Best UPS for a NAS: pure sine, USB/NUT and small-rack picks

Already own one of these UPS units and losing runtime? Our APC and CyberPower replacement-battery guide maps exact cartridges, explains the CyberPower serial-prefix split and walks through the swap, charge and self-test.

Want a local UPS dashboard or direct SNMP monitoring? Our APC vs CyberPower network-card guide maps compatible slots and explains when USB/NUT already gives you everything you need.

The short answer: buy capacity and a shutdown path

Need more organised outlets after the UPS? Our homelab rack PDU guide covers unfiltered distribution, load displays and local network switching, with the UPS and circuit limits kept in charge.

For a NAS with local USB shutdown, start with the CyberPower CP1500PFCLCD, current a revision: sine-wave output, six battery-backed outlets and USB HID management. Prefer APC? Choose BR1500MS2 for the pure-sine alternative, or SMC1500C when you need eight battery-backed outlets; the selected SMC offer includes USB storage.

The existing APC BR1000MS remains the modest single-box pick, and Eaton 5SC1000/1500 remain the eight-outlet options. BX1500M is the stepped-sine contrast: choose it when that waveform fits your equipment. These are alternatives—pick one UPS for the load and shutdown plan you need.

Specifications and shutdown guidance come from the makers, NUT and NAS documentation.

APC vs CyberPower vs Eaton: the buying table

UPS	VA / W rating	Battery waveform / topology	Battery + surge / surge-only outlets	Management and NUT evidence	Replaceable battery
APC BR1000MS	1,000 VA / 600 W	Sine wave / line-interactive	6 / 4 NEMA 5-15R	USB data; BR1000MS report uses usbhid-ups; reported shutdown sequence untested	User-replaceable; APCRBC160
CyberPower CP1500PFCLCD, current a revision	1,500 VA / 1,000 W	Sine wave / line-interactive	6 / 6 NEMA 5-15R	HID USB data; older model DDL plus CP1500PFCLCDa handling in NUT driver source	Yes; match cartridge to serial number
Eaton 5SC1000	1,000 VA / 700 W	Pure sine wave / line-interactive	8 / 0 NEMA 5-15R	HID USB and RS-232 via RJ45; 5SC USB family listed with usbhid-ups	User-replaceable, front access
Eaton 5SC1500	1,440 VA / 1,080 W	Pure sine wave / line-interactive	8 / 0 NEMA 5-15R	HID USB and RS-232 via RJ45; 5SC USB family listed with usbhid-ups	User-replaceable, front access
APC BR1500MS2	1,500 VA / 900 W	Sine wave / line-interactive	6 / 4 NEMA 5-15R	USB data; Back-UPS Pro USB family uses usbhid-ups	User-replaceable; APCRBC163
APC BX1500M	1,500 VA / 900 W	Stepped approximation to a sinewave / line-interactive	5 / 5 NEMA 5-15R	USB data; APC USB family evidence	User-replaceable; APCRBC124
APC SMC1500C + USB storage bundle	1,440 VA / 900 W	Sine wave / line-interactive	8 / 0 NEMA 5-15R	USB and serial; SmartConnect cloud port separate	User-replaceable; RBC6

The APC datasheet, CyberPower datasheet and Eaton brochure supply the original four models’ hardware ratings. Eaton’s 5SC1000 and 5SC1500 pages establish line-interactive topology. For the US 5SC1500, use the electrical-output specification of 1,440 VA, despite the page’s 1,500 VA headline.

The new APC rows use the maker’s BR1500MS2, BX1500M and SMC1500C sheets. Compare W/VA, waveform, outlet count and USB management separately, then choose runtime for your measured load.

Best UPS for a NAS: pure sine plus a real USB data port

A NAS UPS has two jobs: keep the disks powered through the interruption, then tell the NAS when it is time to stop. Buy the shutdown path as well as the battery. A front-panel USB charging socket cannot deliver that message.

For a new NAS or server purchase, start with the CyberPower CP1500PFCLCD’s current a revision. It combines sine-wave output, six battery-backed outlets and USB HID management. CyberPower explicitly lists active-PFC power-supply compatibility. The APC BR1500MS2 is the pure-sine APC alternative, also with six battery-backed outlets; the SMC1500C gives you eight.

The BX1500M is the contrast pick, with what APC calls a “stepped approximation to a sinewave.” Choose it only when that waveform meets your equipment’s power-supply requirements. Sine-wave output is the simpler starting choice for a new active-PFC NAS/server build; the BX’s similar VA/W label does not make its output identical to the BR1500MS2’s.

