| Panel count (typical) | 45 panels at ~440 W each |
| Inverter | 15 kW |
| Typical retail price | $19,000–$26,000 |
| Annual generation | ~29,000 kWh / yr |
| Daily generation | ~79 kWh / day |
| Roof area needed | About 100 m² of north-facing roof |
| Suits | Very large homes, dual occupancies and small business premises, $1,400+ / quarter |
| Typical payback | 3.5–5 years |
Federal STC rebate on a 20 kW system, by state
The federal STC rebate scales with system size and STC zone. Here's what a 20 kW install attracts in each state in 2026:
| State | STC zone | Federal STC rebate | Net price (low end) |
|---|---|---|---|
| New South Wales | Zone 3 | $5,506 | $13,494 |
| Victoria | Zone 4 | $4,708 | $14,292 |
| Queensland | Zone 3 | $5,506 | $13,494 |
| South Australia | Zone 3 | $5,506 | $13,494 |
| Western Australia | Zone 3 | $5,506 | $13,494 |
| Tasmania | Zone 4 | $4,708 | $14,292 |
| Australian Capital Territory | Zone 3 | $5,506 | $13,494 |
| Northern Territory | Zone 2 | $6,105 | $12,895 |
Add state-specific rebates on top where applicable. The ACT and NSW stacks typically reduce net cost another $1,600–$2,500.
How a 20 kW system performs day-to-day
On a clear summer day in Sydney or Brisbane, a 20 kW system produces around 107 kWh. On an overcast winter day in Melbourne, it might produce 40 kWh. Annual average is about 79 kWh per day.
For most homes, around 30–40% of that generation is consumed at home in real time. The rest is exported to the grid (and earns the feed-in tariff). Adding a battery typically pushes self-consumption to 80–90%.
Who a 20 kW system actually suits
We get this question on every specialist follow-up. Quick rule of thumb based on quarterly bill size:
- 5 kW , Under $300 / quarter · 1–2 people
- 6 kW , $250–$500 / quarter · 2–4 people
- 6.6 kW , $300–$600 / quarter · 3–4 people
- 8 kW , $500–$800 / quarter · 4–5 people
- 10 kW , $700–$1,000 / quarter · 4–6 people
- 13.2 kW , $900+ / quarter · Large families, all-electric homes, or EV households
- 15 kW , $1,000+ / quarter · All-electric homes, usually three-phase
- 20 kW , $1,400+ / quarter · Very large homes, dual occupancies and small business premises
These are starting points. Other factors that bump you up or down: daytime usage (pool, EV, electric hot water), planned future loads (EV in the next 2 years pushes you up a size), shading, and roof orientation.
20 kW solar system with a battery: the price
Two rebates stack on a solar-plus-battery install and both are applied at the point of sale: the federal STC rebate on the panels, and the Cheaper Home Batteries rebate on the storage. Below is a 20 kW array with each of the two capacities households most often add, priced in STC zone 3.
| Battery | Installed together | Federal STC | Battery rebate | After both |
|---|---|---|---|---|
| No battery | $19,000–$26,000 | −$5,506 | — | $13,494–$20,494 |
| + 10 kWh | $26,000–$39,500 | −$5,506 | −$2,713 | ~$21,031 |
| + 13.5 kWh | $26,800–$40,500 | −$5,506 | −$3,631 | ~$21,013 |
Battery installed prices verified 13 July 2026; the battery rebate is computed from the current Clean Energy Regulator factor of about $271 per usable kWh on the first 14 kWh. "After both" applies the two rebates to the low end of the solar range plus the midpoint of the battery range. NSW and WA add a state battery incentive on top of this; the full breakdown by capacity is on solar battery prices.
A 20 kW system pairs naturally with a 30 kWh battery: big enough to soak up the daytime surplus this array produces, small enough that it still fills most days through winter. Past 14 kWh the federal rebate only pays on 60% of each extra kWh, so the net cost per kWh starts climbing.
One timing note: the battery rebate factor drops on 1 January 2027, which takes about $439 off the 10 kWh figure above. Certificates are earned when the install is certified, not when you sign. The Cheaper Home Batteries explainer has the full schedule, and the rebate calculator gives the figure for your postcode.
Common questions about 20 kW solar
How much does a 20 kW solar system cost in 2026?
Fully installed, a 20 kW system costs between $19,000 and $26,000 retail before rebates. After the federal STC rebate, which is $5,506 in STC zone 3 (Sydney, Brisbane, Perth, Adelaide) and less in the southern zones, most households pay roughly $13,494 to $20,494 net.
How much electricity does a 20 kW solar system generate?
A 20 kW system generates roughly 29,000 kWh per year on average in Australia, that's about 79 kWh per day. Output varies ±20% depending on location, roof orientation, and shading.
Who is a 20 kW system suitable for?
Very large homes, dual occupancies and small business premises households with quarterly bills in the $1,400+ / quarter range. You need roughly About 100 m² of north-facing roof. The point where residential and small-commercial pricing meet. Still claims STCs under the small-scale scheme (the cut-off is 100 kW), but expect a three-phase inverter, a switchboard upgrade and a formal DNSP export agreement.
What inverter pairs with a 20 kW solar system?
A 15 kW inverter is the standard pairing. The "oversized DC" approach (panels rated higher than the inverter) is legitimate, it captures more STC rebate (which is calculated on panel capacity) without significant real-world clipping.
How much does a 20 kW solar system with a battery cost?
$26,000–$39,500 installed for the 20 kW array plus a 10 kWh battery, before rebates. The federal STC rebate ($5,506 in STC zone 3) and the Cheaper Home Batteries rebate ($2,713 on 10 kWh) together take $8,219 off at the point of sale, leaving roughly $21,031 out of pocket. Prices verified 13 July 2026.
Should I add a battery to a 20 kW system?
A 30 kWh battery is the natural pairing for a 20 kW system. The federal Cheaper Home Batteries Program pays about $271 per usable kWh on the first 14 kWh (tapered above), knocking roughly $6,145 off the battery price. Whether it pays depends on how much of your power you use after dark: if the house is empty every evening, the panels alone will pay back faster.
Get matched with a 20 kW installer
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