A 20kW solar system costs roughly A$17,600 to A$19,000 fully installed in Australia as at November 2026, after the federal STC discount and including GST. That is a Solar Cobber estimate, not a published quote: no price index publishes a 20 kW average, so we applied Solar Choice’s A$0.88 to A$0.95 per watt national range. Expect about 46 panels, 92 square metres of roof, a three phase connection and 138 STCs in most capitals.
This guide also covers 15kW and 30kW systems. It is independent desk research: Solar Cobber did not request quotes, and no installer paid to be mentioned.
Source: Solar Choice Price Index, 1 November 2026; Clean Energy Regulator, page updated 29 October 2026.
Key facts
- The Solar Choice Price Index for November 2026 states a national average installed price of A$0.88 to A$0.95 per watt including GST and the STC discount, but it publishes prices only up to 10 kW.
- Applying that range, a 15kW solar system costs about A$13,200 to A$14,250, a 20kW solar system A$17,600 to A$19,000 and a 30kW solar system A$26,400 to A$28,500 (Solar Cobber calculation, November 2026).
- A 20kW solar system installed in 2026 in Sydney, Brisbane, Perth, Adelaide or Canberra earns 138 small-scale technology certificates (STCs), worth about A$5,500 at A$39.85 each.
- From 1 January 2027 the same 20kW solar system earns 110 STCs, about A$1,100 less, because the Clean Energy Regulator cuts the deeming period from 5 years to 4.
- A 20kW solar system needs about 46 panels of 440 W (20.24 kW) and roughly 92 square metres of roof at 2 square metres a panel, allowing for gaps.
- Clean Energy Council guide figures (2011 and 2013 editions) put a 20kW solar system at 72 kWh a day in Melbourne, 78 in Sydney and 88 in Perth, averaged over a year.
- Small-scale STCs apply to solar systems up to 100 kW, so 15kW, 20kW and 30kW systems all qualify.
20kW solar system price (November 2026)
A 20kW solar system costs about A$17,600 to A$19,000 installed, which is A$0.88 to A$0.95 per watt. Solar Choice’s Price Index, dated 1 November 2026, publishes 3, 4, 5, 6, 7 and 10 kW prices only, so for larger sizes the table below is our extension of its per-watt range, not a quote.
The chart shows the part Solar Choice does publish: the national average price per watt falls as systems get bigger, from A$1.37 at 3 kW to A$0.98 at 10 kW.
Source: Solar Choice Price Index, 1 November 2026 (checked 14 November 2026). Solar Cobber calculation: Solar Choice national price (A$4,120, 4,880, 5,560, 6,350, 7,080, 9,830) divided by watts.
View the data as a table
| A$ per watt | |
|---|---|
| 3 kW | A$1.37 |
| 4 kW | A$1.22 |
| 5 kW | A$1.11 |
| 6 kW | A$1.06 |
| 7 kW | A$1.01 |
| 10 kW | A$0.98 |
Price per watt keeps falling with size up to 10 kW, but the curve flattens, so we use the lower and upper ends of Solar Choice’s own 2026 range for larger systems.
| System size | Installed price, low (A$0.88 per W) | Installed price, high (A$0.95 per W) | Basis |
|---|---|---|---|
| 10 kW | A$8,810 | A$9,500 | Solar Choice national average A$9,830; SolarQuotes about A$9,000 to A$12,000 (12 October 2026) |
| 13 kW | A$11,440 | A$12,350 | SolarQuotes publishes A$11,000 to A$16,000 for 13 kW |
| 15 kW | A$13,200 | A$14,250 | Solar Cobber calculation |
| 20 kW | A$17,600 | A$19,000 | Solar Cobber calculation |
| 30 kW | A$26,400 | A$28,500 | Solar Cobber calculation |
- Low (A$0.88 per W)
- High (A$0.95 per W)
Source: Solar Choice national per-watt range, November 2026; extension to larger sizes is a Solar Cobber calculation. Estimate, not a quote. Solar Choice does not publish averages above 10 kW.
