Based on the model data from DOE’s UPS Engineering Analysis most closely aligning with the best-in-class efficiency reported in ENERGY STAR®’s certified products list for UPSs. More efficient models may have entered the market after FEMP's acquisition guidance was created.
ENERGY STAR: Based on the ENERGY STAR required efficiency level as of December 2024. Federal agencies must purchase products that meet or exceed ENERGY STAR efficiency levels.
Less Efficient: Based on the least efficient product that meets the minimum efficiency required for products to be sold on the market (10 CFR Part 430), which is the minimum efficiency all manufacturers need to comply with. Note energy savings will vary depending on actual usage.
Where To Buy Compliant Products
Buyers can make sure the product they purchase will be compliant by incorporating federal acquisition regulation language into contracts. Compliant products can also be found using federal supply sources and product codes. See our general guidance page for more details on buying compliant energy-using products.
Uninterruptible Power Supplies Product Codes
Purchasers can use a United Nations Standard Products and Services Code (UNSPSC) to identify and buy products and to track purchases.
The UNSPSC for UPS is 39121011.
Other Tips for Choosing and Using the Best Product Efficiently
Choosing Between VFD, VI and VFI UPSs
Voltage and frequency dependent (VFD), voltage independent (VI), and voltage frequency independent (VFI) UPS systems offer different levels of power conditioning. VFD models provide the most basic level of protection, while VFI models offer the highest level of protection for downstream equipment; the protection function of VI models fall between that of VFD and VFI. Higher levels of power conditioning generally result in lower UPS system efficiency, so choose the lowest level of protection needed for your application.
Finding the Best UPS System For Your Application
When selecting a UPS for your downstream equipment, consider equipment type, capacity, and number; the level of power conditioning required; redundancy; and the length of uptime required in the event of an outage.
Look for models that are efficient through most of the design range and that allow power usage data collection. The efficiency of UPS systems varies with loading; typically the more highly loaded they are, the more efficient. Lightly loaded systems could be losing a large fraction of the input energy intended for the equipment downstream. For systems that are constantly operated below design conditions, consider a modular UPS system to accommodate partial-load conditions and future growth.
Also consider using modular UPS systems in applications where future growth is expected, such as data centers, since they can expand in proportion with the load. Purchasing efficient UPS products for data centers can be an important step in meeting data center energy reduction goals. Agencies should consult the Center of Expertise for Energy Efficiency in Data Centers website, which includes design strategies, tools, and best practices for reducing energy use in data centers.
Tips for Using UPSs More Efficiently
When using multi-normal-mode UPS systems, consider switching to lower energy-consuming modes during operations for which the highest level of protection is not required. Check the UPS periodically to ensure battery and capacitor parts are maintained per manufacturers' instructions.