To calculate UPS Runtime,you need a certain formula. But before discussing the calculation formula, we would like to introduce the key elements involved in this formula, which are the elements that should be considered when measuring the UPS running time. 

The backup time of a UPS depends on the power of the UPS (Power consumption), the power of the load，and the capacity of the battery. (However, It has nothing to do with the rating of the Uninterruptible Power Supply.) It is reasonable to believe that the smaller the load power is, the longer the backup time it will be; correspondingly, When the load power is constant, the larger the capacity of the battery is, the longer the time will be. 

For example,If the power requirement is 1000W, then a 1500W rated unit with 12 battery blocks will deliver more runtime than a 3000W unit with 6 battery blocks.  So in order to get the longest amount of runtime for your given application, the best solution is not necessarily to opt for the highest powered UPS within your budget, but to opt for an extended run UPS System that meets your load requirements and add in batteries to support it.

After knowing these,you will easy to understand the formula for calculating the UPS backup time. 

Although there is rarely a 100% efficiency factor when connecting the battery to the device, the following formula will be based on this situation:

The formula commonly used is 10 times the capacity of the battery (in ampere hours) divided by the load of the device (in watts). The formula can be found on the label of the lead-acid battery.

If you are using the device for a long time through the battery unit, it is recommended to charge the battery regularly. Because it will shorten the life of the battery if you operate the battery until the battery is exhausted.

You can also find UPS Runtime Calculator online to help you quickly calculate the UPS backup time. It's free. Or you can e-mail sales@kstar.com and ask for help.