View the data as a table
| Low (A$0.88 per W) | High (A$0.95 per W) | |
|---|---|---|
| 15 kW | A$13,200 | A$14,250 |
| 20 kW | A$17,600 | A$19,000 |
| 30 kW | A$26,400 | A$28,500 |
A 20kW solar system is an estimated A$17,600 to A$19,000 and a 30kW system about A$26,400 to A$28,500; real quotes will vary with brand, roof and network work.
Prices above 10 kW are not widely published. Quotes for the same 20 kW can differ by thousands because three phase inverters, extra roof structure, network applications and mid-range versus premium panels all sit outside a per-watt average. Treat the range as a sanity check for quotes, and compare real ones using our guide to comparing solar quotes. Compare with the 10kW and 13kW guides.
What changes the price of a 20kW solar system
Phase, inverter choice and roof access move a 20kW solar system price most. Hardware is the smaller part: Solar Choice puts mainstream 440 W panels at A$80 to A$150 each and premium panels at A$250 or more, so 46 panels range from about A$3,700 to A$6,900 at the mainstream end and far more for premium brands.
- Three phase inverter or several inverters. At this size most networks require a three phase connection (see below). Three phase inverters cost more per kW than single phase.
- Panel tier. See our reviews of the Trina Vertex S+, Aiko Neostar, Jinko Tiger Neo, REC Alpha Pure-RX and LONGi Hi-MO X6.
- Roof, switchboard and access. Tin, tile and flat roofs, scaffolding and switchboard upgrades change labour.
- Location. In November 2026 Solar Choice’s 10 kW average ran from A$8,410 in Perth to A$11,080 in Hobart and A$14,930 in Darwin, so remote and northern locations cost more per watt.
How the STC discount applies to 15kW, 20kW and 30kW systems
A 20kW solar system installed in 2026 earns 138 STCs in zone 3 and 118 in zone 4. A small-scale technology certificate (STC) is a tradable certificate created under the federal Small-scale Renewable Energy Scheme; you assign it to your installer for an upfront discount. The Clean Energy Regulator’s formula is system size (kW) multiplied by the postcode zone rating multiplied by the deeming period (5 years in 2026, 4 in 2027); it covers systems up to 100 kW.
The working for a 20kW system in Sydney, Brisbane, Perth, Adelaide or Canberra (zone 3, rating 1.382 MWh per kW per year) is 20 x 1.382 x 5 = 138.2, rounded down to 138. We round down, as our other guides do; confirm the whole-number rule with the Clean Energy Regulator calculator before relying on an exact count.
| System size | Zone 3, 2026 (5 years) | Zone 3, 2027 (4 years) | Zone 4 (Melbourne, Hobart), 2026 | Zone 4, 2027 | Zone 2 (Darwin), 2026 |
|---|---|---|---|---|---|
| 15 kW | 103 | 82 | 88 | 71 | 115 |
| 20 kW | 138 | 110 | 118 | 94 | 153 |
| 30 kW | 207 | 165 | 177 | 142 | 230 |
Zone ratings come from the Clean Energy Regulator’s postcode zone document (as of 1 January 2020), and zones are by postcode, not city. At about A$39.85, the October 2026 traded price reported by Demand Manager (the Clearing House price is fixed at A$40 excluding GST), a 20kW system in zone 3 gets about A$5,500 off in 2026.
- Installed in 2026 (5 years)
- Installed in 2027 (4 years)
Source: Clean Energy Regulator zone ratings and deeming periods, pages dated 29 October 2026. Solar Cobber calculation: kW x 1.382 x deeming period.
View the data as a table
| Installed in 2026 (5 years) | Installed in 2027 (4 years) | |
|---|---|---|
| 15 kW | 103 | 82 |
| 20 kW | 138 | 110 |
| 30 kW | 207 | 165 |
Waiting until January 2027 removes 21, 28 and 42 STCs from a 15, 20 and 30kW system, about A$840, A$1,100 and A$1,670 at A$39.85. Our STC explainer covers eligibility. Above 100 kW a system moves to the mid-scale scheme, which has a fixed 5 year deeming period.
