Where do the starting figures come from?

From you. Every starting figure and the surge rating are entered from the appliance, inverter or battery documentation. Wattbench supplies no typical figure and applies no starting multiplier, because starting behaviour is product-specific.

Why is a load left out when its unit differs from the rating?

Converting between amps, kVA and kW needs a voltage and a power factor that only the product documentation can give. The worksheet does not assume one, so a load in a different unit is not compared and not added to the simultaneous start. Convert it using the product documentation and re-enter it.

What if a load has no published starting figure?

Mark it as having no published figure. It is shown as unknown rather than counted as zero, and it is listed as missing from the simultaneous start. This is common with inverter-drive compressors, so confirm the starting behaviour with the manufacturer.

Does a result within the rating mean the backup will hold?

No. It is an arithmetic comparison against the rating you entered. Inrush profile and duration, simultaneous starts and the product's own protection govern what actually happens, and a start that lasts longer than the entered surge duration is not covered by the comparison.

The calculation runs in your browser. Keep with this job stores a dated snapshot on this device without an account. Nothing is sent to Wattbench unless you sign in and deliberately select Save result. Local snapshots are not a backup.

Backup Worksheet

Essential Load Schedule

Turn entered continuous loads and daily run-times into a backup power and energy schedule, then compare each load's starting demand with the backup system's own surge rating.

Sources listedReviewed September 2026Our methodology

Inputs

View result

Always-on load

Always-on hours per day

Cycled load

Cycled hours per day

Live result

Edit inputs

Concurrent load

1.6kW

Daily energy

13.2kWh

List individual circuits in the job record. Compare starting demand with the backup surge rating in the starting-load check below.

Starting-load check

Compare motor, compressor and pump starting demand with the backup system's own surge rating. Take every figure from the inverter, battery or appliance documentation. Nothing here is pre-filled or assumed.

Starting inputs

View check

Backup system surge rating

Surge ratingFrom the inverter or battery documentation.

Rating unit

Surge durationHow long the documented surge rating applies.

Loads that start on backup

Load 1

Load name

Starting demandThe published starting figure for this load.

Starting demand unit

No published starting figureMay start at the same time as others

Already running at the moment of start (optional)Uses the surge rating's unit. Leave blank to leave it out.

Starting-load comparison

Enter the backup surge rating, unit and duration to compare.

Per load

Load 1
Choose the unit the starting figure is published in

Worst-case simultaneous start

Enter the backup surge rating, unit and duration to compare.

Inrush profile and duration, simultaneous starts and the product's own protection govern the real outcome. A start that lasts longer than the entered surge duration is not covered by this comparison. Units are never converted.

Key takeaways

Totals the entered continuous loads and their daily run-times into concurrent power and daily energy.
Compares each motor, compressor or pump's entered starting demand, and the loads that may start together, with the surge rating you enter from the inverter or battery documentation.
Never converts between amps, kVA and kW, and never supplies a starting figure. A load without a published figure is shown as unknown, not as zero.

How it works

Continuous power is the sum of loads assumed to run together. Daily energy is each entered load multiplied by its run-time.

The starting-load check compares each load's entered starting demand with the backup system's entered surge rating, only where both use the same unit. Loads marked as able to start together are added, with any already-running load, and compared the same way. Amps, kVA and kW are never converted into each other, and no starting figure is supplied or assumed: appliance and backup behaviour is product-specific.

Related standards: AS/NZS 5139 and AS/NZS 4777.1. This worksheet does not apply either standard.

Estimates only: for guidance, not a quote or a compliance certificate. Verify against the current AS/NZS standards and a licensed design. The maths runs in your browser. Nothing is sent to Wattbench unless you sign in and deliberately save the result.

Source ledger2 sources

RegulatorBatteries — Australian Government Solar Consumer Guide
Standards bodyAS/NZS 5139:2019 — Standards Australia catalogue

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Good to know

Frequently asked

Where do the starting figures come from?: From you. Every starting figure and the surge rating are entered from the appliance, inverter or battery documentation. Wattbench supplies no typical figure and applies no starting multiplier, because starting behaviour is product-specific.
Why is a load left out when its unit differs from the rating?: Converting between amps, kVA and kW needs a voltage and a power factor that only the product documentation can give. The worksheet does not assume one, so a load in a different unit is not compared and not added to the simultaneous start. Convert it using the product documentation and re-enter it.
What if a load has no published starting figure?: Mark it as having no published figure. It is shown as unknown rather than counted as zero, and it is listed as missing from the simultaneous start. This is common with inverter-drive compressors, so confirm the starting behaviour with the manufacturer.
Does a result within the rating mean the backup will hold?: No. It is an arithmetic comparison against the rating you entered. Inrush profile and duration, simultaneous starts and the product's own protection govern what actually happens, and a start that lasts longer than the entered surge duration is not covered by the comparison.
Is my data stored?: The calculation runs in your browser. Keep with this job stores a dated snapshot on this device without an account. Nothing is sent to Wattbench unless you sign in and deliberately select Save result. Local snapshots are not a backup.

Keep calculating