Check your rebate eligibility
Where 15kW Sits in the Market
A 15kW solar system is not for the average Australian household. The standard 6.6kW system covers most 3 to 4 person homes. A 10kW system handles larger homes with higher consumption. At 15kW, you are in the territory of very large residential properties or small commercial premises.
The residential use cases that justify 15kW are specific: two electric vehicles both needing daily charging, a large swimming pool with an electric heating pump, a home with 6 or more people and high consumption, or a property running a home-based business with significant equipment. Without at least one of these high-load scenarios, a 13kW system usually delivers better value for a residential property.
State-by-State Pricing
| State | After STC rebate | STC rebate (approx.) | Daily output (avg) |
|---|---|---|---|
| Queensland | $13,000–$19,000 | ~$7,500 | 58–70 kWh |
| South Australia | $13,500–$19,500 | ~$7,000 | 56–68 kWh |
| Western Australia | $13,500–$19,500 | ~$7,500 | 58–70 kWh |
| New South Wales | $14,000–$20,000 | ~$6,800 | 54–64 kWh |
| Victoria | $14,500–$21,000 | ~$6,500 | 52–62 kWh |
| Tasmania | $16,000–$22,000 | ~$5,500 | 44–54 kWh |
Three-Phase Power: What You Need to Know
A 15kW installation almost always requires three-phase power. Network operators classify connections of this size as requiring three-phase supply for balanced load distribution. If your property currently has single-phase power, you will need to arrange a three-phase upgrade from your local network operator before installation.
Three-phase upgrade costs typically range from $3,000 to $8,000 depending on the distance from the street, the complexity of the meter board upgrade, and your network operator. In areas with good grid infrastructure, the cost can be at the lower end. In rural areas or properties with older wiring, it may be higher. Get this quote before committing to a 15kW system, as it can significantly affect total project cost.
The benefit of three-phase power is not just for solar — it also supports larger EV chargers (phase 2 charging at 11kW or 22kW), larger air conditioning systems, and better power quality for sensitive equipment.
Comparing 13kW vs 15kW
| Factor | 13kW | 15kW |
|---|---|---|
| Three-phase needed? | Not always (dual single-phase option) | Usually yes |
| Typical cost after rebate | $9,000–$16,000 | $13,000–$22,000 |
| Daily output (east coast avg) | 44–58 kWh | 52–70 kWh |
| Best for | Large home, 1 EV, high usage | Very large home, 2 EVs, small business |
For most large residential properties, a 13kW system is the practical ceiling before the complexity and cost of three-phase upgrades make sense. If you already have three-phase power and high consumption, 15kW is a natural choice. If upgrading to three-phase is part of a broader electrification plan (including fast EV charging), building in 15kW solar capacity at that point makes financial sense.
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