What's the difference between VA and watts on a UPS?

VA (volt-amperes) is the apparent power, the maximum the UPS can deliver in theory. Watts is the real power your devices actually consume. A 1000VA UPS might only deliver 550-600 watts of real power. Neither VA nor watts tells you battery capacity, that's measured in Wh (watt-hours), which is what determines runtime.

How long does a NAS need to shut down safely?

Most modern Synology and QNAP NAS units complete a clean shutdown in 1-2 minutes. Larger arrays with many active services or parity checks may take 3-5 minutes. Configure auto-shutdown even if your UPS seems large enough, an unclean shutdown can corrupt files and break RAID arrays.

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

Most consumer UPS units connect via USB. Synology supports this natively in Control Panel → Hardware & Power → UPS. QNAP has similar built-in support. Configure the NAS to shut down automatically when battery reaches a threshold (e.g., 30%) or after a set time on battery.

Should I put my router and modem on the UPS too?

Yes, if you want your NAS to remain reachable during an outage. A modem and router together draw about 15-20 W, which modestly impacts runtime but keeps your network alive for monitoring, alerts, and remote shutdown commands.

Can a UPS damage my NAS?

No. A UPS only provides clean, conditioned power. The opposite scenario is the risk: without a UPS, power events like brownouts, surges, and outages can corrupt NAS data, damage drives, and interrupt RAID rebuilds. Line-interactive UPS units also provide voltage regulation during brownouts.

Line-interactive vs standby vs online, which UPS type for a NAS?

For home NAS use, line-interactive is the sweet spot. It corrects minor voltage fluctuations without switching to battery (extending battery life) and switches to battery in 2-5 ms. Standby UPS units are cheaper but switch slower (5-12 ms). Online (double-conversion) UPS units are overkill and less efficient for a home NAS.

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

Q: When should I replace UPS batteries?

Lead-acid UPS batteries typically last 3-5 years. Signs of a failing battery: the UPS beeps or shows a 'replace battery' indicator, runtime drops noticeably, or the UPS fails during an outage. Replacement batteries for consumer units cost $30-80 AU and are a straightforward swap.

This UPS runtime estimator for NAS calculates how long your uninterruptible power supply will keep your NAS running during a power outage based on UPS capacity, NAS wattage, and battery age. Helps you decide if your current UPS provides adequate protection.

Estimate how long your UPS will keep your NAS running during a power outage, and whether that's enough time for a safe shutdown.

Power outages don't damage a NAS directly, but an unclean shutdown can corrupt files, break RAID arrays, and interrupt backup jobs. A UPS gives your NAS time to shut down gracefully, but only if the battery has enough capacity for your load.

Not sure how many watts your NAS draws? Use our NAS Power Cost Calculator to estimate consumption, then come back with the number.

Your Setup

NAS Model

NAS power draw (W) That's high for a NAS, make sure you're entering NAS consumption only, not the whole rack.

Other Devices on UPS (optional)

Modem / Router W

Network Switch W

Other W

Total load

35 W NAS only

UPS Model

VA rating

Max watts

Battery capacity (Wh) Wh = V × Ah. Check the battery label or search "[your UPS model] battery Wh".

Battery age

NAS shutdown time needed Most modern Synology and QNAP units shut down in 1-2 minutes. If unsure, choose 2 minutes.

Results

Age-adjusted runtime
—

Full-battery runtime

—

at new battery

UPS load —

Tips for Your Setup

Runtime formula: Runtime (minutes) = (Battery Wh × age factor × efficiency factor) ÷ total load (W) × 60

Battery Wh values for preset UPS models are sourced from manufacturer specifications. The age factor accounts for lead-acid battery degradation over time (new = 100%, 1-2 yr = 90%, 3-4 yr = 75%, 5+ yr = 55%). The efficiency factor adjusts for real-world inverter losses, which vary by load percentage: UPS units are most efficient between 40-60% load.

These are estimates. Actual runtime depends on battery condition, ambient temperature, input voltage stability, and UPS firmware behaviour. We use conservative efficiency values so real-world results should meet or exceed these estimates. For exact runtime, test with your actual hardware by timing how long the UPS holds your load during a planned power-off.

Frequently Asked Questions

VA (volt-amperes) is the apparent power, the maximum the UPS can deliver in theory. Watts is the real power your devices actually consume. The ratio between them is the power factor (typically 0.6-0.7 for consumer UPS units). A 1000VA UPS might only deliver 550-600 watts of real power. Always check the watt rating, not just VA, when sizing a UPS. Neither VA nor watts tells you battery capacity, that's in Wh (watt-hours), which is what determines runtime.

