Solar Loan Calculator (Australia)
Free Australian solar loan calculator. Estimate the monthly repayment, total interest, and year-1 net cash flow on a financed residential PV system using current 2026 lender APRs and state feed-in tariffs.
Solar Loan Calculator
Monthly repayment
$120
Total paid over term
$10,046
Total interest
$2,246
Year-1 net monthly cash flow
$128
Positive — solar pays more than the loan
Annual amortisation schedule
| Year | Interest | Principal | Balance |
|---|---|---|---|
| 1 | $554 | $881 | $6,919 |
| 2 | $486 | $949 | $5,970 |
| 3 | $413 | $1,023 | $4,947 |
| 4 | $333 | $1,102 | $3,845 |
| 5 | $248 | $1,187 | $2,658 |
| 6 | $156 | $1,279 | $1,379 |
| 7 | $57 | $1,379 | $0 |
How to use this calculator
Enter four numbers and the calculator returns your monthly repayment, total paid over the term, total interest, and year-1 net monthly cash flow:
- Loan amount — the post-STC financed cost. The default A$7,800 reflects a CEC-approved 6.6 kW system at A$1,180/kW after the STC rebate (Clean Energy Council Industry Snapshot 2026 average). With a 10 kWh battery added, the financed amount typically rises to A$11,000-A$14,000 after the federal Cheaper Home Batteries Program rebate.
- APR — the comparison rate from your loan agreement. 2026 Australian ranges: Brighte Green Loan 6.49-8.49%, Plenti Green Loan 5.99-7.99%, Wisr Green Loan 7.99-9.99%, Latitude 8.99-12.99%, big-four green loans 5.99-7.49%. ACT Sustainable Household Scheme 0% (up to A$15,000, 10-yr term).
- Term — Australian solar loans run 5-15 years. Brighte caps at 10 years; Plenti goes to 7. Default 7 years matches typical Brighte product.
- Year-1 monthly bill savings — annual self-consumed kWh × your retail rate ÷ 12 + monthly feed-in tariff income. CEC reference 6.6 kW system in capital cities produces 9,000-10,500 kWh/year. With a 30% self-consumption split at A$0.33/kWh import + 70% export at A$0.06/kWh FiT = roughly A$2,977/yr or A$248/mo.
How the math works
Standard amortising-loan math (same as a mortgage or auto loan):
monthly_repayment = P × r / (1 - (1 + r)^-n)
where:
P = principal (post-STC financed amount, in AUD)
r = APR ÷ 12 (monthly rate, decimal)
n = term in monthsWorked example for the en-au defaults (A$7,800, 7.49% APR, 7 years):
- r = 0.0749 / 12 = 0.006242
- n = 84 months
- monthly = 7,800 × 0.006242 / (1 - 1.006242^-84) = A$119.21/month
- Total paid = 119.21 × 84 = A$10,014
- Total interest = A$10,014 - A$7,800 = A$2,214
Net cash flow = bill savings - repayment. With default A$248/mo savings, net = A$248 - A$119 = A$129/mo positive year 1 — Australian solar loans are typically the most cash-flow positive in the world thanks to the STC rebate and high retail tariffs.
Australian loan economics by capital city (2026 reference)
Based on Clean Energy Council, SunWiz Q1 2026, and AER DMO 2025-26 data — year-1 cash flow for a 6.6 kW system financed at A$7,800 / 7.49% / 7-yr term:
| City | Annual generation | Retail rate | FiT | Self-consumed savings | FiT income | Total monthly | Net vs A$119 |
|---|---|---|---|---|---|---|---|
| Adelaide | 9,800 kWh | 41 c | 5 c | A$120 | A$29 | A$149 | +A$30 |
| Perth | 10,200 kWh | 32 c | 3 c (DEBS peak 10 c) | A$98 | A$18 | A$116 | -A$3 |
| Sydney | 9,200 kWh | 35 c | 5 c | A$108 | A$27 | A$135 | +A$16 |
| Melbourne | 8,800 kWh | 30 c | 4 c | A$88 | A$21 | A$109 | -A$10 |
| Brisbane | 9,800 kWh | 33 c | 5 c | A$108 | A$28 | A$136 | +A$17 |
| Hobart | 7,800 kWh | 28 c | 6 c | A$73 | A$28 | A$101 | -A$18 |
| Darwin | 10,500 kWh | 28 c | 9 c (Jacana) | A$74 | A$55 | A$129 | +A$10 |
| Canberra | 9,000 kWh | 32 c | 7 c (ActewAGL) | A$96 | A$37 | A$133 | +A$14 |
The federal Cheaper Home Batteries Program (post-1 July 2025) shifts every city above into clearly positive territory once a battery is added — A$3,700-A$4,800 off install + retained self-consumption replaces the disappearing FiT economics.
