Choosing the right solar power setup is one of the most important decisions for Australian homeowners in 2026. When comparing a 5kW and a 6.6kW solar system, the latter has become the gold standard for residential energy efficiency and value. While a 5kW solar system may cost slightly less initially, the long-term benefits of a 6.6kW system often outweigh the savings.
This guide will help you understand which system size fits your lifestyle and budget, ensuring you maximise your investment in renewable energy.
Why system size matters in 2026
Solar technology has advanced rapidly, and the way we use power in Australia has changed. With more people working from home and the rise of electric vehicles, energy demands are higher than ever. Choosing between a 5kW vs 6.6kW solar system is not just about the number of panels; it is about “oversizing.”
Oversizing involves installing panels with a capacity greater than your inverter’s rating. For instance, pairing 6.6kw solar system panels with a 5kW inverter is a common and highly efficient practice. This setup ensures your inverter runs at its peak capacity for more hours each day, especially during morning and afternoon periods.
The rise of the 6.6kW standard
A few years ago, a 5kW system was the go-to choice for the average family. Today, the 6.6 kW solar system leads because it offers the best “bang for your buck.” Most electricity networks in Australia allow a 5kW inverter to be connected without complex approvals. By pushing the panel capacity to 6.6kW, you stay within regulations while generating significantly more electricity.
Comparing the 5kW and 6.6kW solar systems
Understanding the technical and financial differences is key to making an informed choice. Below is a breakdown of how these two popular sizes compare in the current Australian market.
| Feature | 5kW Solar System | 6.6kW Solar System |
| Ideal household size | 2–3 people | 3–5 people |
| Panels required (avg) | 12 | 15 |
| Daily output | 18–22 kWh | 24–28 kWh |
| Annual output | 6,500–8,000 kWh | 8,500–10,000 kWh |
| Roof space | 25–30m² | 30–38m² |
| Typical inverter | 5kW | 5kW |
| Estimated cost (after STCs) | $4,500–$7,000 | $5,000–$8,500 |
| Best for | Lower usage homes | Growing families |
1. Energy generation capacity
The primary difference lies in the daily energy yield. A 5kW system typically produces enough power for a small household or a couple. However, a 6.6kW solar system provides the extra “buffer” needed for larger appliances or future additions to solar battery storage.
Use Energy Matters’ easy-to-use solar power and battery storage calculator to determine the size of your solar system with storage! Our solar calculator will generate performance information and potential savings.
We can send this information to 3 of our pre-vetted and trusted local installers in your area to receive obligation-free solar quotes and take the first step towards true energy independence!
2. The power of oversizing
As mentioned, a 6.6kw solar system often uses a 5kW inverter. This is because solar panels rarely produce their maximum rated power due to heat, dust, or clouds. By having 6.6kW of panels, you ensure that the 5kW inverter is actually hitting its 5kW limit more often, providing you with more usable AC power.
3. Cost vs. return on investment
The 5kW solar system costs less upfront, but the price gap between 5kW and 6.6kW has narrowed. Often, adding those extra panels only costs a few hundred dollars more because the installation and inverter costs remain largely the same. This makes the 6.6kw solar system a more cost-effective choice per watt.
5kW solar system: Is it still relevant?
A 5kW system remains a solid choice for specific types of homeowners. If you have limited roof space or a very low daily electricity consumption (less than 15kWh), this size might be perfect.
- Best for: Retirees, small units, or households with minimal daytime energy use.
- Pros: Lower entry price, smaller roof footprint.
- Cons: Less effective if you decide to add a battery later; may not cover peak summer cooling loads.
While the 5kw solar system cost is attractive, many homeowners find they “outgrow” it quickly as their needs change. If you plan to buy an electric vehicle (EV) or add air conditioning in the future, 5kW may leave you wanting more.
Powering up your EV with solar
If you’re thinking of buying an EV, adding an EV charger to your solar system is a smart way to “fuel” your car with clean, renewable energy.
6.6kW solar system: The Australian favourite
The 6.6kw solar system is currently the most popular residential size in Australia. It strikes the perfect balance between price, performance, and government incentives and rebates.
Maximising government rebates (STCs)
The Australian Government’s Small-scale Renewable Energy Scheme (SRES) provides “rebates” in the form of Small-scale Technology Certificates (STCs). Because these are based on the total kW capacity of the panels, a 6.6kw solar system attracts more certificates than a 5kW system. This higher subsidy helps offset the cost of the extra panels, making the upgrade nearly irresistible.
Battery ready for the future
With the “Cheaper Home Batteries Program” active in 2026, many Australians are looking to store their excess energy. A 6.6kw solar system generates enough surplus power during the day to charge a 10kWh battery. A 5kW system often struggles to fully charge a battery while simultaneously powering the home.
Quick decision checklist
Use this simple checklist:
Choose a 5kW solar system if:
- Small household
- Low power bills
- Limited roof area
Choose a 6.6kW solar system if:
- Medium to large household
- High daytime usage
- Want maximum savings
- Planning EV or battery
Final verdict: 5kW vs 6.6kW solar system
The decision between a 5kW and a 6.6kW solar systemcomes down to energy use and future plans. For most Australian households, the 6.6kW solar system offers better value and faster payback. However, a 5kW solar system remains ideal for smaller homes with lower usage.
Ready to switch to solar? Contact Energy Matters today to let our solar energy experts design the perfect system for you.
Why choose Energy Matters?
Energy Matters has helped thousands of Australians install solar systems. We provide:
- Tier 1 solar panels
- Trusted inverters
- Competitive pricing
- Expert installers
- Ongoing support
Whether you choose a 5kW or 6.6kW solar system, our team will design the perfect system for your home.
- Get a free solar quote today with Energy Matters.
- Compare 5kW vs 6.6kW solar system options now.
- Start saving on your power bills in 2026.