That is different from topology. These APC models and the CyberPower are line-interactive units, not zero-transfer-time online UPSs. Waveform, transfer, runtime and USB communication are separate specifications. Our power-station-as-UPS guide shows why a larger portable battery needs the same questions answered.

Does it talk to my NAS?

The NUT hardware compatibility list is the driver starting point. The table distinguishes exact device reports from family records, because your NAS also ships its own software version.

UPS	NUT USB evidence	Buying role
CyberPower CP1500PFCLCD / current a revision	usbhid-ups; older exact-model dump plus current a-revision handling in the CyberPower driver	Starting NAS/rack pick; sine wave
APC BR1500MS2	Back-UPS Pro USB family: usbhid-ups; no exact MS2 entry found in the checked HCL	Pure-sine APC alternative
APC BX1500M	APC Back-UPS USB family: usbhid-ups; no exact BX1500M entry found in the checked HCL	Stepped-sine option for compatible equipment
APC SMC1500C	Smart-UPS USB family and older C1500 dump: usbhid-ups (family-level evidence)	Eight-outlet APC option
APC BR1000MS	Back-UPS RS 1000MS device record: usbhid-ups; submitted shutdown sequence was untested	Retained modest single-box pick
Eaton 5SC1000 / 5SC1500	5SC USB family: usbhid-ups, rather than individual shutdown records	Retained eight-outlet Eaton options
GOLDENMATE 600VA	No matching 600VA NUT entry found; the listed 1000VA models are different hardware	Leave off the automatic NAS-shutdown shortlist

The APC C1500 device report names Smart-UPS C 1500; use it alongside the Smart-UPS family entry when choosing the driver. For every pick, finish setup with an on-battery status check and a complete shutdown/recovery test in the NAS software you will use.

Which USB port—and which cable?

Use the UPS’s management connection and a matching data cable. On the BR1500MS2, the front USB-A/USB-C charging ports are separate from UPS communication. On the SMC1500C, SmartConnect Ethernet is cloud monitoring; local USB management is a separate connection. Its selected Amazon offer is a tower UPS bundled with 16 GB USB storage. The flash drive is a bundle extra, not the UPS data connection.

GOLDENMATE’s six-outlet 600VA maker page describes simulated-sine output and PC communication. The lithium battery is interesting, but choose one of the documented driver routes above for this NAS job until a matching 600VA NUT record is available. Do not substitute its five-outlet wall-mount sibling or a 1000VA driver report.

Set up USB shutdown in TrueNAS, Unraid or Synology

Start by plugging the NAS into a battery-backed outlet, then connect the management cable directly to the machine that will monitor the UPS. Keep that USB device available to the host instead of passing it into a VM that should shut down first.

TrueNAS: the 25.10 UPS service guide uses NUT. Open System → Services, edit UPS, select the driver and USB device that match the NUT record, then set the shutdown policy. Save the configuration and start the service. The NUT usbhid-ups manual explains the USB driver; a basic standalone NUT configuration uses driver = usbhid-ups and port = auto.

Unraid: open Settings → UPS Settings for its built-in UPS support. That service uses apcupsd, not NUT. The Unraid UPS guidance covers USB connection and shutdown thresholds. If you choose the NUT plugin instead, follow the NUT project’s Unraid setup: set Start APC UPS daemon → No, apply the change, then configure NUT. One service should own the USB UPS, not two competing daemons.

Synology DSM: open Control Panel → Hardware & Power → UPS, enable UPS support and select USB UPS. Choose the time before Standby Mode as described in Synology’s USB UPS instructions. Standby Mode stops services and unmounts volumes; build that step into the shutdown plan rather than expecting the NAS to run until the battery is flat.

Test the boring bit before the first outage

1. Confirm live status. With mains available, the NAS should report the UPS and battery state. Look for battery charge and mains/battery status in the NAS interface.
2. Choose shutdown reserve. Allow time for applications, VMs and storage to stop, plus a margin for an ageing battery. The UPS sizing guide gives you the worksheet.
3. Run a controlled power-loss test. Follow the UPS maker’s procedure, with a current backup and nonessential work first. Confirm that the NAS sees battery operation and completes its configured shutdown before power runs out.
4. Restore input and check recovery. Observe the UPS output, NAS restart behavior and storage status. If another machine supplies network UPS status, keep the network path powered until shutdown finishes.

Choosing the NAS too? Our UGREEN DXP2800 vs Synology DS225+ comparison separates media and backup roles. Give whichever you choose enough time to close its work cleanly.

Modest single-box load: APC

Choose the APC for the modest single-box case. Its six battery-backed outlets are enough for a single host and a deliberately small set of shutdown dependencies, provided their combined W and VA budgets fit.