Loan vs cash vs PPA — Australian comparison
| Option | Up-front cost | 25-year net | Break-even | Best for |
|---|---|---|---|---|
| Cash | A$7,800 | A$32,000+ savings | 3-4 yrs | Owners with cash and full STC capture |
| Loan (7-yr Brighte 7.49%) | A$0 down | A$28,000 savings | 4-5 yrs | Owners who want $0-down with retained ownership |
| Mortgage offset / redraw | Redraw fee | A$30,000 savings | 4-5 yrs | Owners with healthy redraw balance |
| State 0% loan (ACT/SA) | A$0 down | A$33,000 savings | 3 yrs | Owners in eligible state with up-front means test |
Australian solar loans economically dominate cash for most buyers because the STC rebate, high tariffs, and falling component prices have compressed payback to 3-5 years even at 7-8% APR.
What changes the loan economics
Helps
- State 0% loan programs (ACT Sustainable Household, SA Home Battery, NSW EAPA)
- Mortgage offset / redraw at 5.99-6.49% instead of 7-9% personal loan
- Battery + Cheaper Home Batteries A$370/kWh rebate flips export-heavy systems back to positive
- Time-of-use tariff with 25-50% afternoon peak premium (Origin SunSmart, AGL Solar Boost)
Hurts
- 5 kW DNO export limit in some states (especially WA/SA) — caps what you can export
- DEBS in WA at 10 c peak / 3 c off-peak — drives the WA case toward batteries instantly
- Demand-charge tariffs (Ergon Tariff 14, AusGrid demand) — solar reduces kWh but may not reduce demand
- Rent-a-roof / no-money-down PPA offers without ownership transfer — typically save 30-40% less than owner-financed
Pair this with the payback calculator, system cost calculator, and ROI calculator
The loan calculator gives you the monthly outgoing. Payback gives you the break-even year. Cost gives you the post-STC sticker. Run all three with your specific city tariff and a CEC-accredited installer’s quote before signing.
Sources
- Clean Energy Council — Industry Snapshot 2026 — installed cost, financing market share
- Clean Energy Regulator — STC scheme — STC mechanics, deeming period
- DCCEEW — Cheaper Home Batteries Program — A$370/kWh battery rebate
- AER — Default Market Offer 2025-26 — retail tariff benchmarks by NEM region
- SunWiz Q1 2026 Market Report — installed system cost trends
- AS/NZS 5033:2021 + AS/NZS 3000 — PV installation and wiring rules
Frequently asked questions
What APR should I expect on a 2026 Australian solar loan?
Q1 2026 Australian solar finance APRs range from 4.99% (Brighte Green Loan, Plenti Green Loan with battery for top-tier credit) to 9.99% on standard unsecured personal loans (Latitude, Wisr, Society One). Brighte and RateSetter dominate the dealer-finance market with 6.49-8.49% on no-fee 7-year terms. Several state Sustainability Loans offer 0% interest: SA Home Battery Scheme finance at 0% to 5 years, NSW EAPA, ACT Sustainable Household Scheme 0% over 10 years up to A$15,000.
How does the STC rebate interact with a financed system?
The Small-scale Technology Certificate (STC) rebate from the Clean Energy Regulator is point-of-sale: most CEC-approved installers register for STCs on your behalf and discount the rebate from the gross quote. The financed amount is therefore the post-STC price (typically A$5,500-A$9,500 for 6.6 kW). STCs deeming period dropped from 11 to 10 years on 1 January 2026 and steps to 9 years on 1 Jan 2027 under the SRES sunset. Your installer's quote should show STC value as a separate line — confirm before signing.
Should I take a solar loan or use my home loan offset?
Drawing from a home loan redraw or offset typically beats an unsecured solar loan by 200-500 basis points in 2026. Big-four mortgage rates 5.99-6.79% vs Brighte/Plenti at 6.49-8.49%. Caveats: drawing from offset reduces the offset balance permanently (you pay extra interest on the rest of the mortgage), and many lenders require a redraw fee. Run the maths both ways. Offset wins for borrowers with healthy redraw and full mortgage repayments; Brighte wins for owners who want a separate line of credit ring-fenced from the home.
What is the Cheaper Home Batteries Program?
Federal Cheaper Home Batteries Program launched 1 July 2025 — A$370/kWh upfront discount on CEC-approved batteries, capped at 50 kWh per residence. Stacks with state battery rebates (NSW Peak Demand Reduction Scheme, VIC Battery Loan A$8,800 interest-free, ACT Sustainable Household Scheme). Most 10-13 kWh batteries get A$3,700-A$4,800 off the install price. Brighte and Plenti finance the post-rebate amount. Confirm CEC approval and accreditation status before signing.
Is solar loan interest tax-deductible in Australia?
No, not for the principal residence. ATO rule: only loan interest on income-producing property is deductible. Owner-occupier solar loans are not deductible. Investment property solar IS deductible against rental income — useful for landlords. The economic gain on the principal residence is the bill savings + state feed-in tariff payments, both tax-free. Talk to your accountant if your home doubles as a registered home office (Schedule C-style apportionment may apply to a fraction).