UPS Runtime Calculator

UPS Runtime Calculator
Battery Model
UPS Load (kVA)
Power Factor
Number of Strings
Number of Batteries in a string
Runtime in Minutes
@ 1.67 Voltage
0 minutes
Runtime in Minutes
@ 1.75 Voltage
0 minutes

How Long Does A UPS Battery Run?

When determining the ideal configuration for your Uninterruptible Power Supply (UPS) starts with understanding how long you will need back-up power before other power systems take over.


There are two or three factors to determine how long a UPS battery will last:

  • The battery capacity (AH)- The battery capacity is a measure of the charge stored in the battery, and is usually measured in Amp-hrs (AH). The battery capacity is the number of hours that the battery delivers a current at the specific battery voltage.
  • Power load of devices being supported- Each device the UPS needs to support has their own power supply requirements, which is measured in Watts (W). The sum of all these individual device power requirements adds up to the UPS’s total planned load.
  • DC Bus (V) – This is the voltage the inverter requires to operate. DC buses range from 12V (1 x battery) to 480V (40 x batteries).

How long a UPS lasts under the load is determined by its battery capacity. How much power a UPS can supply at any given time determines the battery life. Other factors that impact UPS battery life include UPS efficiency, power factor, and battery type.

Calculating UPS Battery Runtime

The UPS runtime formula is a rough estimate to figure out if the number of devices planned are able to be supported for the necessary length of time.

The UPS runtime formula calculates runtime based on the battery capacity and the UPS’s total load. UPS runtime consists of the ratio of battery capacity (AH) over the load (A) on the UPS:

Time = AH / A

Or, you can use our handy UPS Runtime Calculator

Making sure that your facility has the proper set up when it comes to back up or emergency power helps eliminate downtime, protect your critical equipment, and maintain business continuity. All of this saves you time and money!


Critical Infrastructure Group offers an array of new and used UPS for purchase or rental. Our team of specialists can guide you through the process of deciding what configuration makes the most sense for the unique needs of your business.


Reach out to the team at CI Group today!

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