20 kW solar system cost in Australia, October 2026
The national standard offer for a 20 kW system is $18,659 and the premium offer is $22,254 in October 2026, after the STC discount and including GST, or 0.93 to 1.11 dollars per watt; basis: derived: the residential 10 kW figure scaled by the Solar Choice commercial index ratio between 10 kW and 30 kW (this city, August 2026); no residential index exists at 20 kW. These are Solar Choice installer offers, not quotes received by homeowners, and no checked quotes are counted yet; the quote check will add a quotes series for each city once ten or more are held.
| City | Standard offer | Premium offer | STC discount | Output a year | Lifetime c/kWh (standard) | $ per watt (standard) |
|---|---|---|---|---|---|---|
| Sydney | $17,105 | $20,436 | Zone 3: 138 STCs, $5,382 | 28,480 kWh | 2.5 c | 0.86 |
| Melbourne | $16,019 | $18,695 | Zone 4: 118 STCs, $4,602 | 26,280 kWh | 2.6 c | 0.80 |
| Brisbane | $17,876 | $21,183 | Zone 3: 138 STCs, $5,382 | 30,660 kWh | 2.5 c | 0.89 |
| Perth | $15,133 | $18,145 | Zone 3: 138 STCs, $5,382 | 32,120 kWh | 2.0 c | 0.76 |
| Adelaide | $17,198 | $20,592 | Zone 3: 138 STCs, $5,382 | 30,660 kWh | 2.4 c | 0.86 |
| Canberra | $17,433 | $21,112 | Zone 3: 138 STCs, $5,382 | 31,400 kWh | 2.4 c | 0.87 |
| Hobart | $20,057 | $23,173 | Zone 4: 118 STCs, $4,602 | 25,560 kWh | 3.3 c | 1.00 |
| Darwin | $28,398 | $34,713 | Zone 2: 153 STCs, $5,967 | 32,120 kWh | 3.8 c | 1.42 |
Perth is the cheapest capital for 20 kW at $15,133 and Darwin the dearest at $28,398 on the standard offer. Output a year is 20 kW times each capital's Bureau of Meteorology yield; the lifetime figure divides the standard offer by 25 years of output at 0.5 per cent a year degradation.
What a 20 kW system is
A 20 kW system is 46 panels at 440 W, an inverter of at least 15.04 kW and a three-phase supply without exception. The national $18,659 to $22,254 is derived from the Solar Choice residential 10 kW offer scaled with the commercial index ratio between 10 kW and 30 kW.
Twenty kilowatts sits on the residential to commercial boundary: the Solar Choice commercial index puts systems under 30 kW at about $1,011 per kW after STCs, against $933 per kW on the residential derivation, and the tariff the site pays decides which model applies.
STCs still apply up to 100 kW, and from 1 October 2026 the scheme also covers mid-scale systems to 1 MW with a fixed five-year deeming period, per the CER; LGCs are created only by systems above 1 MW from the same date, so they do not apply at 20 kW.
STC audit for 20 kW by zone
Certificates are kilowatts times the zone factor times the deeming years, rounded down, and valued here at $39 each. Compare the row for your zone with the STC line on the quote: a line 10 per cent or more below it means the installer is pricing certificates under the market and recovering the gap elsewhere. Deeming falls from 5 to 4 years on 1 January 2027.
| Zone (factor) | kW x factor x years | Certificates | Value in 2026 | From 1 January 2027 |
|---|---|---|---|---|
| Zone 1 (1.622) | 20 x 1.622 x 5 = 162.20 | 162 | $6,318 | 129 STCs, $5,031 |
| Zone 2 (1.536) | 20 x 1.536 x 5 = 153.60 | 153 | $5,967 | 122 STCs, $4,758 |
| Zone 3 (1.382) | 20 x 1.382 x 5 = 138.20 | 138 | $5,382 | 110 STCs, $4,290 |
| Zone 4 (1.185) | 20 x 1.185 x 5 = 118.50 | 118 | $4,602 | 94 STCs, $3,666 |
Network limits that decide whether 20 kW connects
Each capital's distributor publishes the inverter and export limits for a basic connection; the figures below were read on 27 October 2026 and "not published" means the page could not be fetched or carries no figure. A 20 kW array needs an inverter of at least 15.04 kW under the 133 per cent rule, so read the single-phase inverter column first.
| City | Distributor | Single-phase inverter | Single-phase export | Three-phase inverter | Three-phase export | Flexible export |
|---|---|---|---|---|---|---|
| Sydney | Ausgrid | 30 | 10 | 30 | 30 | yes, to 10 kW |
| Melbourne | CitiPower | not published | not published | 30 | not published | yes, to 10 kW |
| Brisbane | Energex | 10 | 5 | 30 | 15 | yes, to 10 kW |
| Perth | Western Power | 30 | 5 | 30 | 5 | yes |
| Adelaide | SA Power Networks | 10 | 1.5 | 30 | 1.5 | yes, to 10 kW |
| Canberra | Evoenergy | 10 | 5 | 30 | 10 | not published |
| Hobart | TasNetworks | 10 | 10 | 30 | 30 | not published |
| Darwin | Power and Water | 10 | 5 | 30 | 7 | not published |
20 kW by city
Twenty city pages carry the 20 kW price, the STC audit, the network rules and the output for each location; regional cities without a Solar Choice index show their state capital's figures and say so.
Other system sizes
National standard and premium offers for the other five sizes, October 2026.
To get quotes, start at Solar Scorecard; to test a quote you already hold, use the quote check.
20 kW solar system questions
How much does a 20kW solar system cost in Australia?
$18,659 to $22,254 nationally after STCs in October 2026, the Solar Choice standard and premium installer offers, with Perth cheapest at $15,133 and Darwin dearest at $28,398 on the standard offer.
How many panels is a 20kW system?
46 panels at 440 W each, which gives 20.24 kW of panels; installers quoting a different wattage will quote a different count for the same 20 kW.
How many STCs does a 20kW system get?
138 certificates in Zone 3 (Sydney, Brisbane, Perth, Adelaide), 118 in Zone 4 (Melbourne, Hobart, Canberra) and 162 in Zone 1 (Darwin), worth $5,382, $4,602 and $6,318 at $39 each.
How much power does a 20kW system produce?
25,560 to 32,120 kWh a year across the capitals, from Hobart to Perth, using each city's Bureau of Meteorology yield.
Do STCs apply to a 20kW solar system?
100 kW is the small-scale limit, so a 20 kW array earns STCs in full; from 1 October 2026 mid-scale systems from 100 kW to 1 MW also earn STCs with a fixed five-year deeming period, and LGCs apply only above 1 MW.