What Are the Types of Uninterruptible Power Supplies?

What to know about the different types of UPS

Uninterruptible Power Supplies/Sources (UPS) are backup electrical energy sources designed to kick-in when main power fails. This can include voltage interruptions, spikes, surges—pretty much any instance where the UPS detects a significant enough reduction. Sizes and output can vary from small units meant to power a single computer to large units used to power entire buildings.

What Are Uninterruptible Power Supplies Used For?

Most UPS are meant to turn on almost instantly the moment a power disruption is detected, which provides an uninterrupted stream of electrical power to the systems they’re connected to. The amount of time a UPS can operate depends on the model, lasting anywhere from a few minutes, to several hours, to always-on. This gives users the time needed to either safely shut down their hardware, or connect to another power source. In the case of an always-on UPS, they continually protect critical equipment.

UPS are most commonly used to protect data communication systems or data centers, but are also available for small office or personal use. They can also be used to keep other important electronic devices powered during outages and surges, like cordless phones and security systems.


Offline/Standby UPS are the simplest type of UPS and function as battery backups. These models are designed to detect changes in voltage above and below specific points, switch to internal batteries, then convert that energy to AC power. The process can take up to 25 milliseconds, depending on the unit. AC power is then used to keep connected devices running. Offline/Standby UPS provide the smallest window of power backup, typically offering five to up to 20 minutes..

Examples of Standby UPS use include consumer electronics, security systems, and point-of-sale systems for retail stores.

APC 425VA Standby UPS


Line Interactive

Line Interactive UPS detect voltage fluctuations and act as a backup power source during blackouts and surges, just like Standby models. What sets a Line Interactive UPS apart is they use an internal autotransformer to detect and adjust for small changes in voltage without needing to switch to internal batteries. This allows Line Interactive UPS to protect connected devices from small voltage changes and brownouts without affecting its ability to act as a separate power source. Line Interactive UPS typically provide a slightly larger window of power backup—up to half an hour—but can last for several hours with capacity expansion.

Examples of Line Interactive UPS include the same kinds of devices used with Standby UPS, as well as networking equipment, mid-range servers, and home theaters.

Line Interactive UPS from Tripp Lite

Tripp Lite


Online/Double-Conversion UPS are the most advanced types of UPS and provide a constant stream of power. They convert AC power to battery power, then back to AC, which eliminates power transfer time since the units never need to switch power modes. The constant stream of power keeps internal batteries charged, which will activate in the event of power loss. The internal batteries will start to recharge automatically once external power is restored and the UPS starts cycling from AC to battery to AC power again. Online/Double-Conversion UPS are used for critical electronic equipment.

Examples of use include data centers, IT equipment, telecom systems, and high-end server banks.

BBP 1 kVA / 900 Watt Power Conditioner

Battery Backup Power, Inc

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