# How Long Will A 1500VA UPS Run? 2nd Apr, 2021

Understanding the ratings of a UPS system can be challenging for those who are novices or have limited experience of dealing with such systems. A convenient way to make things easier for them is to use real world examples so that they can see the concept in action. One common rating of a UPS is 1500VA.

Using this particular rating, we can devise a scenario which shows how long the entire UPS system would last in terms of providing backup power. Apart from the given UPS rating, we would also need information of the other components present in the system.

The additional data would include the Wattage of the load and the battery’s specifications (the Voltage and the Ah rating). The load Wattage could,for example be taken as 800W while the battery specifications could be taken as 12V 200Ah. Before making the calculations, a couple of non-idealities need to be considered as well.

The first of them is the internal inefficiencies of the UPS itself which can be adjusted through the power factor (0.8 or 0.9). The second is the avoidance of operating at the upper limit of the UPS load capacity. After making both the adjustments, a 1500VA UPS can safely handle a load of 900W which means that it is perfectly fine to use the load that we have taken in this example.

Now, to calculate how long the UPS would last for with the 800W load, the following formula would be used: (battery voltage x battery Ah rating)/ load Wattage. After calculating the values, the obtained backup time value is 3 hours. This is a subjective answer which can change if different variables are taken.

However, by taking these numbers, it has been illustrated as to how one can calculate the approximate backup time of a 1500VA UPS using 2100A batteries and an 800W load.