Solar ROI Calculator
Calculate the payback period and 25-year return on investment for rooftop solar in Queensland.
Your Details
$
6.6kW
3kW15kW
40%
30%80%
How much solar do you use yourself? Higher if home during the day.
$/kWh
Check your bill for your actual rate
$/kWh
Payback Period
3.1 yrs
Annual Savings
$1,597
25-Year Net Benefit
$44,769
Monthly Bill Post-Solar
$17
estimated
Cumulative Savings vs System Cost
The Maths
| Daily generation | 29.2 kWh |
| Annual generation | 10,648 kWh |
| Self-consumed value | $1,278/yr |
| Export value | $319/yr |
| System cost (before STCs) | $6,600 |
| STC rebate (42 STCs) | -$1,638 |
| Net system cost | $4,962 |
What this means
Great result. A 6.6kW system in Queensland should pay for itself in about 3.1 years, then deliver free electricity for another 22+ years. Over 25 years, you're looking at a net benefit of $44,769.
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Frequently Asked Questions
How long do solar panels last?
Most quality solar panels come with a 25-year performance warranty and can last 30+ years. Inverters typically last 10-15 years and may need replacing once during the panel lifespan. Factor in one inverter replacement (~$1,500-$2,500) for a more complete long-term picture.
What size solar system do I need?
A typical Australian household uses 15-25 kWh per day. A 6.6kW system generates roughly 20-30 kWh/day depending on your state and roof orientation. If you have an EV or heat pump, consider going larger (8-10kW+). The best approach is to match your system size to your actual usage from your electricity bill.
Is solar still worth it with low feed-in tariffs?
Absolutely — the key is self-consumption. Every kWh you use from your panels saves you the full retail electricity rate (30-42c/kWh), not the feed-in rate (5-9c/kWh). A system with high self-consumption can pay back in 3-5 years even with low feed-in tariffs. Batteries and smart timing of appliances help maximise self-consumption.
What about shading?
Even partial shading can significantly reduce output. If you have shading issues, micro-inverters or power optimisers can help by allowing each panel to operate independently. A good installer will assess shading with tools like a Solar Pathfinder and design around it. This calculator assumes unshaded panels — reduce your expected output if shading is present.