Choosing the right solar panel system size is one of the most important decisions you'll make. Too small and you'll miss out on potential savings. Too large and you'll pay more upfront for diminishing returns. In Australia, the three most popular residential sizes are 6.6kW, 10kW, and 13kW. Here's how to pick the right one for your home.
System Size Comparison at a Glance
The following table compares the three most common residential solar system sizes across key metrics:
| Metric | 6.6kW | 10kW | 13kW |
|---|---|---|---|
| Typical Cost (after STCs) | $5,500–$8,000 | $8,000–$12,000 | $10,500–$15,000 |
| Daily Output (avg) | 22–28 kWh | 35–42 kWh | 45–55 kWh |
| Annual Output | 8,500–10,500 kWh | 13,000–16,000 kWh | 17,000–20,000 kWh |
| Annual Savings | $1,200–$1,800 | $1,800–$2,500 | $2,000–$3,000 |
| Payback Period | 3–4.5 years | 3.5–5 years | 4–5.5 years |
| Roof Space Needed | ~30 m² | ~45 m² | ~58 m² |
| Number of Panels | 15–16 panels | 22–24 panels | 29–31 panels |
When a 6.6kW System Makes Sense
The 6.6kW system remains Australia's most popular choice, and for good reason. It's the best fit when:
- Your household uses 15–25 kWh per day
- You have 1–3 people at home
- You don't have an electric vehicle or pool
- Your roof space is limited (you only need about 30 m²)
- You want the fastest payback period
- Your budget is under $8,000
For a typical Australian household with moderate energy usage, a 6.6kW system will cover 70–100% of daytime electricity needs and provide a healthy amount of export income.
When to Go Bigger: The 10kW System
A 10kW system generates roughly 50% more power than a 6.6kW system but doesn't cost 50% more, making it excellent value. Consider 10kW when:
- Your household uses 25–40 kWh per day
- You have 3–5 people at home
- You run a pool pump, ducted air conditioning, or a hot tub
- You're planning to add an electric vehicle
- You work from home and have high daytime usage
- You plan to add a battery in the future
The 10kW system requires a larger inverter (typically 8–10kW), which adds to the cost, but the extra generation capacity more than compensates over the system's lifetime.
Going Big: The 13kW System
A 13kW system is the largest commonly available for single-phase residential connections. It's worth considering when:
- Your household uses 35+ kWh per day
- You have a large family (5+ people)
- You have an electric vehicle that charges at home
- You have a pool with an electric heater or heat pump
- You run a home business with significant energy needs
- You're pairing with a large battery (10kWh+)
- You have three-phase power (allowing higher export limits)
The Diminishing Returns of Oversizing
There's a common misconception that bigger is always better with solar. While larger systems produce more energy, the financial returns don't scale linearly. Here's why:
- Export limits: Your network may cap how much you can send back to the grid, meaning excess generation is lost.
- Low feed-in tariffs: Extra energy exported at 5–7c/kWh provides a much lower return than energy self-consumed at 30c+/kWh.
- Longer payback: The incremental cost of going from 10kW to 13kW may take longer to recoup than the initial 6.6kW investment.
- Inverter clipping: If your inverter is smaller than your panel array, it will clip output during peak generation times.
The sweet spot is sizing your system to match your daytime consumption plus a reasonable buffer for export and future growth.
Roof Space Considerations
Modern solar panels (around 420–440W each) measure approximately 1.7m x 1.1m. You'll need roughly 2 m² per panel, including spacing. North-facing roof space is ideal, but east and west-facing panels can still produce 80–85% of the output of north-facing ones — see our detailed west-facing vs north-facing solar comparison for how this affects self-consumption on a time-of-use tariff. Some key considerations:
- Shading from trees, chimneys, or neighbouring buildings can significantly reduce output
- Split arrays across multiple roof faces are common and work well with microinverters or optimisers
- Flat roofs work but require tilt frames that add cost and spacing requirements
- Heritage overlays or body corporate rules may restrict panel placement
Find Your Ideal System Size
The right system size depends on your specific energy usage, roof space, budget, and future plans. Use our Solar ROI Calculator to model different system sizes with your actual electricity rate, usage pattern, and location. You can compare how a 6.6kW, 10kW, or 13kW system would perform for your household.