Most modern Synology and QNAP NAS units complete a clean shutdown in 1-2 minutes. This includes flushing write caches, closing open files, stopping services, and parking drive heads. Larger arrays with many active services or parity checks in progress may take 3-5 minutes. The risk of an unclean shutdown is file corruption, broken RAID arrays, and interrupted backup jobs, so configure auto-shutdown even if your UPS seems large enough.

Most consumer UPS units (APC, CyberPower) connect to a NAS via USB. Synology supports this natively in Control Panel → Hardware & Power → UPS. QNAP has similar built-in support under Control Panel → System → UPS. Configure the NAS to shut down automatically when battery reaches a threshold (e.g., 30%) or after a set time on battery. Synology also supports "network UPS" mode where one device acts as the UPS server for others on the same network.

Lead-acid UPS batteries typically last 3-5 years depending on usage, temperature, and discharge frequency. Signs of a failing battery: the UPS beeps or shows a "replace battery" indicator, runtime drops noticeably, or the UPS fails to hold load during an outage. Replacement batteries for consumer UPS units cost $30-80 AU and are a straightforward swap on most models. Test annually by unplugging the UPS from the wall and timing how long it holds your load.

Yes, if you want your NAS to remain reachable during an outage. A modem and router together draw about 15-20 W, a modest impact on runtime, but it keeps your network alive. This means you can receive NAS shutdown alerts, access your NAS remotely to check status, and allow cloud backup services to complete or pause gracefully. Use the "Modem / Router" checkbox above to see the impact on your runtime.

For a typical 2-4 bay home NAS (25-40 W), a 600VA / 330W UPS gives roughly 30-75 minutes of runtime on a charged battery, far more than the 1-3 minutes needed for a clean shutdown. If you're also powering a router and switch, step up to 750VA-1000VA for comfortable headroom. The goal isn't to run for hours, it's to give the NAS enough time to shut down cleanly and ride through brief outages (which are most outages). Use this estimator to check your specific setup before buying.

No. A UPS only provides clean, conditioned power to your devices. The opposite scenario is the real risk: without a UPS, power events like brownouts, surges, and sudden outages can corrupt NAS data, damage drives, and interrupt RAID rebuilds. Line-interactive UPS units also provide voltage regulation during brownouts, adding another layer of protection beyond just battery backup. There's essentially no downside to running a NAS on a UPS.

For home NAS use, line-interactive is the sweet spot. It corrects minor voltage fluctuations without switching to battery (extending battery life) and switches to battery in 2-5 ms, fast enough that a NAS power supply won't notice. Standby UPS units are cheaper but switch slower (5-12 ms) and don't regulate voltage. Online (double-conversion) UPS units provide the cleanest power with zero transfer time, but they're expensive, less efficient, and generate more heat, overkill for a home NAS. Most APC BX and CyberPower VP models sold in Australia are line-interactive.

AU UPS Pricing Reference: NAS Protection (early 2026)

UPS units suitable for NAS protection in Australia. AU power standard: 240V, 50Hz. Prices from Mwave, PLE, Amazon AU.

UPS	Capacity	AU retail (approx)	Best for
APC BX950MI	950VA / 520W	$160-$200	2-bay NAS + switch: 15-25 min runtime at 60W load
APC BX1600MI	1600VA / 900W	$280-$340	4-bay NAS + router + switch: 20-35 min at 80W load
CyberPower CP1500EPFCLCD	1500VA / 900W	$300-$380	Pure sine wave, recommended for NAS with sensitive PSUs
APC SMT1000I	1000VA / 700W	$400-$500	Smart UPS: USB management, Synology/QNAP UPS integration
Eaton 5E 1200	1200VA / 720W	$180-$230	Budget option, adequate for single NAS + switch

AU Power Outage Context

Australian power outages are typically brief, most outages last under 30 minutes. A UPS for NAS does not need to power the NAS indefinitely; it needs to provide enough runtime to either:

Ride out short outages (most AU residential outages): 10-20 minutes coverage is usually sufficient
Trigger a clean shutdown via USB or network UPS communication, most Synology and QNAP units support APC and CyberPower USB integration natively

For Sydney, Melbourne, and Brisbane, the average grid outage duration is under 60 minutes per year (AER distribution reliability data). A 950VA UPS provides adequate protection for most AU home NAS users.

AU pure sine wave note: Most AU NAS units with switching power supplies work with simulated sine wave (AVR) UPS output. However, for NAS units with active PFC power supplies (check your NAS spec sheet), a pure sine wave UPS is required, simulated sine wave can cause shutdown or PSU damage. When in doubt, choose pure sine wave (e.g., CyberPower CP1500EPFCLCD or APC SMT series).