The 9 Best Rack Mount Battery Backups
Updated by · How we research
1U or 2U, line-interactive or online: nine rack UPS units compared on watts, sine wave, depth, runtime and monitoring. The CyberPower CP1500PFCRM2U ranks first. When users buy our independently chosen editorial recommendations, we may earn commissions to help fund the Wiki.
Watts, not volt-amperes, are what you size a UPS by. A rackmount UPS bolts into a standard 19-inch rack and keeps servers, storage and switches in home labs, small offices and network closets running through brief outages, then shuts them down safely. Modern active-PFC power supplies need a pure sine wave on battery.
At a Glance
Editor's Notes
October 16, 2026, by Ezvid Wiki Admin:
Most readers put a rack UPS in a shallow home or office rack, run gear with modern power supplies and need a few minutes to shut down cleanly. The CyberPower CP1500PFCRM2U suits that job, so it takes the top spot. Much of the early-2021 list had drifted. The CyberPower PR3000 is unavailable, the Vertiv Liebert GXT4 is no longer offered, and the Eaton 5P1500RC was down to a single unit at a steep price. The Tripp Lite SU1500 N listing now sells a different online model. We also dropped the Vertiv Liebert PSI5-5000, which needs a 208-volt circuit most readers don't have, and the Tripp Lite 500VA, because of mixed reliability reports. The old APC Smart-UPS SMT entry gives way to the APC Smart-UPS SMC1500-2UC, which costs about the same and does more.
We also fixed some unit errors in the old text, which mixed up volt-amperes, kilovolt-amperes and watts. Watts are what you size a UPS by, and every entry now gives both figures.
The Tripp Lite SMART1500LCD is the budget answer, with one caveat about its waveform that the guide explains.
The APC Smart-UPS SRT2200RMXLA and the lithium APC Smart-UPS SCL500RM1UC stay. Everything else is new, including the CyberPower OL1500RTXL2U, a lower-cost online unit, and two bigger CyberPower models for heavier loads.
One honest limit: we found only one independent review in this category, ServeTheHome's look at the CP1500PFCRM2U, and several maker spec pages wouldn't load for us. Most figures here come from makers' listings and spec pages, and we say so where it matters.
January 07, 2021:
We largely stuck to our guns in this latest update, believing that our previous choices are still currently the best rack-mountable UPS systems available to buy, although we did add a couple of affordable options to balance our list. While neither of these additions provides the same comprehensive remote management, connectivity options, and power as some of the more expensive, 2-unit models ranked here, they give you peace of mind and protection when running sensitive electrical equipment.
First is the Tripp Lite 500VA, which, while it won't see your system through a lengthy power outage, will certainly regulate your supply during brownouts and give you enough time to safely shut down your equipment and save any data, if necessary. Secondly, we added the APC Smart UPS SCL500R, which has higher-performing lithium-ion batteries and a sequencer to safely power your system on and off, while it also keeps temperatures in check.
March 20, 2019:
Rack-mountable battery backups take the power of a traditional uninterruptible power supply and put it in a convenient form factor. They're mostly intended for commercial use in media closets and network setups, and if you're in the market for one, you've probably got at least a little professional IT experience. So, we consulted with a couple online resources to see which brands and models are preferred by industry pros. Notably, Eaton apparently makes highly reliable units, and although their brand doesn't reach quite as far in the consumer market, they receive considerable praise from those in the know. For a very well-known option, it's hard to go wrong with anything by APC, and here we've highlighted their newest and most reliable line-interactive as well as on-line versions. CyberPower is another company that's a bit obscure, but makes a handful of high-quality and reasonably priced models. Similarly, Tripp Lite makes some affordable options, and the one listed gets good marks from technicians, and is relatively full-featured. Finally, Vertiv is a renowned power-distribution manufacturer, and particularly their Liebert PSI-5 is among the highest-performing models, though it is considerably expensive.
Special Honors
Network UPS Tools Network UPS Tools, or NUT, is free, open-source software that reads a UPS over USB, serial or the network and tells servers, storage boxes and other computers to shut down before the battery runs out. One UPS can signal several machines. Its hardware compatibility list shows which models and drivers are supported, which is worth a look before buying a unit for Linux or BSD systems. networkupstools.org
Size It By Watts, Then Check Runtime
Add up the power draw of everything you'll plug in, using the nameplate or a plug-in meter, and leave some headroom.
Every UPS carries two ratings: volt-amperes (VA), the big number in the model name, and watts, the real power it can deliver. You must stay under both, and watts is usually the one that runs out first (Wikipedia: Volt-ampere). A 1,500 VA unit may deliver 900 watts or 1,000 watts depending on the maker. Add up the power draw of everything you'll plug in, using the nameplate or a plug-in meter, and leave some headroom.
