UPS Runtime Estimator for NAS: How Long Will Your NAS Stay On?

This estimator shows how long a UPS keeps your NAS running in a power cut. It reads the runtime from the maker's own published runtime curve for that UPS at your load, with a new, fully charged battery, and checks it against the time your NAS needs to shut down safely.

Runtime falls much faster than load rises, so a battery capacity formula is not used. Pick your NAS (or enter its watts), add anything else plugged into the UPS, pick the UPS, and enter how long your NAS takes to shut down.

It covers 5 UPS models sold in Australia whose makers publish a runtime curve. For another model, use its maker's runtime chart.

1. What is on the UPS

Your NAS

NAS watts

Filled from the maker's busy figure when you pick a NAS. A plug-in power meter gives your own.

Other devices on the UPS (total watts)

Router, modem, switch: the watts on each label or data sheet, or a power meter reading.

UPS model

2. How long the NAS needs

Minutes on battery before shutdown starts

The wait you set in your NAS's UPS settings (0 = start shutting down straight away).

NAS shutdown time (minutes)

5 minutes is an NTK planning default, not a measurement: time your own NAS.

Reserve (minutes)

Extra margin you want left over.

Result

Runtime at your load (maker's curve, new battery)

Cannot calculate

Runtime you need

Cannot calculate

Load: Cannot calculate

The maker's published runtime points for this model

Load	Runtime

Choosing a UPS? The UPS Sizing Calculator checks every model against your load at once.

How the Estimate Works

The maker's curve. UPS makers publish how long each model runs at different loads with a new, fully charged battery. For APC models NTK reads Schneider Electric's runtime calculator on the Australian product page at a set of loads; for CyberPower models it uses CyberPower's published runtime chart. Your load is placed on that curve: between two published loads the runtime is the straight line between them, the way the makers' charts join their points.

No figure outside the maker's data. Above the highest load the maker publishes, or above the UPS's watt rating, there is no runtime figure. Below the lowest load the maker publishes, NTK does not guess a number either: runtime falls as load rises on every published curve, so the page says runtime is longer than the maker's figure at its lowest load. That covers your need only as an inferred result, labelled as such, because the maker publishes no figure that low. Under 15 W of total load the page cannot tell at all: Schneider says APC Back-UPS models with No-load Shutdown turned on switch off while on battery when the attached load is less than 15 watts, describing a Back-UPS that shuts down after 15 minutes on battery with backup time still left. It applies only to Back-UPS models whose user guide mentions the feature. (APC (Schneider Electric), checked 2026-10-14). NTK does not know which models here have such a cutoff, so it applies to every model.

Your load is the NAS's watts plus everything else on the UPS. A picked NAS uses its maker's busy figure (Synology's Access, QNAP's Operating Mode, Typical and so on), measured under the maker's own conditions; a NAS sitting idle draws less, so its runtime is longer.

Runtime you need = the minutes on battery before the NAS starts shutting down + its shutdown time + any reserve. The verdict compares the two.

Battery age. The figures are for a new battery. No maker publishes a percentage for an older battery, so none is applied: an older battery gives less runtime than shown.

UPS models and their published runtime

Model	Rating	Output on battery	Outlets	USB data port	Maker's runtime (new battery)	Source
CyberPower UT650EG	650 VA 360 W	simulated sine wave, line interactive	3 Australian	No: None listed (no HID USB port, no management cable, no software)	45 min at 50 W, 16 min at 90 W, 5 min at 180 W, 3 min at 200 W, 30 s at 360 W	CyberPower runtime chart, checked 2026-10-08
APC Back-UPS BX750MI-AZ	750 VA 410 W	stepped approximation to a sine wave, line interactive	3 Australian (AS/NZS 3112)	Yes: USB data port (PowerChute Personal Edition)	50 min at 41 W, 26 min at 80 W, 15 min at 125 W, 7.5 min at 200 W, 43 s at 410 W	Schneider Electric runtime calculator on the AU product page, checked 2026-10-08
APC Back-UPS BX950MI-AZ	950 VA 520 W	stepped approximation to a sine wave, line interactive	4 Australian (AS/NZS 3112)	Yes: USB data port (PowerChute Personal Edition)	47 min at 52 W, 28 min at 90 W, 12 min at 175 W, 5 min at 300 W, 28 s at 520 W	Schneider Electric runtime calculator on the AU product page, checked 2026-10-08
CyberPower VP1000ELCD	1000 VA 550 W	simulated sine wave, line interactive	3 Australian	Yes: 1 HID compliant USB port, USB cable, PowerPanel Personal	1 h 6 min at 60 W, 26 min at 137 W, 16 min at 200 W, 9 min at 275 W, 1 min at 550 W	CyberPower runtime chart, checked 2026-10-08
APC Smart-UPS SMT1500IC	1500 VA 1000 W	sine wave, line interactive	8 IEC C13 (not Australian wall sockets) plus 2 IEC jumper cables	Yes: USB and serial ports, SmartConnect port (cloud monitoring)	2 h 52 min at 100 W, 1 h 24 min at 200 W, 40 min at 350 W, 16 min at 600 W, 6.5 min at 1,000 W	Schneider Electric runtime calculator on the AU product page, checked 2026-10-08

