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.
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?
The Small-scale Technology Certificate (STC) scheme effectively delivers an upfront rebate of $300-$500 per kW installed, depending on your zone (Zone 1: NT/north WA = highest, Zone 4: TAS = lowest) and the spot STC price (currently ~$36-$39 per certificate). For a 6.6 kW system in Zone 3 (most of NSW, VIC, SA, QLD), the rebate runs $2,700-$3,200, dropping a $10,500 gross install to ~$7,500. Most installers quote post-STC pricing. The deeming period reduces by one year each January, slowly winding the scheme down toward 2030.
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.