For scale, the existing UPS-sizing worksheet chooses a 240 W host at 0.96 power factor. That is 250 VA; applying the worksheet’s chosen 25% growth allowance to that host alone gives 300 W / 312.5 VA. Those are illustrative inputs, not typical consumption figures. They fit the APC’s ratings, leaving runtime as the next decision.

Small-rack pick: CyberPower

For a host, switch and NAS, start with the CyberPower, provided six battery-backed outlets cover the equipment that must survive the outage. Its other six outlets are surge-only: they do not keep a switch or shutdown controller running on battery.

The sizing guide’s complete fictional rack adds a 30 W / 50 VA network load and 10 W / 20 VA controller to the host. Total demand is 280 W / 320 VA, or 350 W / 400 VA after the chosen growth allowance. All seven selected models clear that capacity worksheet. Choose between them using outlet requirements, runtime evidence, management support and physical fit rather than treating the largest VA label as necessary.

CyberPower’s manual recommends keeping load below 80% of rated capacity for optimal performance. For the current version, keep the design below 800 W and 1,200 VA. The illustrative rack clears both; use the model’s runtime information to plan minutes on battery.

Check the delivered revision carefully. Amazon’s model field identifies CP1500PFCLCDA, matching the vendor’s CP1500PFCLCDa specifications. Older CP1500PFCLCD records describe 900 W hardware. Do not apply the current 1,000 W limit or replacement-battery choice to an older unit by name alone.

When eight Eaton battery outlets matter

Buy the 5SC1000 when eight direct battery-backed outlets solve a real connection problem and 700 W / 1,000 VA covers your planned load. Buy the 5SC1500 when that outlet arrangement matters and you need the higher 1,080 W / 1,440 VA capacity. Both have USB HID data and a separate serial connection; the serial RJ45 connector is not an Ethernet management interface.

Choose the Eaton when eight battery-backed outlets solve the connection requirement. Count devices that genuinely need battery power and check their plug spacing.

Eaton documents front-access battery replacement. Keep access and ventilation clear when choosing a shelf; fitting the cabinet’s footprint is not enough if you cannot service the battery. Follow the exact replacement procedure and select the supported pack rather than assuming every battery that physically fits is suitable.

For a two-GPU inference box, measure the whole protected load

The CyberPower is the first capacity candidate, not an automatic match for two GPUs. A PSU output-capacity label and GPU telemetry do not give the protected equipment’s AC W/VA demand. Include the rest of the host and any switch or storage dependency needed for shutdown. The plug-in meter comparison helps choose the measurement tool.

For a buying example, choose an already-planned budget of 700 W / 800 VA. This is an arbitrary worksheet case, not a measured or typical two-GPU system. It fits the current CyberPower’s below-80% recommendation. The 5SC1500 also clears both nameplate limits and provides eight battery-backed outlets. The 5SC1000 would sit at its watt ceiling; choose a model with room for the actual design instead.

If the measured load and chosen reserve exceed the candidate’s limits, reduce the protected load or select a different UPS. Select runtime separately from output capacity.

Read the revision-specific NUT records

Use the management data connection, not the front charging ports. The APC BR1000MS NUT report identifies usbhid-ups and explicitly leaves its shutdown sequence untested. The CyberPower DDL covers an older 900 W unit; NUT’s CyberPower driver source separately names CP1500PFCLCDa handling. The compatibility list supplies 5SC-family USB evidence for Eaton, not an exact 5SC1000/1500 shutdown test.

During the shutdown test, follow the complete sequence: status reporting, the shutdown decision, host halt, UPS output behavior and restart. Keep required communication equipment powered until the host has finished.

Give the battery box proper support as well as suitable power. Our small rack and shelf guide separates tower-UPS shelving from four-post rack equipment, with depth, load and cable-space checks.

Buy enough time, not just enough watts

Use the sizing guide to define the protected load, runtime target and shutdown order. Check the exact model’s runtime information at that load, then validate the complete design under stated battery and charge conditions. Do not turn VA or battery watt-hours into guaranteed minutes.

Choose CyberPower for the pure-sine NAS/rack starting point, BR1500MS2 for the APC alternative, and SMC1500C or Eaton when eight battery outlets matter. Keep BR1000MS for the modest single box; choose BX1500M only for equipment that accepts stepped sine. The useful UPS fits the load and finishes the shutdown you planned.

Need longer networking runtime or a battery you can take with you? Our portable power station as a UPS guide compares transfer times, router runtime and the RIVER 3 Max’s USB shutdown route.

For a router and ONT that can use DC backup directly, our DC mini UPS guide walks through voltage range, polarity, plug fit and runtime estimates before you choose a pack.