Runtime by NAS (the maker's busy figure on each UPS)

NAS (maker's figure)	UT650EG	BX750MI-AZ	BX950MI-AZ	VP1000ELCD	SMT1500IC
Synology DS225+, 16.98 W Access	more than 45 min	more than 50 min	more than 47 min	more than 1 h 6 min	more than 2 h 52 min
Synology DS425+, 28.25 W Access	more than 45 min	more than 50 min	more than 47 min	more than 1 h 6 min	more than 2 h 52 min
Synology DS925+, 37.91 W Access	more than 45 min	more than 50 min	more than 47 min	more than 1 h 6 min	more than 2 h 52 min
Synology DS1823xs+, 87.93 W Access	16 min	23 min	28 min	45 min	more than 2 h 52 min
Synology DS223j, 16.31 W Access	more than 45 min	more than 50 min	more than 47 min	more than 1 h 6 min	more than 2 h 52 min
QNAP TS-464, 40.536 W Operating Mode, Typical	more than 45 min	more than 50 min	more than 47 min	more than 1 h 6 min	more than 2 h 52 min
QNAP TS-264, 29.086 W Operating Mode, Typical	more than 45 min	more than 50 min	more than 47 min	more than 1 h 6 min	more than 2 h 52 min
QNAP TS-433, 22.54 W Operating Mode, Typical	more than 45 min	more than 50 min	more than 47 min	more than 1 h 6 min	more than 2 h 52 min
QNAP TVS-H874, 96.247 W Operating Mode, Typical	15 min	21 min	26 min	41 min	more than 2 h 52 min
UGREEN DXP2800 GT, 42.36 W drive access	more than 45 min	48 min	more than 47 min	more than 1 h 6 min	more than 2 h 52 min
UGREEN DXP4800 GT, 42.36 W drive access	more than 45 min	48 min	more than 47 min	more than 1 h 6 min	more than 2 h 52 min
UGREEN DXP2800, 16.38 W drive access	more than 45 min	more than 50 min	more than 47 min	more than 1 h 6 min	more than 2 h 52 min
UGREEN DH4300 Plus, 22.89 W drive access	more than 45 min	more than 50 min	more than 47 min	more than 1 h 6 min	more than 2 h 52 min
TerraMaster F4-424 Pro, 33.0 W read/write state	more than 45 min	more than 50 min	more than 47 min	more than 1 h 6 min	more than 2 h 52 min
ASUSTOR AS5402T, 22.9 W Operation	more than 45 min	more than 50 min	more than 47 min	more than 1 h 6 min	more than 2 h 52 min

The NAS alone, with nothing else on the UPS. "More than" means the NAS draws less than the lowest load the maker publishes for that UPS, and the figure is the maker's runtime at that lowest load: an inferred result, not a published one. Under 15 W the table says "cannot tell".

Checking your own UPS safely

The Back-UPS BX tests its battery automatically when it is turned on and every 14 days on line, and a long press of the power button runs a manual self test. (APC (Schneider Electric))
Synology DSM supports a UPS connected to the NAS by USB, a network UPS server (another Synology NAS sharing its USB UPS) and an SNMP UPS. (Synology, checked 2026-10-08)
On a power failure a Synology NAS enters Standby Mode after a time you set or when the UPS is low on battery, whichever comes first. (Synology, checked 2026-10-08)
Synology says the UPS power off function varies by brand and model, some UPS devices do not support shutting down by DSM, and to run a power outage simulation test before relying on it. (Synology, checked 2026-10-08)
Set up the NAS's automatic shutdown before any test on battery, and test with the NAS's data safe: a test is the time to find out the settings work, not your files.

