Four brands, four ways of stating noise
None of these ratings compares cleanly across brands, because each maker states noise in a different way.
| Maker | How the figure is stated | Units in this guide |
|---|
| APC | "Acoustic level" in dBA; no distance, load or operating mode | BE600M1 35 dBA; BE425M 40 dBA; SMC1000C and SMT750C 41 dBA; BX1500M, BR1500MS2, SMT1500C and SMC1500C 45 dBA |
| Eaton | dB at 1 meter on product pages, sometimes dBA in manuals and spec sheets for the same unit | 5SC1500 under 40 dB; 9SX1500 51 dB, or under 50 dBA on the spec sheet |
| Tripp Lite, now sold through Eaton | Measured from the front at 1 meter | SMART1500LCDT under 36 dB; SMART1500SLT under 50 dBA; SU1000XLCD 51 dB |
| CyberPower | 1 meter for some units, 1.5 meters for others; a load range for online units | OL1K5RTHD 17.3 to 47.6 dBA at 1 m; OR1500PFCRT2U 48.7 dBA at 1.5 m |
These conventions do not convert into one another. A lower number from one maker is not proof of a quieter unit than another maker's, so the ranking stays within a convention, and where a pick crosses one, as the APC BE600M1 and Tripp Lite SMART1500LCDT do, the page says so.
Load drives the fan
CyberPower's online OL1K5RTHD shows it plainly. At no load it is rated 17.3 dBA, at full load 47.6 dBA, both at 1 meter, a spread of more than 30 decibels from one machine.
Tripp Lite's SmartPro SLT manual explains the mechanism. 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." Load is in that list, and so is charging after an outage, which means a UPS can stay loud for a while once the power comes back. Sizing a unit well above the actual load is likely to keep it quieter than one working near its limit. Portable power stations behave the same way, with fans that spin up under heavy load or fast charging, as the power station guide explains.
An online double conversion UPS runs its power through the inverter all the time. In this survey that class has the top figures: 51 dB at 1 meter for Eaton's 9SX1500 and Tripp Lite's SU1000XLCD.
Even Eaton's documents differ on the 9SX: the product page says "51 dB at 1m", while the spec sheet says "< 50 dBA at 1 meter typical."
Set those beside the line-interactive picks, under 40 dB at 1 meter for Eaton's 5SC and under 36 dB for Tripp Lite's SMART1500LCDT, and the class difference is clear. For a desk or bedroom, line-interactive is the quieter choice.
Do you need a pure sine wave UPS?
For a desktop PC, workstation or NAS, yes, a sine wave unit such as the Eaton 5SC1500 or APC SMC1000C is the safer choice.
On battery, the SMART1500LCDT puts out what Tripp Lite calls "quasi-sine (PWM)" and the BE600M1 what APC calls a "stepped approximation to a sinewave." Those are common choices for modems, routers and small electronics.
Anyone buying for a NAS will find the published noise figures of the boxes themselves compared in our NAS guide.
How do you stop a UPS beeping during a power outage?
Switch the alarm off in the settings, and do it before an outage. With its Audible Alarm setting at Off, an APC Smart-UPS SMT "will mute all audible alarms", according to the manual.
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. Tripp Lite also notes that if the battery alarm is only temporarily muted, the low battery alarm still sounds. Some alarms cannot be switched off at all. On the SmartPro SLT, continuous alarms warning you to shut down equipment "cannot be silenced."
A few Tripp Lite units skip the outage beep altogether. 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 the manual before the lights go out, not by flashlight.
Every current CyberPower desktop and tower UPS we found goes without a figure. The CP1500PFCLCD, for one, lists only a feature called "Ultra Quiet Design."
APC and Tripp Lite have gaps too: the BVN and BVK Back-UPS models have no acoustic row, and Tripp Lite's OmniVS, ECO and AVR units list none. That does not make them loud. Without a figure, though, they cannot be ranked here.