20kW solar system: how many panels and how much roof?
A 20kW solar system uses about 46 panels of 440 W (20.24 kW), 45 panels of 450 W or 40 panels of 500 W, and needs roughly 92 square metres of roof. Residential panels are commonly 440 to 475 W according to Solar Choice, and datasheet sizes such as the Trina Vertex S+ (1762 x 1134 mm, 2.0 square metres) and Jinko Tiger Neo (1722 x 1134 mm, 1.95 square metres) support about 2 square metres each.
| System | 440 W panels | Panel area (2.0 m2 each) | Typical annual output, zone 3 (kWh) |
|---|---|---|---|
| 15 kW | 34 (14.96 kW) | 68 m2 | 20,730 |
| 20 kW | 46 (20.24 kW) | 92 m2 | 27,640 |
| 30 kW | 68 (29.92 kW) | 136 m2 | 41,460 |
Roof area is for panels only. East-west and flat-roof layouts, tilt frames and walkways need extra space. See solar panel sizes and dimensions and our guide to how many solar panels you need.
How much power does a 20kW solar system produce?
A 20kW solar system produces about 70 to 100 kWh a day averaged across the year, or roughly 24,000 to 30,700 kWh a year in the capitals, depending on location. The table uses Clean Energy Council guide figures. These are old: the figures come from the Council’s 2011 consumer guide (per kW) and 2013 business guide (10 kW row), reproduced by Solar Choice, and we found no newer per-city table. Treat them as a guide to the pattern between cities.
Source: Clean Energy Council, Guide to installing solar PV for business and industry (2013 edition), 10 kW row, hosted by Solar Choice. Solar Cobber calculation: 10 kW figure multiplied by 2.
View the data as a table
| 20 kW system | |
|---|---|
| Alice Springs | 100 kWh |
| Darwin | 88 kWh |
| Perth | 88 kWh |
| Canberra | 86 kWh |
| Adelaide | 84 kWh |
| Brisbane | 84 kWh |
| Sydney | 78 kWh |
| Melbourne | 72 kWh |
| Hobart | 70 kWh |
Perth, Darwin and Canberra lead the capitals at 86 to 88 kWh a day; Hobart and Melbourne trail at 70 and 72.
For comparison, the Clean Energy Regulator’s deemed output for 20 kW is 75.7 kWh a day in zone 3 and 64.9 in zone 4 (zone rating x size / 365, our calculation). It is conservative because it sets the rebate. Scale the chart by 0.75 for 15 kW and 1.5 for 30 kW.
Output also swings by season. The Bureau of Meteorology’s mean daily solar exposure shows Perth’s December at 8.3 kWh per square metre a day against 2.6 in June, and Hobart’s at 6.5 against 1.3.
- Perth
- Sydney
- Melbourne
- Hobart
Source: Bureau of Meteorology climate averages, 1990 to 2026 (checked 14 November 2026). Stations: Perth Metro, Sydney Airport, Melbourne Airport, Hobart Airport West. Solar Cobber calculation: MJ/m2 divided by 3.6.
View the data as a table
| Perth | Sydney | Melbourne | Hobart | |
|---|---|---|---|---|
| Jan | 8.08 | 6.33 | 6.67 | 6.42 |
| Feb | 7.14 | 5.58 | 5.78 | 5.39 |
| Mar | 5.72 | 4.67 | 4.50 | 4.03 |
| Apr | 4.22 | 3.78 | 3.14 | 2.64 |
| May | 3.17 | 2.89 | 2.17 | 1.72 |
| Jun | 2.64 | 2.42 | 1.78 | 1.33 |
| Jul | 2.83 | 2.75 | 2.00 | 1.58 |
| Aug | 3.64 | 3.61 | 2.81 | 2.36 |
| Sep | 4.78 | 4.69 | 3.78 | 3.53 |
| Oct | 6.31 | 5.58 | 4.94 | 4.78 |
| Nov | 7.44 | 6.06 | 5.86 | 5.75 |
| Dec | 8.31 | 6.53 | 6.61 | 6.53 |
Winter exposure in Melbourne and Hobart is about a quarter of summer, so a 20kW system in the south is sized for the annual total, not June.
