A UPS sits under a desk or in a closet for years, and for most of that time it should be silent. Two things break the silence: a cooling fan, which some units run all the time, and the alarm that beeps when the power fails. Makers cover the first with a noise figure on the spec sheet and the second in the manual, and this guide uses both.
We compared 15 current units from APC, Eaton, Tripp Lite and CyberPower that publish a maker noise figure. Their figures run from 35 dBA for APC's smallest Back-UPS to 51 dB at 1 meter for online towers from Eaton and Tripp Lite.
Four makers, four ways to state noise
APC lists an "Acoustic level" in dBA, with no distance, load or operating mode. Eaton gives dB at 1 meter on its product pages, and sometimes dBA in its manuals and spec sheets for the same unit. Tripp Lite, now sold through Eaton, measures from the front: "Less than 36 dB, front side 1m" for the SMART1500LCDT. CyberPower measures at 1 meter for some units and 1.5 meters for others, and gives its online units a range from no load to full load.
Those conventions do not convert into each other, so a lower number from one maker is not proof of a quieter unit than another maker's. We rank within each convention, and when a pick crosses them, as the APC BE600M1 and Tripp Lite SMART1500LCDT do, we say so.
Load changes the number
CyberPower's online units show how much load matters. The OL1K5RTHD is rated at 17.3 dBA at no load and 47.6 dBA at full load, both at 1 meter. Tripp Lite's SmartPro SLT manual says why: its fan "runs continuously" and speeds up "when the UPS is in battery backup mode, charge mode, carrying a heavy electrical load or an over-temperature condition." A UPS sized well above your actual load is likely to run quieter than one working near its limit.
Online units are the loud ones
Online double conversion units run their power through the inverter all the time, and in this survey they carry the highest figures: 51 dB at 1 meter for Eaton's 9SX1500 and Tripp Lite's SU1000XLCD. Eaton's own documents disagree slightly on the 9SX, whose product page says "51 dB at 1m" while its spec sheet says "< 50 dBA at 1 meter typical." For a desk or bedroom, a line-interactive unit is the quieter class.
Sine wave or stepped
On battery, the SMART1500LCDT produces what Tripp Lite calls "quasi-sine (PWM)" and the BE600M1 what APC calls a "stepped approximation to a sinewave." Both are common choices for modems, routers and small electronics. For a desktop PC, workstation or NAS, a sine wave unit such as the Eaton 5SC1500 or APC SMC1000C is the safer choice.
Silencing the beeper
For most people, the loudest thing a UPS ever does is beep during an outage. APC's Smart-UPS SMT manual says the unit "will mute all audible alarms" when its Audible Alarm setting is Off. Tripp Lite's SMART1500LCDT has a silent mode that "will deactivate the beeper completely," but it can only be turned on while the unit is on utility power, and Tripp Lite notes that the low battery alarm still sounds when the battery alarm is only temporarily muted. On the SmartPro SLT, continuous alarms warning you to shut down equipment "cannot be silenced." Some Tripp Lite units skip the outage beep entirely: the ECO850LCD and AVR750U pages say the "UPS remains silent in battery backup mode," sounding only for low battery, faults, overloads and battery replacement, though neither publishes a noise figure. Read your model's manual before an outage, not during one.
Who publishes nothing
CyberPower publishes no noise figure for any current desktop or tower unit we found, including the CP1500PFCLCD, only a feature called "Ultra Quiet Design." Several APC lines, such as the BVN and BVK Back-UPS models, have no acoustic row. Tripp Lite's OmniVS, ECO and AVR units list none either. That does not make them loud, but without a figure they cannot be ranked here.
We did not measure any of these units. Every figure is the maker's own, quoted as published, with the distance, load or mode it comes with, or a note when the maker gives none.
