Solar Panel ROI Calculator (Australia)
Free solar panel ROI calculator for Australian homes. Estimate payback, lifetime savings, and IRR using your STC-rebated cost, FiT, and self-consumption rate.
Prepared by the Solar Calculator HQ editorial team. Review our formula, source and limitation standards.
Solar Panel ROI Calculator
Net cost after rebate
$7,800
Payback period
2.6 years
Excellent
Lifetime savings
$108,036
25 years
Lifetime ROI / Equivalent IRR
1285%
11.1% IRR
How to use this calculator
Enter six numbers and the calculator returns net cost (after STC rebate), payback period in years, total lifetime savings, and IRR:
- Installed system cost — gross price quoted by your CEC-accredited installer. Most installers quote post-STC; if you see a pre-STC number, subtract the rebate (typically $300-$500/kW). Typical 2026 prices: $6,500-$8,500 for 6.6 kW.
- Annual production (kWh) — what your system makes year one. CEC Postcode Calculator or your installer’s quote will give this. Sydney 6.6 kW system: 9,500-10,200 kWh/year. Melbourne: 8,800-9,400 kWh/year. Brisbane: 10,500-11,200 kWh/year.
- Electricity rate ($/kWh) — your blended retail rate (look at your bill — total cost / total kWh used). 2026 averages: NSW 32-38 c, VIC 28-32 c, QLD 30-34 c, SA 38-44 c, WA 32-35 c (Synergy A1 tariff).
- Annual rate escalation (%) — historical AER average is 3.6%; 3.5% is a reasonable forward-looking number.
- System lifetime (years) — 25 years matches CEC product warranty for tier-1 panels.
- STC rebate (%) — leave at 0 if your installer already quoted post-STC; enter the percentage if you have a gross quote (typically 30-35% in Zones 2-4).
How the math works
Standard energy-cost-displacement model with rate escalation and 0.5%/year panel degradation:
year_n_savings = annual_kWh × (1 - 0.005)^(n-1) × blended_rate × (1 + escalation)^(n-1)
total_savings = sum of year_n_savings for n = 1 to lifetime
net_cost = system_cost × (1 - rebate%/100)
payback = year where cumulative savings reaches net_cost
ROI% = (total_savings - net_cost) / net_cost × 100Worked example for a Sydney west-facing roof, 6.6 kW system:
- System: 6.6 kW, $7,800 post-STC
- Production year 1: 9,800 kWh
- Blended rate: 21 c/kWh (50% self-consumption at 33 c retail + 50% export at 8 c FiT)
- Year 1 savings: 9,800 × $0.21 = $2,058
- Year 25 savings: 9,800 × 0.995^24 × 0.21 × 1.035^24 ≈ $4,170
- 25-year cumulative: ~$67,500
- Payback: 4.4 years
- ROI: ($67,500 − $7,800) / $7,800 = 765%
- IRR: (67,500/7,800)^(1/25) − 1 ≈ 9.0%/year
Payback by Australian capital city (2026 reference)
Based on CEC Postcode Calculator, BoM solar irradiance, and AER 2025-26 DMO/VDO benchmarks for a 6.6 kW system at $7,800 post-STC, north-facing 22° pitch:
| City | Peak sun hrs | Annual kWh | Avg rate | Year 1 savings | Payback | 25-yr ROI |
|---|---|---|---|---|---|---|
| Darwin | 5.7 | 11,800 | 28 c | $1,650 | 5.3 yrs | 660% |
| Brisbane | 5.2 | 10,800 | 32 c | $2,265 | 4.0 yrs | 845% |
| Perth | 5.3 | 11,000 | 33 c | $2,180 | 4.2 yrs | 800% |
| Sydney | 4.6 | 9,800 | 33 c | $2,058 | 4.4 yrs | 765% |
| Adelaide | 4.9 | 10,400 | 41 c | $2,725 | 3.4 yrs | 1010% |
| Canberra | 4.7 | 9,950 | 30 c | $1,890 | 4.7 yrs | 700% |
| Melbourne | 4.2 | 8,950 | 30 c | $1,700 | 5.2 yrs | 615% |
| Hobart | 3.8 | 8,000 | 32 c | $1,615 | 5.5 yrs | 580% |
(Blended rate assumes 50% self-consumption at retail + 50% export at typical FiT for the state; Adelaide stands out due to AGL DMO base rate 41-44 c/kWh in mid-2026.)
What drives Australian solar ROI
Upward (faster payback)
- High retail rates — SA, NSW Endeavour and Ausgrid networks.
- North-facing roofs at 20-30° — within 5% of optimal annual yield.
- Daytime self-consumption — pool pumps, ducted air-conditioning, EV charging shift load into solar window.
- Time-of-Use retail tariffs — peak rates 4-9 PM weekdays often exceed 50 c/kWh, making battery + EV-charge arbitrage highly valuable.