Assumptions NTK made

Method last reviewed: 2026-10-14. UPS figures last checked at the makers' Australian sites: 2026-10-08.

Frequently Asked Questions

How long will a UPS keep my NAS running?

It depends on the total load on the UPS and on that model's runtime curve, which the maker publishes for a new, fully charged battery. Synology publishes 87.93 W (Access) for the DS1823xs+; at that load the maker's curves give about 16 min on the UT650EG, about 23 min on the BX750MI-AZ, about 28 min on the BX950MI-AZ and about 45 min on the VP1000ELCD. A smaller NAS can draw less than the lowest load a maker publishes: Synology publishes 28.25 W for the DS425+, below the 50 W where the UT650EG curve starts, so the estimator says only that runtime is longer than the 45 min the maker lists at 50 W. NTK counts that as covering a shutdown only as an inferred fit, listed after models with a published figure at the load. Under 15 W in total it cannot tell at all: Schneider says APC Back-UPS models with No-load Shutdown turned on switch off while on battery when the attached load is less than 15 watts, describing a Back-UPS that shuts down after 15 minutes on battery with backup time still left. It applies only to Back-UPS models whose user guide mentions the feature.

Why not just use the battery's watt hours?

Because runtime does not fall in step with load. CyberPower publishes 28 min at 60 W for the UT650EG but 3 min at 200 W: 3.3 times the load gives about a ninth of the runtime. A battery energy formula cannot show that, so NTK reads each model's published curve and joins neighbouring points with a straight line, the way the makers' charts do. Outside the published loads it gives no figure.

How long does a NAS take to shut down?

It varies from NAS to NAS, so time your own: start a shutdown and note how long it takes to power off. The tools start at 5 minutes, an NTK planning default, not a measurement. Runtime needed = the minutes on battery before the NAS starts shutting down + its shutdown time + any reserve you add. On a power failure a Synology NAS enters Standby Mode after a time you set or when the UPS is low on battery, whichever comes first.

How do I connect a UPS to my NAS for automatic shutdown?

The UPS tells the NAS the power is out over a data cable, usually USB. Synology DSM supports a UPS connected to the NAS by USB, a network UPS server (another Synology NAS sharing its USB UPS) and an SNMP UPS. Of the models here, the maker lists no USB data port for the UT650EG, so it cannot signal a NAS; the BX750MI-AZ, BX950MI-AZ, VP1000ELCD and SMT1500IC each have one. Synology says the UPS power off function varies by brand and model, some UPS devices do not support shutting down by DSM, and to run a power outage simulation test before relying on it. Check your NAS maker's UPS compatibility list for your exact model.

Does a NAS need a pure sine wave UPS?

NTK found no primary source saying a simulated sine wave harms a NAS power supply, so the tools state each model's output as its maker lists it: the UT650EG and VP1000ELCD output a simulated sine wave; the BX750MI-AZ and BX950MI-AZ output a stepped approximation to a sine wave; the SMT1500IC outputs a sine wave. If your NAS or power supply maker asks for sine wave output, tick that requirement in the UPS Sizing Calculator.

What is the difference between VA and watts on a UPS?

Each UPS has two limits on its data sheet, VA (volts times amps) and watts, and the load must stay inside both. For the BX750MI-AZ they are 750 VA and 410 W. A plug-in power meter shows the watts your devices draw; VA is higher when a power supply's power factor is below 1, and only a meter that shows VA can measure it, so the sizing calculator tests the VA limit only when you enter a measured VA. It does not assume a power factor.

When should I replace the UPS battery?

APC says the battery typically lasts three to five years, and that high temperatures, high humidity, poor quality mains power and frequent short discharges shorten its life. The makers list the battery in the UT650EG, BX750MI-AZ, BX950MI-AZ and VP1000ELCD as not user replaceable. The SMT1500IC takes the RBC7 replacement battery cartridge. The Back-UPS BX tests its battery automatically when it is turned on and every 14 days on line, and a long press of the power button runs a manual self test.

Does an older battery give less runtime?

CyberPower's runtimes are from testing fully charged, new batteries at normal operating conditions; it says runtime is approximate and varies with battery age, charge, environment and other variables. APC says batteries need recharging after long outages and wear out faster when put into service often or run hot. NTK applies no percentage for battery age because no maker publishes one: the runtime shown is the maker's new battery figure, so an older battery gives less. To check yours, use the UPS's self test or a planned outage test with the NAS's shutdown already set up.

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