How do I calculate how many STCs my solar system will create?

The formula is: STCs = system capacity (kW) × zone rating × deeming period (years to 2030). Find your zone rating from the table below using your postcode or state. In 2026, the deeming period is 4 years. Multiply your system size (kW) by your zone rating and by 4 to get the approximate STC count. For the official count, use the Clean Energy Regulator's STC calculator at cleanenergyregulator.gov.au.

How much is my STC discount worth in dollars?

Multiply the number of STCs your system creates by the current STC market price (approximately $35–40 per STC in 2026). For example, 36 STCs × $38 = $1,368 discount on a 6.6 kW system in Sydney. For a 10 kW system in Brisbane (Zone 2): approximately 61 STCs × $38 = $2,318 discount. The actual discount depends on the STC price at the time your installer sells the certificates.

Zone 1 (highest multiplier — 1.622): Darwin, Katherine, Tennant Creek in NT; Cairns, Townsville, Mt Isa in QLD. Zone 2 (multiplier 1.536): Brisbane and most of QLD; Adelaide and most of SA; most of WA east of the coast; Broken Hill and far west NSW. Zone 3 (multiplier 1.382): Sydney, Newcastle, Wollongong, Canberra; Melbourne and most of VIC; Perth metropolitan area; coastal SA. Zone 4 (lowest — 1.185): Hobart and most of TAS; Gippsland and eastern VIC.

Can I create STCs myself rather than assigning them to the installer?

Yes. You can register the system yourself in the REC Registry (recregistry.gov.au) and create the STCs in your own account. You then sell them on the broker market or through the government clearing house. However, this process takes time (the clearing house can take months) and requires registering as a participant in the registry. Most customers find it simpler and faster to assign to the installer for an immediate upfront discount.

STC Zone Map & Calculator

Q: Does the STC value reduce each year?

Yes. The deeming period reduces by 1 year each January 1. In 2026 it is 4 years; in 2027 it will be 3 years; in 2028 it will be 2 years. A 6.6 kW system in Sydney creates approximately 36 STCs in 2026 but only 27 STCs in 2027 — a reduction of about $350 in upfront discount value. This is a legitimate urgency factor for customer proposals.

The STC discount is often the first question Australian solar customers ask — “how much is the rebate?” This guide provides the zone ratings, STC lookup tables by system size, and dollar value calculations to answer that question accurately for any Australian location and system size.

STC Formula

STCs = System kW × Zone Rating × Deeming Period (years)

Deeming Period (2026)

4 years (scheme ends December 31, 2030)

STC Market Price (approx.)

$35–40 AUD per STC (broker market, 2026)

Clearing House Price

$40 AUD (guaranteed floor — slower settlement)

Official Calculator

Clean Energy Regulator — STC Calculator

Certificate Registry

recregistry.gov.au

STC Zone Map: Zone by State and Region

State/Territory	Region	STC Zone	Zone Rating
Northern Territory	All of NT (Darwin, Katherine, Alice Springs)	Zone 1	1.622
Queensland	Cairns, Townsville, Mt Isa, Mackay (far north)	Zone 1	1.622
Queensland	Brisbane, Gold Coast, Sunshine Coast, Toowoomba, Rockhampton	Zone 2	1.536
South Australia	Outback and inland SA (Broken Hill area, Port Augusta)	Zone 2	1.536
South Australia	Adelaide metropolitan and coastal SA	Zone 3	1.382
Western Australia	Pilbara, Kimberley, inland WA	Zone 2	1.536
Western Australia	Perth metropolitan and SW coastal WA	Zone 3	1.382
New South Wales	Far west NSW (Broken Hill, Tibooburra)	Zone 2	1.536
New South Wales	Sydney, Newcastle, Wollongong, Central Coast	Zone 3	1.382
Australian Capital Territory	Canberra and surrounds	Zone 3	1.382
Victoria	Melbourne metropolitan, Geelong, Ballarat	Zone 3	1.382
Victoria	Gippsland, eastern highlands, southern VIC	Zone 4	1.185
Tasmania	All of Tasmania (Hobart, Launceston, Devonport)	Zone 4	1.185

Note: Zone boundaries can vary within states. Use the Clean Energy Regulator’s postcode lookup for exact zone confirmation.

STC Count by System Size: Zone 3 (Sydney / Melbourne / Perth)

Deeming period: 4 years (2026). Zone rating: 1.382.

System Size	STCs Created	Value at $37/STC	Value at $39/STC
3 kW	17 STCs	$629	$663
5 kW	28 STCs	$1,036	$1,092
6.6 kW	36 STCs	$1,332	$1,404
10 kW	55 STCs	$2,035	$2,145
13.2 kW	73 STCs	$2,701	$2,847
20 kW	111 STCs	$4,107	$4,329
30 kW	166 STCs	$6,142	$6,474

STC Count by System Size: Zone 2 (Brisbane / Adelaide / Most of WA)

Deeming period: 4 years (2026). Zone rating: 1.536.

