Home Battery Option Calculator

Use this tool to compare a subsidy-efficient battery around 27–28 kWh against a larger resilience-focused battery around 40 kWh. The calculator uses the federal battery STC settings that apply before 1 May 2026 and from 1 May 2026 onward.

This is an assessment tool only. It does not replace written advice from an accredited installer, retailer or tax adviser. It assumes a residential battery installed with eligible solar PV under the Australian federal program and applies NSW VPP size logic as a guide only.

For advice on commercial or residential energy solutions email info@haronrobson.com.au

Option A

Use this for a typical smaller or mid-sized battery option.

Option name

Installation timing

Usable battery capacity (kWh)

Quoted installed price before rebate (A$)

Extra site costs not in quote (A$)

Working STC value (A$ per STC)

Assumed NSW VPP incentive (A$)

Average daily battery use target (kWh/day)

Option B

Use this for a larger whole-home backup or EV-support battery option.

Option name

Installation timing

Usable battery capacity (kWh)

Quoted installed price before rebate (A$)

Extra site costs not in quote (A$)

Working STC value (A$ per STC)

Assumed NSW VPP incentive (A$)

Average daily battery use target (kWh/day)

Comparison summary

The outputs below are calculated from your assumptions. The federal discount estimate is STC-based. NSW VPP treatment is flagged as a practical guide only and should be confirmed with the provider in writing.

Better net cost

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Better subsidy efficiency

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Longer autonomy

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Timing sensitivity

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Measure	Option A	Option B
Usable capacity
Estimated STCs
Estimated federal discount
Quoted installed price
Extra site costs
NSW VPP incentive used
Estimated out-of-pocket cost
Net cost per usable kWh
Approx. days of storage at target use
NSW VPP size check
Recommendation signal

Notes and rules to watch

The federal timing test is the date of the electrical certificate of compliance, not the date of quote, deposit or contract.
For January to April 2026, the calculator uses an STC factor of 8.4.
For 1 May 2026 onward, the calculator uses an STC factor of 6.8 with tapering: 0–14 kWh at 100%, 14–28 kWh at 60%, and 28–50 kWh at 15%.
The federal calculation only counts the first 50 kWh usable even if the battery is larger.
The NSW VPP size position around exactly 28 kWh should be treated carefully and confirmed in writing.
Only one federal battery claim is generally available per premises once an eligible system has already claimed STCs.