Difference Between Online UPS and Offline UPS

Edited by Diffzy | Updated on: April 30, 2023


Difference Between Online UPS and Offline UPS

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It is often said that 'Uninterrupted Power Supply (UPS)' is as essential to the IT world as uninterrupted air is to humans. Some way or another, we must feed input power to our electronic gadgets for them to function. It is not always possible to plug electronic items into the AC adapter. Even if we connected to such inputs, we could not rely on them 100%. In this case, an attractive solution is available to solve the issue - Uninterrupted Power Supply (UPS). Yes, it can provide uninterrupted power for electronic devices. Hence its name.

Online UPS vs. Offline UPS

An online UPS system provides power to connected equipment by converting AC to DC, then back to AC. The inverter in an online UPS is always on, providing a continuous flow of power to connected equipment. Because the inverter is always on, an online UPS is more expensive to operate than an offline UPS. An offline UPS also converts AC to DC, but it uses a battery to provide power to connected equipment during a power outage. The battery recharges when utility power is restored, so it's ready for the next power outage. Offline UPS systems are less expensive because they don't require 24/7 operation as an online UPS does. They're designed for one-time use - after the battery fully charges, it should be replaced with a new one.

Difference Between Online UPS and Offline UPS in Tabular Form

Parameters of


Online UPS Offline UPS
Define The Online UPS is a type of UPS that supplies power to the AC load through the Rectifier and Inverter Combo in normal operation and uses an inverter to supply AC power during a power failure. The offline UPS is a type of UPS that directly supplies the power to the AC load from the AC mains in normal operation and uses an inverter to power the AC load from the DC battery.
Transfer time The transfer time in the case of Online UPS is zero as there is no switching between the inverter rectifier path and mains supply path The transfer time in case of Offline Ups possesses a transfer time of about 5ms.
Cost The cost of the online UPS is more The cost of the offline UPS is less
Efficiency The efficiency of the offline UPS is more The efficiency of the offline UPS is more
Inverter The inverter in online ups is ON all the time The inverter in offline UPS is on only when the power supply is unavailable.

What is Online UPS?

Online UPS systems provide backup power and protect equipment from power surges, voltage fluctuations, and outages. Unlike traditional UPS systems, online UPS systems do not require a break in the power supply to switch to battery power. This makes them ideal for mission-critical applications where downtime is not an option. Online UPS systems are also more efficient than traditional UPS systems, as they convert AC to DC power more efficiently. As a result, the magnitude plot produced by the FFT will not show any amplitude difference between these two signals. In contrast, the DFT will create both graphs of differing magnitudes.

Operating Temperature of Online UPS

Regarding UPS systems, there are two main types of units available today. These are offline UPS and online UPS systems. So, what's the difference between these two types of UPS systems? And more importantly, which one is right for your needs? The main distinction between the two UPS types lies in how they operate. Offline or stand-alone UPS systems function by maintaining power at all times to an entire house or building with a single inverter. Conversely, an online system provides power when electricity from the grid is lost and draws energy from a battery when electricity from the grid is present. In addition, with this type of system, power can be provided back to the grid if needed and desired during outages to maintain continuity for residences and businesses without interruption.

Parts Used in Online UPS

Fast Fourier Transform (FFT) and Discrete Fourier Transform (DFT) are two algorithms used for signal processing. They are both used to convert a signal from one domain to another but differ in their applications and implementation. FFT is used for digital signal processing, while DFT is used for analyzing analog signals. FFT can be implemented in hardware or software, while DFT can only be implemented in software. FFT is faster than DFT, but DFT is more accurate. Many people think that DFT should replace FFT because it is more accurate, but this isn't true. For example, with an impulse signal where the frequency content of each part is related to each other by whole numbers as described below:

f1=2f2+1; f2=3f1+2; f3=4f2+3

The inverse transform would occur as follows: The two types of transforms - Discrete Fourier Transform (DFT) and Discrete Cosine Transform (DCT) - calculate the same. However, DCT does not require double-precision calculations, so it executes faster than FFT.

Cost of Online UPS

An uninterruptible power supply (UPS) is an essential component when it comes to powering critical equipment. But what kind of UPS is right for your needs? One option is a transformer-based UPS, which provides clean and consistent power. Another option is a switch-based UPS, which can be more cost-effective.

Reliability of Online UPS

A UPS, or uninterruptible power supply, is a device that provides backup power to devices in the event of a power outage. Online UPS systems are becoming increasingly popular because they provide clean and uninterrupted power. However, before making a purchase, you should be aware of some critical differences between online and offline UPS systems. Offline UPS systems will provide power for as long as the battery lasts; when the battery dies out, so makes your connection to the grid. In contrast, online UPS batteries will maintain energy from the grid during an outage and switch over seamlessly once service has been restored. You'll also notice that these two types of UPS have different surge protection capabilities. The former protects against surges only at the input level, while higher-end models protect against both input and output levels (i.e., plugs).

