Do I need line-interactive or standby UPS?

For home NAS use, line-interactive is strongly preferred. It corrects minor voltage fluctuations without switching to battery and transfers to battery in 2-5 ms. Standby UPS units are cheaper but switch slower (5-12 ms) and don't regulate voltage. Most APC Back-UPS BX and CyberPower VP models sold in Australia are line-interactive.

UPS Sizing Calculator for NAS — What VA Rating Do You Need?

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

VA (volt-amperes) is the apparent power rating. Watts is the real power your devices consume. The ratio between them is the power factor (typically 0.6-0.7 for consumer UPS units). A 1000 VA UPS delivers roughly 550-600 watts of real power. For NAS sizing, watts matters more for runtime calculations, but VA determines whether the UPS can handle startup surge.

This UPS sizing calculator for NAS recommends the minimum VA rating and wattage you need based on your NAS model, drive count, network switch, and desired runtime. Prevents buying an undersized UPS that trips under real load.

Figure out what size UPS you need for your NAS — before you buy. Enter your NAS model, drives, and any other devices on the UPS, and we'll recommend a specific VA rating and models available in Australia.

Most NAS users skip the UPS until after an outage causes data loss. A properly sized UPS gives your NAS time to shut down cleanly during a power cut, ride through brief outages entirely, and protects drives from surge damage.

Already own a UPS? Use our UPS Runtime Estimator to check if it's adequate for your specific setup.

Your Setup

NAS Model

Load Watts (worst case)

Number of HDDs

HDDs draw ~25 W extra on spinup. The UPS must handle this peak.

Additional Devices on UPS

Modem/Router W

Switch (unmanaged) W

Switch (managed/PoE) W

Monitor W

Other W

Desired Runtime on Battery

Recommendation

Calculating…

VA requirement from surge calculation is modest, but we recommend a minimum 600 VA for adequate battery capacity and runtime. Runtime is the binding constraint for most home NAS setups, not surge handling.

Recommended VA
—
with 25% headroom

Minimum VA

—

floor applies if below 600

Steady Load

—

running watts

Required Wh

—

for target runtime

Recommended AU Models

Step 1: Steady-state load = NAS load watts + all checked device watts.

Step 2: Peak surge = steady load + (HDD count × 25 W). HDDs draw ~25 W extra on spinup.

Step 3: Minimum VA = peak surge ÷ 0.65 (conservative power factor), rounded up to next 50 VA.

Step 4: Recommended VA = minimum VA × 1.25 (25% headroom), rounded to next 50 VA. A 600 VA floor applies, runtime, not surge, is usually the binding constraint for home NAS.

Step 5: Required Wh = (steady load × desired minutes ÷ 60) ÷ 0.85 (line-interactive efficiency at typical load). This tells you how much battery capacity you need.

AU power note: Australian mains power is 230V/50Hz. All UPS models listed are compatible. APC and CyberPower are the dominant brands in AU, both with local warranty through Australian distributors. Rates verified March 2026.

AU Reference: Common NAS UPS Setups

Approximate recommendations for common AU home NAS configurations. All prices AUD incl. GST, sourced from Mwave/Scorptec March 2026.

Setup	Load (W)	Recommended VA	~Runtime (10 min battery)	AU Price
2-bay NAS only	22 W	600 VA	18 min	~$110
2-bay NAS + router	37 W	600 VA	11 min	~$110
4-bay NAS + router + switch	63 W	750 VA	10 min	~$140
4-bay NAS + router + switch + modem	73 W	750 VA	8 min	~$140
6-bay prosumer + full network	95 W	1000 VA	10 min	~$160
8-bay + full network	120 W	1000 VA	8 min	~$160

AU UPS Models (APC & CyberPower)

Model	VA	Type	AU Price (approx)	Retailer
APC BE600G	600 VA	Line-interactive	~$110	Mwave / Scorptec
APC BX750MI	750 VA	Line-interactive	~$140	Mwave / Scorptec
APC BX950MI	950 VA	Line-interactive	~$180	Mwave / Scorptec
CyberPower UT650EG	650 VA	Line-interactive	~$100	Umart
CyberPower VP1000ELCD	1000 VA	Line-interactive	~$160	Mwave

AU Retailers

Retailer	URL	Notes
Mwave	mwave.com.au	Best range APC/CyberPower, usually cheapest
Scorptec	scorptec.com.au	Good stock, Sydney/Melbourne pickup
Umart	umart.com.au	Budget alternatives, CyberPower strong
Centrecom	centrecom.com.au	Good for APC warranty/support

Prices approximate, sourced from Mwave/Scorptec March 2026. All prices AUD incl. GST. Formula: VA = peak load (including HDD spinup surge) ÷ 0.65, rounded up to next 50. Australian mains power is 230V/50Hz. APC and CyberPower both carry local AU warranty.

Frequently Asked Questions

For a typical 2–4 bay home NAS with a router, a 600–750 VA UPS is adequate. This gives you 10–15 minutes of runtime — enough to ride through most outages and shut down cleanly. If you're running a 6–8 bay NAS with multiple network devices, step up to 1000 VA for comfortable headroom. Use this calculator to check your specific setup — VA requirements vary significantly based on HDD count and attached devices.

VA (volt-amperes) is the apparent power rating — what the UPS can theoretically deliver. Watts is the real power your devices consume. The ratio between them is the power factor (typically 0.6–0.7 for consumer UPS units). A 1000 VA UPS delivers roughly 550–600 watts of real power. For NAS sizing, the watts rating matters more than VA for runtime calculations — but VA determines whether the UPS can handle startup surge.

Hard drives draw significantly more power on spinup than during normal operation — about 25 W per drive for 2–3 seconds on startup. If all your drives spin up simultaneously (which happens on NAS boot), the UPS needs to handle this surge without shutting down or switching to battery. This is why we include HDD spinup surge in the VA calculation, even if steady-state load is modest.

For home NAS use, line-interactive is strongly preferred. It corrects minor voltage fluctuations without switching to battery (extending battery life) and transfers to battery in 2–5 ms — fast enough that the NAS doesn't notice. Standby UPS units are cheaper but switch slower (5–12 ms) and don't regulate voltage. Most APC Back-UPS BX and CyberPower VP models sold in Australia are line-interactive.

The best options for AU NAS users are Mwave (mwave.com.au), Scorptec (scorptec.com.au), and Umart (umart.com.au). All three carry APC and CyberPower with local AU warranty. Mwave and Scorptec typically have the widest range; Umart often has the best prices on CyberPower budget models. All products carry 12-month Australian Consumer Law warranty as a minimum.

Most consumer UPS units connect via USB. Synology supports this in Control Panel → Hardware & Power → UPS. QNAP has similar built-in support. Configure auto-shutdown to trigger at 30% battery remaining or after a set time on battery (e.g., 2 minutes). This ensures a clean shutdown even if you're not home to intervene. See our UPS Runtime Estimator to verify your shutdown timing gives adequate margin.

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