Difference between Online UPS and Offline UPS - A Buyer's Guide

Uninterruptible Power Supply (UPS) is a device that provides power backup for a while to operate electrical equipment like computers, fans, laptops, lights, televisions, etc. when there is a power cut, power failure, power fluctuation, or power surge. It provides instantaneous protection from such interruptions by supply power instantaneously. UPS are classified into two types including online UPS and offline UPS. This write-up discusses the difference between online and offline ups.

Offline UPS

In offline UPS, the role of an inverter is eliminated during normal operations, with the load being directly fed from the raw mains. The power storage modules like inverters, chargers and batteries are offline. The battery and charger remain connected to the mains so that the battery is fully charged. If the mains fluctuate or fail, the device directly switches to the inverter’s output to provide continuous and uninterrupted power supply.

Online UPS

Online UPS is a little bit different from offline UPS. In this case, during normal operations the system draws its power via charging and power conditioning modules, instead of the load being directly connected to the mains. The power received here is conditional power. In an online UPS, the power to be stored in a battery is first converted to DC, and then converted back to AC to operate household appliances. Therefore, online UPS is also known as “double conversion” UPS.

That is the difference between online and offline UPS. Now, let us discuss the advantages of online and offline UPS individually.

Advantages of online UPS

1. Load and main supply’s separately present.
2. Better regulation of voltage.
3. The load voltage quality is balanced, and free from fluctuations. This is because the inverter is always on.
4. The transfer time is practically zero because the inverter is always on; and therefore, there is no disturbance in the current when the mains fail.
5. Applications using online UPS are medical equipment, intensive care units, induction motor drives, etc.

Advantages of offline UPS

1. The efficiency of this system is high. This is because the charger is not constantly on.
2. These are affordably priced.
3. Internal controller is simpler.
4. The power handling capacity of the charger is greatly decreased.
5. Applications using offline UPS include emergency power supplies, printers, computers, EPABX, scanners, etc.

Often households opt for offline UPS systems than their online counterparts because of the higher energy efficiency and economical nature of the former. However, households that use highly critical loads should opt for the latter so that sensitive electrical appliances and data are protected.

Courtesy of Glowship Solar Power