Line Interactive vs Online UPS: Which system is right for you?

In one of our Newbie’s Nook segments, we briefly touched on the differences between the three types of single-phase UPSs: standbyline interactive, and online. That post focused on basics of each device handling a power issue; this post is focused, specifically, on the differences between line interactive and online UPSs in order to find the best fit for your power needs.

While both UPSs provide full protection from major power problems, such as surges, spikes, sags, blackouts and brownouts, they differ in a few significant areas. Simply put, an on-line UPS offers a higher level of protection than a line interactive at a higher cost. More specific areas where the two types differ include sine wave output, voltage regulation, and double-conversion inversion.

Sine Wave Output

Without boring you with too much detail, there are three types of wave currents: squaresimulated sine, and true sine. While each wave alternates between positive and negative to create a current, the three are vastly different.

Square waves are typically produced by lower end equipment and, despite cost benefits, may put strain on the connected equipment that can lead to operation problems.

The next step up is a compromise between power quality and cost with a simulated sine wave. While this wave is still less than ideal, the shape of the wave more closely resembles a pure sine wave and therefore, offers a better quality current. With the exception of the EnterprisePlus LCD, all of Minuteman’s line interactive UPSs employ this simulated sine wave to deliver utility power to equipment.


Finally, the best quality wave is the true or pure sine wave.

This is the ideal wave for both equipment performance and longevity. Power transitions smoothly between positive and negative to create the perfect wave and ensure the best quality power is delivered to equipment. While this wave produced great performance and is safe for sensitive equipment, it does come at a higher cost. Minuteman’s online UPSs all come with true sine wave output, as well as one line interactive unit, the EnterprisePlus LCD, which simulates a true sine wave.

Therefore, with the exception of the EnterprisePlus LCD, Minuteman’s line interactive units offer a simulated sine wave while the online UPSs have true sine wave output across all units.

Voltage Regulation

A line interactive UPS has two options when it comes to dealing with power, switch to battery power or buck/bump the power level to normal with an automatic voltage regulator (AVR).  As discussed in the Newbie’s Nook post: An AVR acts as a sort of gatekeeper and each unit has a range that covers slightly above and slightly below normal which is 110V. For instance, a range can be between 100v and 120v. So here are the options for the current: 1.) If the current coming from the wall is normal then it goes right through. 2.) If the current is abnormal but still within a certain range, the voltage regulator will either boost the current up to normal or bring it down to normal. 3.) However, if the current is abnormal and outside of the range then the UPS will switch to battery power just like the standby UPS.

AVR becomes very beneficial in areas with unreliable power because power can run though the UPS with voltage regulation pretty much indefinitely, unlike a battery where the power only lasts a certain amount of time.

Double-Conversion Inversion

Instead of employing a battery to prevent downtime, on-line UPSs only have one option to protect against power problems and that’s conversion. As complicated as ‘double-conversion inversion’ sounds, it’s a relatively simple concept. Firstly, an AC current is one that can run long distance but is not as high quality as DC power. Conversely, DC power is very high quality, but only for short distances, like the distance through a UPS. Thus, every current enters an online UPS as AC then is converted into DC, whether it is normal or not, and exits the unit as AC again. Essentially, an online UPS cleans up any current, ensuring the purest most high-quality current is entering the equipment attached to it.

How to Decide

While an online UPS is the top of the line protection available, it can be costly. These units are best suited for sensitive mission-critical equipment that handles very sizable amounts of power. Many people are looking for great protection that won’t hurt the budget too much, which is where the line interactive units come into play. Line interactive UPSs are a great balance between protection and quality. Minuteman’s line interactive UPSs range from 500VA to 3000VA to ensure the right fit for every system.

Minuteman’s on-line Endeavor Series offers units with true sine wave output and AC-DC-AC conversion ranging from 1-10kVA, making it ideal for sensitive, high-powered equipment. Minuteman’s line interactive UPSs have simulated sine waves with voltage regulation, making them a great compromise between cost and quality.

With its simulated true sine wave output, voltage regulation and versatility the EnterprisePlus LCD is a perfect bridge between the online and line interactive units. This UPS has factors typically associated with both the online and line interactive while also having independent battery bypass. Independent battery bypass ensures that after normal power is restored, the unit will move from battery power or voltage regulation back to utility power automatically.

Check out Minuteman’s online and line interactive series to choose the right level of UPS for your needs.



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