Uninterruptible power source (UPS) is an electrical apparatus that provides emergency power to a load when the input power source or mains power fails. Online UPS differs from an auxiliary or emergency power system or standby generator in that it will provide near-instantaneous protection from input power interruptions, by supplying energy stored in batteries, supercapacitors, or flywheels. The on-battery run-time of most uninterruptible power sources is relatively short (only a few minutes) but sufficient to start a standby power source or properly shut down the protected equipment. It is a type of continual power system.
What is Offline UPS?
The Offline UPS need not finds its usage often.Yes, in this case, the electronic device gets power directly from the main AC power supply and not from the UPS. When there is any voltage surge or fluctuation in the main input power, then the offline UPS supplies power to the electronic devices. Therefore, these kinds of UPSs are required only during power failures and not all the time. 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.
What is Online UPS?
The online UPS is connected to the main load at all the time or until the battery in it gets charged. In this case, our electronic device gets the power from the online UPS and not directly from the AC main supply. So, even when the main AC fails, our electronic device’s operations need not be stopped. One such good example for online UPS is the Laptops.
What are the differences?
The Input
The online UPS gets the direct AC power supply to it and in turn, it uses the AC-DC inverter power to the electronic device. The offline UPS gets the AC power supply and gets charged but the charged AC-DC inverter power is utilized only when there is a power failure.
Operating Temperature
The online UPS renders power to the electronic devices whenever those devices are switched on. Yes, it gets charged and then supplies the power to the devices. It means that it has to work more time and so is the operating temperature. But the offline UPS on the hand comes into picture only during power failures.
Parts Used
The Online UPS, in order to maintain its frequency of operations and a continuous power to the electronic device, it requires numerous parts. Each part is chosen to ensure the reliability of operations. Those parts should also be chosen with a caution as it had to with stand the higher operating temperatures. In the case of offline UPS, the operating time is really lesser and hence the parts could also be chosen so. These parts never heat up often and hence such kinds of parts are enough to be placed. Also only during extreme conditions such as prolonged power failures, it needs its operations for a longer duration.
Cost
The number of parts in online UPS requires more cost for its set up. On the other hand, the offline UPS requires lesser cost as it involves only fewer parts in it. So if you are much concerned about the cost of set up, then offline UPS is the better choice.
Battery Usage
The online UPS uses its battery throughout the time when the electronic device is in use whereas the offline UPS is not so. It never uses the battery until there is a power failure. Therefore, we rarely use the battery in the case of offline UPS and we always use the battery in the case of online UPS.
Extreme Voltage Distortion
When there are extreme voltage fluctuations in the main power supply, the offline UPS needs to come into the picture. A frequent switch could lead to switching delays or could ultimately reduce its performance. But the online UPS is designed to handle such extreme voltage fluctuations and therefore, such conditions are expected ones here. As the online UPS is always in operation irrespective of the voltage fluctuations of the main power, there is nothing to worry about it.
Output
The output from an online UPS remains stable and almost fixed to a particular frequency. But the output from an offline UPS varies significantly within a range. Whenever you need a fixed and stable output, just for the online UPS otherwise, just go ahead with the offline UPS.
Reliability
The online UPS uses highly stable parts and delivers a fixed and stable output all the times. But the associated temperature issues are higher here. In the case of offline UPS, the output is not stable and it varies within a specified range. But the associated temperature is also based on the usage time. When you use the UPS for a longer time, the offline UPS could render a reliable service whereas an online UPS could not render such a service in this scenario.
Let us look at the differences in a tabular form below.
| S.No | Differences in | Online UPS | Offline UPS |
| 1. | The Input | It gets the direct AC power supply to it and in turn, it uses the AC-DC inverter power to the electronic device. | It gets the AC power supply and gets charged but the charged AC-DC inverter power is utilized only when there is a power failure. |
| 2. | Operating Temperature | It renders power to the electronic devices whenever those devices are switched on. Yes, it gets charged and then supplies the power to the devices. It means that it has to work more time and so is the operating temperature. | It comes into picture only during power failures. So, the operating temperatures are not always higher and it gets heated only when used for more time. |
| 3. | Parts Used | In order to maintain its frequency of operations and a continuous power to the electronic device, it requires numerous parts. Those parts should also be chosen with a caution as it had to with stand the higher operating temperatures. | The operating time is really lesser and hence the parts could also be chosen so. These parts never heat up often and hence such kinds of parts are enough to be placed. Also only during extreme conditions such as prolonged power failures, it needs its operations for a longer duration. Hence, there is no need to be very much cautious about the parts as they are hardly utilized for longer hours. |
| 4. | Cost | The number of parts used here requires more cost for its set up. | It requires lesser cost as it involves only fewer parts in it. |
| 5. | Battery Usage | It uses its battery throughout the time when the electronic device is in use. Therefore the battery is always used here. | It never uses the battery until there is a power failure. Therefore the battery is rarely used here. |
| 6. | Extreme Voltage Distortion | As it is designed to handle such extreme voltage fluctuations and such conditions are expected ones here. As the online UPS is always in operation irrespective of the voltage fluctuations of the main power, there is nothing to worry about it. | 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. |
| 7. | Output | It remains stable and almost fixed to a particular frequency. | It varies significantly within a range. |
| 8. | Reliability | When you use the UPS for a longer time, it renders unreliable service. | It renders reliable service because of fewer parts used and the lesser operating temperature. |
| 9. | When to use? | Use it when you need a UPS for a longer duration of time and the main power supply fluctuates drastically. | Use it when you are much concerned about the cost and when you wish a lower operating temperature. |
