Check your rebate eligibility
What 20kW Means in Practice
A 20kW solar system generates approximately 70 to 94 kWh per day on average across Australia, with the higher end in Queensland and the NT and the lower end in Tasmania and Victoria. This output is well beyond what a typical household can self-consume, which is why 20kW installations are almost always commercial or large-farm applications rather than purely residential.
The commercial sweet spot for 20kW solar is a business that operates during daylight hours and uses a significant amount of electricity in its daily operations. A medical centre running air conditioning, lighting, sterilisation equipment, and multiple consulting rooms; a childcare centre with constant climate control and kitchen operation; a small manufacturing facility with machinery and compressed air — these are the kinds of businesses where 20kW solar delivers fast, predictable returns.
State-by-State Pricing
| State | After STC rebate | STC rebate (approx.) | Daily output (avg) |
|---|---|---|---|
| Queensland | $18,000–$26,000 | ~$10,000 | 78–94 kWh |
| South Australia | $19,000–$27,000 | ~$9,500 | 76–90 kWh |
| Western Australia | $19,000–$27,000 | ~$10,000 | 78–94 kWh |
| New South Wales | $20,000–$28,000 | ~$9,000 | 72–86 kWh |
| Victoria | $21,000–$29,000 | ~$8,500 | 70–82 kWh |
| Northern Territory | $20,000–$30,000 | ~$11,000 | 84–100 kWh |
Adding Battery Storage to a 20kW System
For businesses that operate during daylight hours only, battery storage often has limited value — the goal is to consume as much solar as possible during operating hours, and there may be little surplus left over for evening use when the premises is closed.
Battery storage makes more sense for businesses with evening operations, security lighting, refrigeration that runs overnight, or premises with a high overnight base load. For these scenarios, a 20kWh to 30kWh commercial battery paired with two 10kW hybrid inverters is a common configuration. After the federal Cheaper Home Batteries Program rebate (which also applies to business installations), the effective battery cost is reduced by approximately 30%.
Commercial battery installations should also consider demand management: some commercial tariffs have demand charges based on peak 15-minute or 30-minute consumption. A battery can shave demand peaks, reducing demand charges on top of the direct energy savings.
Tax Treatment for Business Owners
Business-owned solar systems are depreciating assets for tax purposes. Under the Australian Taxation Office's rules, solar panels and inverters installed for business use are plant and equipment (Division 40) and can be depreciated over their effective life. The current ATO effective life for solar panels is 20 years.
For eligible small businesses, the Instant Asset Write-Off rules may allow the full cost to be deducted in the year of installation rather than spread over the asset's life. The relevant threshold and business turnover limits have changed in recent years, so confirming current eligibility with your accountant before installation is important. The instant asset write-off for solar can substantially improve the net first-year cost in year one.
The next step
If you have any questions about the information in this guide, feel free to get in touch:
Email: hello@whysolar.com.au
Tel: +61 433 405 530
If you're considering solar panels or batteries for your home, Bec and the team can help you get quotes from trusted, pre-vetted local installers:
Written by
Bec RamirezAussie Mum & Energy Expert
Helping families navigate the switch to solar with practical, real-world advice. Bec focuses on the financial side — rebates, bill savings, and financing options — so everyday Australians can see real value from going solar.
Learn more about Bec Ramirez