Then look at runtime at your load, not at the maximum. Rack units carry small batteries. CyberPower estimates its CP1500PFCRM2U runs about 3.1 minutes at full load and 10.2 minutes at half load, and ServeTheHome describes the batteries as sized for a clean shutdown, not for riding out a long outage (ServeTheHome). Runtime grows quickly as the load shrinks, so a lightly loaded closet of networking gear can run much longer. Most UPS systems are built for 5 to 15 minutes of backup (Wikipedia: Uninterruptible power supply). If you need more, buy a bigger unit or one that accepts external battery modules.
Check the plug, too. Units of about 2,000 VA and up often use a NEMA 5-20 plug, which fits only a 20-amp receptacle with a T-shaped slot, and 208-volt models need a dedicated circuit an electrician would install.
Line-Interactive, Online And The Sine Wave Question
Most affordable rack UPS models are line-interactive. They pass utility power through, correct sags and surges with a transformer without touching the battery, and switch to the inverter when the power fails. Online double-conversion units run the load from the inverter all the time, so there's no transfer gap and the equipment is isolated from the utility line. They cost more, waste more energy as heat and keep their fans running, which makes them noisy in a home office (Wikipedia: Uninterruptible power supply).
Waveform matters as much as topology. Many lower-cost units produce a stepped, simulated sine wave on battery. CyberPower itself pitches its simulated-sine models for equipment without active power factor correction (PFC) and its PFC Sinewave models for active-PFC power supplies. Most modern server, desktop and gaming power supplies use active PFC, and some may shut down when fed a stepped wave. If you're protecting computers or servers, choose a pure sine wave unit. Simulated sine is fine for modems, routers, switches and other small gear with simple adapters.
Fitting The Rack, Batteries And Shutdown Software
Rack gear is measured in units: 1U is 1.75 inches tall and 2U is 3.5 inches, and a standard rack is 19 inches wide with about 17.75 inches between the posts (Wikipedia: 19-inch rack). Depth is the number people miss. Short-depth units of about 9 to 11 inches fit shallow wall cabinets, while big units run 15 to 23 inches and need a four-post rack. A UPS is usually the heaviest thing in a rack, so mount it at the bottom on rails or a shelf rather than hanging it from the front ears alone.
Sealed lead-acid batteries wear out, typically in three to five years, and most units here let you swap them yourself. APC rates the lithium-ion battery in its SCL500RM1UC for about 10 years (APC). Recycle old batteries instead of throwing them away.
A UPS only protects your data if the computer knows when to shut down. Every unit here has a USB port for the maker's software, and network cards or APC's SmartConnect cloud service add remote alerts. For Linux and many storage boxes, the free Network UPS Tools project supports a long list of models. We checked each brand in the U.S. Consumer Product Safety Commission's database and found no recent recalls of these UPS lines (CPSC).
How we researched this
We compared 20 rack mount UPS models and accessories and screened 10 in depth. We read makers' spec pages where they loaded (APC's did; several CyberPower and Eaton pages did not, so some figures come from the makers' listings), one independent review from ServeTheHome, and patterns in owner feedback, and we checked every brand for recalls with the U.S. Consumer Product Safety Commission. We found no independent lab tests of rack mount UPS units.
Frequently asked questions
What is a rack mount UPS?
It's an uninterruptible power supply, or battery backup, shaped to bolt into a standard 19-inch equipment rack. Most are 1U (1.75 inches) or 2U (3.5 inches) tall. It keeps servers and network gear running through short outages and gives them time to shut down.
What size rack mount UPS do I need?
Add up the watts your equipment draws, then pick a unit whose watt rating, not just its VA rating, leaves some headroom. Then check the maker's runtime at that load, and measure your rack's depth before you buy.
How long will a rack mount battery backup run?
Usually minutes, not hours. CyberPower estimates about 3 minutes at full load and 10 at half load for its CP1500PFCRM2U. Light loads run much longer. For more time, choose a model that accepts external battery packs.
Do I need a pure sine wave UPS?
For computers and servers with active-PFC power supplies, yes, since some of them misbehave on a stepped, simulated sine wave. Routers, switches and modems with simple adapters are fine on either.
What is the difference between line-interactive and online UPS?
A line-interactive UPS passes utility power through and switches to battery in a few milliseconds when the power fails. An online UPS runs the load from its inverter all the time, so there's no switch-over, but it costs more and its fans run constantly.
How often should UPS batteries be replaced?
Sealed lead-acid batteries typically last three to five years. APC rates the lithium-ion battery in its SCL500RM1UC for about 10 years. Most rack units let you replace the battery yourself.
