UPS · VA & WATT CHECK
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BLACKOUT READINESS CHECK

Free interactive calculator · preloaded example

Will your NBN router + PC stay on in a blackout?

Check whether they will stay on by comparing both VA and watts before you buy. Then see an idealised battery-runtime estimate using your own inputs.

A 650 VA label alone cannot answer that question. Check the exact model ratings.

Check my setup
A desktop computer, Wi-Fi router and unbranded UPS in a dim home office during a power outage

Enter your setup

The example is pre-filled. Change any value and the result updates as you type.

Connected load and UPS ratings
Use measured or nameplate watts.
Use the equipment spec if known.
Read the exact model label/manual.
Battery bank and estimation assumptions
Enter total bank Ah at the stated discharge rate.
Use the battery datasheet rating, often C20.
Adjust only with reliable model data.
Changing chemistry may not be approved by your UPS maker.
Prefer the battery manufacturer's value.
This only adds words to retailer searches; it does not identify a compatible SKU.
How the estimate is calculated

Apparent power: VA = load watts ÷ power factor. The 25% headroom check is shown as a planning target. The connected load must remain under both the UPS model's VA and watt limits.

DC current: I = load watts ÷ (battery bus volts × assumed DC-to-AC efficiency).

Idealised Peukert time: t = H × (Irated ÷ Iload)n, where Irated = battery Ah ÷ rating hours. This rough model does not reproduce a UPS manufacturer's test curve.

Your estimate

Illustrative result · based on current inputsChecking the two UPS ratings…

Use the manufacturer's published model limits before connecting equipment.

Search relevant AU listings

These are retailer search links, not a checked price comparison. Confirm the exact product, seller, delivery and fit on the retailer site.

amazonAustralia search
Illustrative category image; product results may differ.Search Amazon AU

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eBayAustralia listings
Looking for current eBay AU matches…

An API-returned listing may include an eBay Partner Network link. The fallback search is EPN-tracked when a current item match is unavailable.

Apparent load—VA from watts ÷ PF
VA planning target—Load VA × 1.25
Watt planning target—Load watts × 1.25
Estimated DC current—Uses the efficiency input
Idealised Peukert runtime—Estimate, not a product runtime promise
Entered UPS rating—Compare exact datasheet ratings
Battery match is not verified. A voltage, Ah value and terminal clue do not establish fit. Check the UPS manufacturer's battery cartridge, chemistry, pack wiring, dimensions, connector polarity and installation instructions.

No IP location is read and the market is not switched automatically. Example market: Australia (AUD). Price, availability, shipping and seller details are not guaranteed.

Before relying on a UPS estimate

Reference: APC UPS sizing guide · Victron battery capacity and Peukert exponent · CyberPower model runtime charts.

Common questions

Does a 650 VA label alone prove a UPS can handle this load?

No. Check the model's separate VA and watt output limits, and allow appropriate headroom. Do not infer overload from the VA number alone.

Is the runtime exact?

No. It is a simplified estimate. The UPS model's tested runtime chart is the better source for a real setup.

Does the battery clue guarantee a matching replacement?

No. Confirm the approved cartridge and physical/electrical specifications in the UPS manual.

Watch the UPS calculator walkthrough

A quick hook, then a full walkthrough. See how the example values become separate VA and watt planning targets.

15-second quick check

45-second walkthrough

Related eBay AU listing

Checking for a current eBay listing…

Search matches are not verified for exact product fit.
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Frequently asked questions

Does a 650 VA UPS always fail with a 450 W computer?

No. Check the specific UPS model's separate output-watt and VA ratings, the connected load, power factor and manufacturer guidance. The VA label alone does not determine whether the load is supported.

Is the runtime result the exact time my UPS will run?

No. It is a simplified estimate using battery capacity, reference discharge rate, Peukert exponent and conversion efficiency. Battery age, temperature, cutoff voltage, load variation and the UPS runtime curve affect actual time.

Does the battery specification prove a replacement will fit?

No. Confirm the UPS model's approved battery cartridge, chemistry, voltage, capacity, dimensions, terminal type and polarity in its official manual before purchasing.