Three phase, inverter limits and export limits
A 20kW solar system almost always needs three phase power, because most networks cap a single phase home’s solar inverter at 10 kW and allow up to 30 kW on three phase. Our single phase versus three phase guide tabulates each network, and the table below summarises the position we checked in November 2026 from it.
Typical limits are a 10 kW inverter and 5 kW export on single phase, against 30 kW and 15 kW (5 kW per phase) on three phase. Ausgrid, SA Power Networks and TasNetworks offer flexible exports up to 30 kW on three phase, Essential Energy and Western Power cap the whole site at about 5 kW, and Power and Water (NT) allows 7 kW on three phase.
So a 15kW array usually means three phase with a 10 to 15 kW inverter, a 20kW array a 15 to 20 kW three phase inverter, and 30kW the full network allowance. In the Northern Territory, our 10kW guide notes an inverter above 5 kW must be three phase. Above the standard inverter limits an application is assessed individually by the network. We did not verify each network’s threshold for that, so ask your distributor before you buy.
A large array exporting 5 kW to 15 kW still works, because the building uses power first. What you lose is the unused surplus: feed-in tariffs are only a few cents per kWh, and some networks charge for exports (sun tax and export charges, feed-in tariff tracker).
Is a 20kW solar system worth it? A worked payback example
A 20kW solar system at A$18,300 pays back in about 2.7 years if 70 per cent of its output is used on site, 4.2 years at 40 per cent and 6.7 years at 20 per cent, in the stated example. This is a Solar Cobber calculation for a large site with three phase power, not a quote.
Assumptions: price A$18,300 (middle of A$17,600 to A$19,000); output 27,640 kWh a year (20 kW x 1.382 MWh, the Clean Energy Regulator zone 3 deemed output, so conservative); avoided usage rate 33.1 c/kWh and feed-in tariff 4 c/kWh, the Sydney assumptions in our 10kW guide (Default Market Offer 2026-27 and IPART benchmark); no degradation, no export clipping, no maintenance. Business tariffs differ, so use your own bill.
| Self-consumed share | Used on site (kWh) | Exported (kWh) | Annual benefit | Simple payback |
|---|---|---|---|---|
| 70 per cent (daytime business or farm) | 19,348 | 8,292 | A$6,736 | 2.7 years |
| 40 per cent | 11,056 | 16,584 | A$4,323 | 4.2 years |
| 20 per cent (empty home by day) | 5,528 | 22,112 | A$2,714 | 6.7 years |
Source: Solar Cobber calculation; price from Solar Choice per-watt range, rates as in our 10kW guide (AER 2026-27 DMO, IPART). Annual benefit = used kWh x 0.331 + exported kWh x 0.04, divided into A$18,300.
View the data as a table
| Payback (years) | |
|---|---|
| 70% used | 2.7 yrs |
| 40% used | 4.2 yrs |
| 20% used | 6.7 yrs |
The calculation shows that a large system earns its keep through the share used on site: a home that is empty by day waits more than twice as long as a busy workshop. It also assumes the network lets you export; a 5 kW cap clips a lot of the exported kWh in the 20 per cent row. A battery changes the mix: see solar and battery package prices and what a solar battery costs.
Bigger commercial buildings are covered in our guide to commercial solar systems and best commercial solar installers in Australia. A 15kW system suits a large three phase home, and 30kW a small business, farm shed or school.
What to check on your 20kW quote
A sound 20kW quote names the array size, inverter model, phase and approved export limit. Check:
- Panel count, wattage, brand and total kW (for example 46 x 440 W = 20.24 kW).
