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To save your valuable electronic devices from getting damaged due to sudden power failures or brownouts, you must install uninterruptible power supplies (UPS) for providing standby power. A UPS system is usually used to protect computers, telecommunication equipment, data centers, and other mission-critical electrical devices, that can undergo damage and data loss as a result of unexpected power disruption. There are many variables involved in the making of a UPS and as consumers, it is upon us to know them in order to purchase the right kind of system.

For determining the right backup power supply system for your electronic device, you need to consider different features, such as configuration, load type, and requirements, of the UPS. It is essential to calculate the size of the UPS before choosing the apt one for your computing device. It is also necessary to know the power drawn by electronic devices (loads) that is derived from the critical power path. This is calculated in volt-ampere (VA) and Watts.

What are KVA and KW?

Volt-ampere is referred to as the apparent power and is determined by measuring the voltage provided to the equipment multiplied by the Amperage (Amps) obtained to power it. It is drawn from the power supply to make an electronic component function. KVA is calculated by multiplying VA by 1,000 (kilo).

The power drawn by any system or device is measured in watts. Known as the ‘Real Power’, the watt is the value that the utility companies use to charge the electricity consumed per hour, and is expressed as KWh. Watt is calculated by multiplying volts and amperes and is based on direct current circuits. Kilowatt (KW) means 1,000 watts. In the case of AC circuits, the power can be expressed as watts that are obtained by multiplying volts, ampere, and power factor.

The power companies find AC far more efficient, though it shows a characteristic called reactance when it hits the transformer of the equipment.

Now, let us know about the use of kilo-volt-ampere or KVA in UPS and KW in UPS.

What is the Importance of KVA and KW in the UPS system?

The real power (watts), that is sourced from the apparent power (volt-amperes), is reduced by reactance. The ratio of volt-ampere and watt or the ratio of KVA and KW is known as the power factor (PF). Power factor can be associated with the input and output of a UPS. Input power factor refers to the load provided by the UPS on the main power supply. Most of the UPS systems today have a value of nearly 1.0 or higher than 0.9 input power factor. The higher is this value, the more accurately matched the UPS input demands to the voltage and current waveforms of the supply. This will result in more efficient power conversions, less heat emission, and less energy wastage too.

The output power factor is mainly taken into account when determining an uninterruptible power supply load. For instance, a 60KVA UPS has an output power factor of 0.8 or 0.9 pF, which indicates it can deliver a load of 48KW or 54KW. With an output power factor of 1.0, the UPS system can supply 60KW.

Most of the large, commercial UPS units are fabricated with a PF of 0.9. Majority of the recent computing technology provides a PF of the range of 0.95 to 0.98 to the UPS. Many UPS systems are designed with PF of 1.0, that implies the KVA and KW ratings are similar (100 KVA = 100 KW). But, the IT load never provides a 1.0 PF, the KVA rating will be the actual load limit for those UPS systems.

The power factor has been used by the UPS manufacturers to benefit them while they promote their systems. In case of many sub 2KVA backup power UPS supply, usually, there is a power factor less than 1.0 and even as low as 0.6 for the smallest backup systems. The UPS companies can provide a 300W UPS, that has the capacity to deliver 500VA of real power when VA or KVA in UPS is used to determine the size of the system.

However, it is also significant to check the KW in UPS, which has become a less common practice. This is more important when there is a rise in the load size. Larger UPS systems are usually rated with a higher output power factor of about 0.9. A higher output power factor of around 0.8 can be found in legacy systems. The recent uninterruptible power supplies are introduced in the market with Unit output ratings. Here, the same UPS will deliver the same KVA and KW values.


This article has informed you about how the values of KVA and KW in UPS are very crucial when you plan to buy the right standby power UPS system for your electronic device. Choose the apt UPS for smooth functioning and high longevity of your electronic devices.

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