- Premium FiT enrolment — NSW Solar Bonus and VIC PFiT customers continue to benefit (these schemes close in 2028 and 2024 respectively).
Downward (slower payback)
- East/west or shaded roof — Sydney/Melbourne terraces with chimneys lose 15-25% yield.
- Low daytime usage — empty house weekdays = high export %, low blended rate.
- Capacity-limited grids — parts of SA Power Networks, WA Western Power, Energex have export limits (3-5 kVA per phase) that cap excess production into FiT.
- NEM 3.0-style export tariffs — under proposed AEMC reforms, peak-PV-period exports may be charged or capped.
Compare solar to other Australian investments
Over a 25-year horizon, residential solar’s tax-free IRR of 9-12% beats most accessible alternatives. Returns are not assessable income (ATO confirmed in TR 2003/3 for solar feed-in payments to residential homeowners). The trade-off is illiquidity (sell the house to exit) and concentration risk.
For a typical Sydney household: $7,800 invested at a 9% post-tax IRR over 25 years is equivalent to a 12.7% pre-tax return for a 30%-bracket taxpayer — well ahead of the All Ordinaries long-run 7% real return.
Pair this with the payback calculator and cost calculator
ROI shows the lifetime view; payback pinpoints break-even year; cost helps you compare installer quotes. Always cross-check with the CEC Postcode Calculator before committing.
Sources
- Clean Energy Council Solar Retailer Code of Conduct + Postcode Calculator — installer benchmarks and yield estimator
- Australian Energy Regulator (AER) DMO 2025-26 — default market offer reference rates
- SunWiz Solar Insights Report 2026 — installed cost and rebate trends
- Bureau of Meteorology solar exposure data — peak sun hours by location
- Federal Cheaper Home Batteries Program — 30% battery rebate guidelines
Frequently asked questions
What's a typical solar ROI in Australia in 2026?
Australian residential solar consistently ranks among the world's best ROIs because system costs are low (Clean Energy Council benchmarks: $0.95-$1.15/W after STC rebate) and irradiance is high (4.5-5.5 peak sun hours nationally). A 6.6 kW system costs roughly $6,500-$8,000 post-STC, generates 9,000-10,500 kWh annually, and at typical retail rates of 30-35 c/kWh produces $1,800-$2,500 of year-one savings (50% self-consumed + 50% exported at FiT). Payback runs 4-6 years and lifetime ROI typically exceeds 400%, IRR 12-15%.
How does the STC rebate affect my solar ROI?
STC entitlement depends on rated kW, postcode zone and the deeming period, while the assigned certificate value depends on the contract. In 2026, a 6.6 kW Zone 3 system creates about 45 STCs. At an illustrative A$35-A$40 each, that is roughly A$1,575-A$1,800 before agent fees. Most quotes show the assigned value as an upfront discount; verify the count and price rather than using an old per-kW rule of thumb.
What feed-in tariff (FiT) should I use in my ROI model?
FiTs vary widely by state and retailer. As of April 2026: Victoria minimum FiT 4.9 c/kWh (Essential Services Commission), QLD voluntary 5-9 c/kWh, NSW IPART benchmark 4.9-7.4 c/kWh, SA 4-8 c/kWh, WA DEBS 2.25 c/kWh peak / 10 c/kWh peak time-windows. Some retailers (Amber, AGL Solar Saver) offer wholesale-passthrough or premium FiTs of 8-15 c/kWh. The trend is downward — model new FiTs at 5-8 c/kWh and existing premium FiTs (NSW Solar Bonus 60 c/kWh, VIC PFiT 60 c/kWh) only if you're already enrolled.
Should I add a battery to improve my solar ROI?
In 2026, batteries pencil out for households with high evening consumption + a low FiT. The federal Cheaper Home Batteries Program (launched 1 July 2025) delivers a 30% subsidy on installed battery cost up to 50 kWh — typical 10 kWh battery: ~$10,000 gross → ~$7,000 post-subsidy. Payback runs 7-10 years if you're shifting >5 kWh/day from grid-import (35 c/kWh) to self-consumption. Without the federal rebate, batteries are still 10-12 year payback and rarely improve overall system IRR. Run the [payback calculator](/calculators/solar-panel-payback-calculator/) for both scenarios.
How does electricity rate escalation affect long-term solar value?
AER (Australian Energy Regulator) data shows residential rates rose 3.6% per year on average over the last decade, with sharp spikes in 2022-2024 driven by gas-linked wholesale prices. The Default Market Offer (DMO) for 2025-26 sits 4-12% higher than 2024-25 across all NEM states. Use 3.5% as a long-run escalation default; aggressive scenarios (high gas prices, increased grid charges) justify 4-5%. Higher escalation favours self-consumption value and pushes batteries closer to payback.