System Size	STCs Created	Value at $37/STC	Value at $39/STC
3 kW	18 STCs	$666	$702
5 kW	31 STCs	$1,147	$1,209
6.6 kW	41 STCs	$1,517	$1,599
10 kW	61 STCs	$2,257	$2,379
13.2 kW	81 STCs	$2,997	$3,159
20 kW	123 STCs	$4,551	$4,797
30 kW	184 STCs	$6,808	$7,176

STC Count by System Size: Zone 1 (Darwin / Far North QLD)

Deeming period: 4 years (2026). Zone rating: 1.622.

System Size	STCs Created	Value at $37/STC	Value at $39/STC
3 kW	19 STCs	$703	$741
5 kW	32 STCs	$1,184	$1,248
6.6 kW	43 STCs	$1,591	$1,677
10 kW	65 STCs	$2,405	$2,535
13.2 kW	86 STCs	$3,182	$3,354
20 kW	130 STCs	$4,810	$5,070

STC Count by System Size: Zone 4 (Tasmania / Southern VIC)

Deeming period: 4 years (2026). Zone rating: 1.185.

System Size	STCs Created	Value at $37/STC	Value at $39/STC
3 kW	14 STCs	$518	$546
5 kW	24 STCs	$888	$936
6.6 kW	31 STCs	$1,147	$1,209
10 kW	47 STCs	$1,739	$1,833
13.2 kW	63 STCs	$2,331	$2,457
20 kW	95 STCs	$3,515	$3,705

How Deeming Period Reduction Affects Value

The reduction in STC value as the scheme approaches 2030 is significant for customer decision-making:

Year	Deeming Period	STCs (6.6 kW, Zone 3)	Value at $38/STC
2026	4 years	36 STCs	$1,368
2027	3 years	27 STCs	$1,026
2028	2 years	18 STCs	$684
2029	1 year	9 STCs	$342

A customer who delays solar from 2026 to 2027 loses approximately $342 in STC value on a 6.6 kW Zone 3 system. This is a factual and legitimate point to include in proposals.

Pro Tip: STC Value Should Be Shown as a Separate Line in Every Proposal

Show the STC calculation transparently: “36 STCs × $38 = $1,368 STC discount.” Customers who understand exactly how the discount is calculated are more confident buyers than customers who see a vague “government rebate.” Use solar proposal software that automatically calculates STC count by zone and displays the value clearly in the financial summary.

Net System Cost Examples After STC Discount

Using a gross installed cost of $1,000/kW (mid-market 2026 pricing for a standard grid-connected system with quality components):

System	Location	Gross Cost	STC Value	Net Cost
6.6 kW	Sydney (Zone 3)	$6,600	$1,368	$5,232
6.6 kW	Brisbane (Zone 2)	$6,600	$1,558	$5,042
6.6 kW	Darwin (Zone 1)	$6,600	$1,636	$4,964
10 kW	Sydney (Zone 3)	$10,000	$2,090	$7,910
10 kW	Brisbane (Zone 2)	$10,000	$2,318	$7,682
13.2 kW	Melbourne (Zone 3)	$13,200	$2,774	$10,426

Payback Period with STC Discount

Using the net cost after STC and typical annual savings:

System	Location	Net Cost	Annual Savings (est.)	Payback
6.6 kW	Sydney	$5,232	$1,800–2,200	2.4–2.9 years
6.6 kW	Brisbane	$5,042	$1,900–2,300	2.2–2.7 years
6.6 kW	Melbourne	$5,232	$1,600–2,000	2.6–3.3 years
10 kW	Sydney	$7,910	$2,700–3,300	2.4–2.9 years

Annual savings assume retail electricity rate of $0.28–0.35/kWh, 70–80% self-consumption, feed-in tariff of $0.06–0.10/kWh for export.

Calculate Accurate STC Values for Every Australian Solar Proposal

SurgePV calculates the correct STC count by zone and deeming period, incorporates the STC discount into the financial model, and shows customers net cost, payback period, and 25-year savings in a single proposal output.

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Frequently Asked Questions

How do I calculate my STC count?

System kW × zone rating × 4 (deeming period in 2026). Zone 1: 1.622; Zone 2: 1.536; Zone 3: 1.382; Zone 4: 1.185.

What is the STC dollar value?

STCs × current market price (~$35–40 in 2026). A 6.6 kW Sydney system creates about 36 STCs worth approximately $1,300–1,400.

Does the STC value reduce each year?

Yes — by approximately 25% per year as the deeming period reduces from 4 (2026) to 1 (2029). Systems installed in 2026 receive the highest remaining STC value.

Can I sell my STCs myself?

Yes, through the REC Registry and clearing house. Most customers assign to the installer for an immediate upfront discount instead.

What zone is my postcode?

Use the Clean Energy Regulator’s postcode lookup at cleanenergyregulator.gov.au for the exact zone. The table above gives guidance by region — confirm with the official tool for any customer proposal.