Difference Between Online UPS And Offline UPS (With Table)

John J. Hamlet was the first person to patent his first UPS in 1934. UPS stands for Uninterruptible Power Supply.

Every electronic device like the computer had this electronic device named UPS. This electronic equipment, UPS, provides power backup to different apparatus. This equipment’s primary work is to free the load of internal electrical problems. 

Online UPS and offline UPS are two modes of operations in any converter system that is connected to the main power line or grid and the main difference also lies in the functionality of these modes.

Online UPS vs Offline UPS

The difference between online UPS and Offline UPS is that in the online UPS the electrical power which is supplied is converted into direct current or DC through a rectifier circuit. In the offline UPS, the electrical power is run through the different special circuits that are specifically designed to filter out the electrical problems.

The latest power system technology is the online UPS, which is based on the IGBT architecture (Insulated Gate Bipolar Transistor), which offers pure sine wave electricity. These are soundless and do not make any form of noise. These UPS are used to handle high-capacity loads because they provide the most durable power.

Line Interactive UPS is another name for Offline UPS. These are modest UPS because they are often used with a single computer and give 10–15 minutes of power backup. It’s necessary when you only need a small amount of power. It has a MOSFET (Metal Oxide Semi-Field Effects Transistors) architecture, which means it has a small number of components.

Comparison Table Between Online UPS And Offline UPS

Parameters of ComparisonOnline UPSOffline UPS
Power TransferTransfers through an inverter circuit and rectifier when the AC power is availableThe power is transferred directly when the power supply is unavailable
Transfer TimeZero 5-8 milliseconds
EfficiencyLess efficientMore efficient
On ModeAlways in on modeOnly when there is the unavailability of power supply
ComponentsThe component requirements are highThe component requirements are low

What is Online UPS?

The term “online” refers to the state of the converter when there is electricity in the line. 

A stage between the load and the mains is called an online UPS. Because this system only operates when the primary power supply is present, it prevents voltage distortion in the load voltage. 

Protects sensitive loads from voltage fluctuations as well. In the event of a power outage, this UPS system offers adequate reactive power support to keep the required reactive power at the common coupling point.

The inverter is always active. As a result, its operational efficiency is lower. 

The DC electricity is used to charge the batteries and also hits the inverter circuit, which converts the DC power to AC power. 

As a result, we may state that we produce clean AC power for the load. Because the load is always fed by the inverter portion, it must always be operational or on, therefore people named it “Online UPS”.

  • Pros of Online UPS
  1. The ability to manage huge capacity loads is one of the biggest advantages of online ups. 
  1. Produces clean sine wave electricity, which lowers the cost of electricity. It can be anything from (1KVA to 8000 KVA). 
  1. Increases the amount of time that the battery can be used as a backup power source.
  • Cons of Online UPS

Because these are large load capacity UPS, their size is likewise larger than offline UPS. Expensive when compared to an offline UPS.

What are Offline UPS?

The term “offline” refers to a situation in which converter operations begin after the mainline has been turned off or is unavailable.

When the mainline is unavailable, the offline system kicks in. Take, for example, the inverter system in our home. When there is no power from the mains, a UPS converts battery energy into electrical energy, allowing household equipment to function properly.

After a power outage, an offline UPS kicks in 7–8 seconds later. When they switch, they even make a buzzer sound.

The rectifier circuit of an offline UPS converts AC to DC, which is then fed to the batteries to charge them. When the power goes off, the batteries discharge into an inverter circuit, which provides the required power to the load.

  • Pros of Offline UPS
  1. The major advantage of offline UPS is its modest size and portability. The majority of the time, it’s used in the home. 
  1. These are quite inexpensive and easy to acquire.
  • Cons of Offline UPS
  1. Power backup is limited, and it can’t manage a heavy load.
  1. It can only provide backup for 5 to 15 minutes at a time.

Main Differences Between Online UPS AND Offline UPS

  1. To get the AC power supply directly in Online UPS it uses the AC-DC inverter. In offline UPS, the AC-DC power is used only in case of power failure.
  1. The output in the case of online UPS is stable continually and nearly fixed to a specific frequency. While the output in the case of offline UPS is not stable and varies very often.
  1. Online UPS uses the battery almost all the time when the electronic device is in on mode. Offline UPS uses the battery rarely, it only uses the battery when there is a power failure like a power cut.
  1. Since the Online UPS has to work throughout the time the operating temperatures are always high. But the offline UPS works only when there is a power failure and the operating temperature is not high.
  1. The reliability in the event of online UPS is low as it provides unreliable services. In the event of offline UPS, the reliability is high as it provides reliable services only.


UPS’s objective is to offer a continuous power supply as well as power backup.

Both UPSs have their own set of features. The need for any type of UPS is determined by the nature of the load. For example, if your primary objective is to power your computer, you can opt for an offline UPS, which has a lower load and can easily provide a power backup of 10–15 minutes.

If you need more than one computer and wish to run numerous PCs, an online UPS is the way to go. An online UPS has the advantage of delivering pure sine wave power and being able to handle a huge quantity of load.

The decision between the two is based on your needs and the load. Online UPS is suggested for heavy loads, whereas offline UPS is appropriate for lesser weights.


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