Solar Panel System Output & Battery ROI Calculator
Estimate solar PV generation, self-consumption savings, feed-in tariff revenue, and payback period.
Last reviewed by the myCalculator Editorial Team
Input Parameters
Standard Australian residential systems are 6.6 kW (with 5 kW inverter)
Perth/Brisbane ~4.8-5.2, Sydney/Adelaide ~4.4-4.6, Melbourne/Hobart ~3.8-4.2
Net out-of-pocket price after Federal STC solar rebates
Percentage of solar energy consumed inside the home during daytime (without battery: 30-50%; with battery: 70-90%)
Calculation Results
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Formula & How Solar Panel System Output & Battery ROI Calculator Works
Annual solar output is the system size multiplied by the peak sun hours, the days in the year and the system efficiency. A 6.6 kW system with 4.5 peak sun hours at 80% overall efficiency produces 6.6 × 4.5 × 365 × 0.8 = about 8,672 kWh a year. If 45% is used at home, that is 3,903 kWh worth $0.32 each, or $1,249, and the remaining 4,770 kWh exported at 6.5 cents earns $310, so the annual benefit is about $1,559. On a net system cost of $5,500 the payback is about 3.5 years. Self-consumption is the biggest lever, which is why batteries and shifting usage to the daytime matter. Actual output varies with orientation, shading and weather.
- Enter Solar Array System Size (kW) (kW): Input your target parameter value.
- Enter Average Daily Peak Sun Hours (hrs/day): Input your target parameter value.
- Enter Net Installed System Cost ($ AUD) ($): Input your target parameter value.
- Enter Grid Electricity Tariff (¢/kWh) (¢/kWh): Input your target parameter value.
- Enter Solar Feed-in Tariff FiT (¢/kWh) (¢/kWh): Input your target parameter value.
- Enter Solar Self-Consumption Rate (%) (%): Input your target parameter value.
- Apply Formula: Calculate using
Annual kWh = kW × Sun Hours × 365 × η | Savings = (Self-consumed kWh × Grid Rate) + (Exported kWh × FiT) | Payback = Cost ÷ Annual Savings. - Review Results: View exact computed answers, metrics, and worked mathematical proofs.
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Frequently Asked Questions (FAQs)
How long does a 6.6 kW solar system take to pay for itself in Australia?
In most Australian states, a standard 6.6 kW solar PV system costs between $4,500 and $6,500 after STC rebates and achieves a full return on investment (payback period) within 3.5 to 5.5 years.
How does adding a battery storage system affect solar ROI?
A home battery (e.g. 10–13.5 kWh) increases daytime solar self-consumption from ~45% up to 80–95% by storing afternoon excess for night usage, reducing peak grid import fees.
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Authoritative Standards & Verified Reference Citations
Calculations and mathematical logic on this page are grounded in published statutory rules, regulatory standards, and official government data published by the following bodies:
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Residential mortgage serviceability buffer framework (3.0% stress test hurdle rate).
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