What is Offline UPS?

Offline UPS, also known as standby UPS, is the most basic type of UPS. It provides power to devices connected to it only during an outage. When power is lost, an offline UPS will switch to battery power and give a short-term backup until power is restored. The main advantage of an offline UPS is its low cost. However, since it only provides power during an outage, it may not be suitable for devices that require continuous power, such as servers or medical equipment. A better option would be an online UPS, which stores enough energy in its batteries to keep your device running through an entire blackout. Most of these systems are designed with enough capacity to run your computer system and other critical gear at full load for 20 minutes. Most come with software that adjusts power output as needed to accommodate any fluctuations in incoming voltage. And because they can draw electricity from the grid or their battery banks, they won't go down if one fails.

In addition, both types use flywheels to store energy between periods where electricity is available from either source - but this process has little effect on performance given the average downtime associated with each event.

Operating Temperature of Offline UPS

The operating temperature of an offline UPS is one of the most important factors to consider when choosing a UPS for your business. An offline UPS can be used in various environments, but it must be able to withstand the temperature extremes of its intended location. If an offline UPS is exposed to high temperatures, choosing a model with a high maximum operating temperature is essential. Conversely, if low temperatures are a concern, select a UPS with a low minimum operating temperature. To maintain optimum performance, use the following guidelines:

One thing you should remember when looking at battery-based offline units is that they have limited capacity at extreme temperatures. For instance, a UPS designed for indoor use may only have about two hours of battery life at -40°F (-40°C).

Parts Used in Offline UPS

When it comes to choosing a UPS for your business, you have two main types to choose from: offline and online. But what's the difference between these two types of UPS systems? And which one is suitable for your business needs? Let's take a closer look at the critical differences between FFT and DFT to help you make the best decision for your business. A standard-size UPS system consists of three components:

  • A battery (a source of stored energy).
  • A rectifier (which converts AC power into DC power).
  • A control system (which regulates the output voltage).

One significant difference between offline and online UPS systems is that with an offline unit, the battery provides backup power in case there are any issues with incoming administration or if there are sudden spikes in demand that would otherwise cause outages. With an online unit, however, its function is limited to regulating incoming electricity so that equipment stays operational during short-term outages caused by brief interruptions in input power.

Cost of Offline UPS

There are two main types of UPS systems: offline and online. Offline UPS systems are less expensive than online UPS systems but offer less protection. With an offline UPS, power is supplied to the UPS only during a power outage. This means that your equipment will not be protected if there is a power surge. Online UPS systems, on the other hand, provide constant power to your equipment, even during a power outage. This makes them more expensive, but they offer better protection for your equipment. The exception is if you have a battery backup system installed in your building, which can keep everything running as long as there's enough power stored in the battery bank.

Reliability of Offline UPS

A UPS, or uninterruptible power supply, is a device that provides backup power to devices that require a continuous supply of electricity. There are two main types of UPS systems: offline and online. Offline UPS systems are less expensive and more reliable than online UPS systems. These units use their batteries to keep the system running while they use their inverters to provide power during an outage. Online UPS systems have a battery that lasts only 5-10 minutes during an outage before switching from battery backup to utility power. The primary benefit of these units is that they don't need any manual intervention to switch over between sources; it does this automatically with most models equipped with special software that can detect outages.

Main Differences Between Online UPS and Offline UPS in Points

  • Online UPS systems have a rectifier that converts AC to DC, while offline UPS systems do not.
  • Online UPS systems have a battery backup, while offline UPS systems do not.
  • Online UPS systems are more expensive than offline UPS systems.
  • Online UPS systems are more reliable than offline UPS systems.
  • Online UPS systems provide better protection against power surges than offline UPS systems.
  • Online UPS systems can be used with computers, while offline UPS systems cannot.
  • Online UPS systems are more challenging to install than offline UPS systems.
  • Offline UPS systems require less maintenance than online UPS systems.


In the end, both the FFT and DFT are potent tools that can be used to analyze data. The critical difference between the two is that the FFT is much faster than the DFT. So, the FFT is the way to go if you need to quickly analyze a large amount of data. However, if accuracy is your main concern, you should use the DFT. You may have to take more time on this one, but in the end, it'll pay off with higher-quality data. As always, there are trade-offs!

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"Difference Between Online UPS and Offline UPS." Diffzy.com, 2023. Mon. 05 Jun. 2023. <https://www.diffzy.com/article/difference-between-online-ups-and-offline-ups-861>.

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