Top 10 Difference Between Online UPS and OffLine UPS

Difference Between Online UPS and OffLine UPS:

UPS is a heart of the IT world and UPS is a short form of Uninterrupted power supply. Each and every computer will be connected with the UPS device. Because of all the electronics devices cannot be connected in directly to the AC raw power source. Generally, UPS are doing two major work in our electrical system. One is Feeding power to the load without interruption, and another one is protecting electronics equipment from various AC Power fluctuation. These UPS are categorized into two types, one is On-line UPS and another one is off-line UPS. In this article, we are going to study about the difference between online UPS and Off Line UPS.

Note: The direct input power supply is called as raw power supply.

On-Line UPS:

Online UPS Block diagram

See the block diagram of online UPS. Here you can see that, the input power reaches to the output circuit after changing three state such as AC to DC, DC to battery, and battery to output AC. In this, the battery source must be connected in line. The output circuit will be charged from the battery power and the battery will be in continues charging state. The best example for on line ups is your laptop. In laptop, there is a battery, and you can switch on the computer laptop even without connecting power source. However, our use might be, our device gets power only from the charging or charged battery connected to the main power supply. The important feature in online ups is, you never get power interruption until your battery drain out.

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Offline UPS:

Offline UPS working

Another mostly used ups are off line UPS, they are functionally same like online UPS. Under Normal condition the raw power supply will be connected to the load, but they feed the power to load, when there is an interruption of AC raw power supply. It needs some switching delay for delivering power to the load, but the delay can be manageable. One of the best examples for offline UPS is the desktop computers, that we use at our homes or office. Those computers have a separate UPS unit and it supplies power to the computer in the case of power failures. The only required measure is the switching delay. An offline UPS said to work better if it’s capable of doing the switch in lesser time. Also offline UPS come to the line when there is a fluctuation in the input raw power. They are efficient than off line UPS.

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Difference Between Online UPS and OFF line UPS:


Offline UPS consist of battery charger, battery, Inverter unit. Online UPS consist of AC to DC converter, battery, Inverter unit. Offline UPS the battery charger will be in smaller size, typically 10% of the full load capacity of the Single unit. But In Online UPS the battery charger designed to carry entire load of the UPS unit. Since the power loss will be in high.


See the picture of both online ups and offline ups, here online ups feed the power to the load through AC to DC converter, battery, Inverter and jointly they create a series unit. But offline UPS feed the power only absence of input power supply.

Battery Usage:

High battery usage in Online UPS and Low battery usage in online UPS.

Input Power Synchronization:

Offline UPS are designed to operate with raw input power supply during under voltage. But On line UPS never operate with input power supply, we just give the raw supply to the input terminal and the unit output will be given to the load.

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Online UPS are consisting of high cost, but offline UPS are very low cost. Typically, online ups costs two times of the offline UPS. We take an example of 1kVA UPS. See the price of Offline UPS and ON Line UPS.

UPS price


The online UPS uses highly stable parts and delivers a fixed and stable output all the times, In the case of offline UPS, the output is not stable and it varies within a specified range.


Working Temperature:

Online UPS will be loaded all time since it needs special cooling arrangement, but offline UPS does not rise it temperature, since they do not need special cooling arrangement.


High Performance of Online UPS, Low performance in offline UPS.

Voltage distortion:

Online UPS: Voltage distortion does not reduce the performance.

Offline UPS: The more the voltage fluctuations, the more the offline UPS is used. A frequent switch could lead to switching delays or could ultimately reduce its performance.

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When To use:

Online UPS: There is in frequent high voltage fluctuation, where we need to install online UPS

Offline UPS:  Use it when you are much concerned about the cost and when you wish a lower operating temperature.


Online UPS and Offline UPS Video Explanation in Hindi:


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