- Inverter model, size, phase and number of units, and the network’s approved export limit.
- The number of STCs and the price per certificate; match it to the table above for your postcode zone.
- Who applies to the network, and whether approval is already in hand before install.
- Roof structure, access equipment and switchboard work, shown as separate lines.
- Workmanship, panel and inverter warranties, and who honours them if the installer closes (company failures tracker).
- The retailer’s listing on the Clean Energy Council approved retailer list (New Energy Tech Consumer Code) and the installer’s on the Solar Accreditation Australia register. Check both yourself.
Browse solar installers in your state, see the top 10 solar panel installers, and read how to choose a solar installer.
FAQ
How much does a 20kW solar system cost in Australia?
About A$17,600 to A$19,000 installed in November 2026, after STCs and including GST, on our estimate. No price index publishes a 20 kW average, so this applies Solar Choice’s A$0.88 to A$0.95 per watt national range. Quotes vary with brand, roof and network work.
How much does a 15kW solar system cost?
About A$13,200 to A$14,250 installed in November 2026 on the same per-watt basis. That is a Solar Cobber estimate. SolarQuotes publishes A$11,000 to A$16,000 for a 13 kW system, which brackets this range.
How much does a 30kW solar system cost?
About A$26,400 to A$28,500 installed in November 2026, after STCs and GST, on the same per-watt basis. A 30kW system earns 207 STCs in zone 3 in 2026. Quotes at this size should be itemised.
How many panels do I need for a 20kW solar system?
About 46 panels of 440 W gives 20.24 kW. Using 450 W panels you need 45, and with 500 W panels 40. Allow roughly 92 square metres of roof for panels at about 2 square metres each.
How much power does a 20kW solar system produce?
About 70 to 100 kWh a day averaged over the year in the capitals, per Clean Energy Council guide figures, with Sydney at 78 and Perth at 88. The Clean Energy Regulator’s zone 3 deemed output is 27,640 kWh a year, or about 76 kWh a day. Winter output is far lower than summer in the south.
Do I need three phase for a 20kW solar system?
In practice yes. Most networks limit a single phase solar inverter to 10 kW and allow up to 30 kW on three phase, so a 20kW array normally needs three phase power. Check your network’s rule for your address.
What is the export limit for a 20kW solar system?
It depends on the network. Typical limits are 5 kW on single phase and 15 kW on three phase, with Ausgrid, SA Power Networks and TasNetworks offering flexible exports up to 30 kW on three phase. Power and Water in the Northern Territory allows 7 kW on three phase.
Is a 20kW solar system worth it?
It is worth it when much of the output is used on site. In our worked example it pays back in about 2.7 years at 70 per cent self-consumption and 6.7 years at 20 per cent, before network export limits. A home empty by day gets a much smaller return.
Sources
- Solar Choice, solar panel price index (November 2026), checked 14 November 2026.
- SolarQuotes, solar panel cost, updated 12 October 2026.
- Clean Energy Regulator, calculate STC entitlements, updated 29 October 2026, and its postcode zone ratings (as of 1 January 2020).
- Clean Energy Regulator, buy and sell STCs, updated 14 September 2026; Demand Manager Certificate Report, October 2026.
- Clean Energy Council, Guide to installing solar PV for business and industry (2013) and consumer guide (2011), copies hosted by Solar Choice.
- Bureau of Meteorology climate averages for Perth, Sydney, Melbourne and Hobart stations, checked 14 November 2026.
- Panel datasheets from Trina Solar and Jinko Solar, as summarised in our product reviews.
About this guide
This guide was written by the Solar Cobber editorial team from independent desk research checked in November 2026. Prices for 15kW, 20kW and 30kW systems are our calculations from a published per-watt range, not quotes. Solar Cobber is a free directory that may earn referral or advertising fees from installers; commercial relationships never affect our content. This is general information, not financial advice. Spotted an error? Tell us at /contact.
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