Solar Panel Payback Calculator (Australia)

How to use this calculator

Enter five numbers and the calculator returns net cost (after STC rebate), payback period in years and months, year-1 savings, and year-1 simple ROI:

1. Installed system cost — net price quoted by your CEC-accredited retailer after STCs are deducted at point of sale (most installers quote net). 2026 typical: $0.95-$1.20 per watt installed for a 6.6 kW system after STC rebate, or $6,300-$7,900 net for a 6.6 kW system.
2. Annual production (kWh) — first-year output. CEC rule of thumb: 1,300-1,500 kWh/kW for the major capitals (Brisbane, Sydney, Adelaide, Perth), 1,150-1,300 kWh/kW for Melbourne, Hobart, Canberra. Use the SunWiz solar yield map or PVWatts (set to BoM TMY data) for an address-specific estimate.
3. Electricity rate ($/kWh) — your blended retail import rate. AER 2025-26 DMO benchmarks: NSW 33-37c, SE QLD 32-35c, SA 38-42c, VIC 28-32c (under VDO), WA 32c, Tas 32c. Look at your bill: peak + shoulder + supply charge ÷ kWh.
4. Annual rate escalation (%) — SunWiz default: 3%. AEMC forecast 2025-30: 2-4%.
5. STC rebate (%) — already deducted if your installer quoted net. If quoted gross, enter 25-32% depending on your zone (Zone 1 highest, Zone 4 lowest). The Clean Energy Regulator publishes the deemed STCs by postcode.

How the math works

Australian solar payback uses an export-split formula because residential self-consumption sits at 25-40% without a battery:

year_n_self_consumption_savings = annual_kWh × self% × (1 - 0.005)^(n-1) × import_rate × (1 + escalation)^(n-1)
year_n_export_revenue           = annual_kWh × (1 - self%) × (1 - 0.005)^(n-1) × FIT
year_n_total_savings            = self_consumption_savings + export_revenue
cumulative_n                    = sum from year 1 to year n
net_cost                        = system_cost × (1 - rebate%/100)
payback_year                    = first year where cumulative_n >= net_cost

Worked example for a typical Sydney home:

• System: 6.6 kW, $7,200 net installed (after STC rebate, post-2024 pricing)
• Production: 9,200 kWh year 1 (BoM Sydney TMY, 4° tilt north-facing)
• Self-consumption split: 30% used, 70% exported
• Import rate: 35c/kWh (AGL Anytime Saver, NSW DMO benchmark)
• Export rate: 6c/kWh (post-2024 NSW retailer average)
• Year 1 savings: (2,760 × $0.35) + (6,440 × $0.06) = $966 + $386 = $1,352
• Year 5 cumulative (with 3.5% escalation, 0.5% degradation): about $7,300
• Payback: 5.0 years

The calculator above uses a single blended rate input — for the Australian export-heavy reality, use a blended rate of (self% × import) + ((1 - self%) × FIT). For 30% self-consumption: 0.30 × 0.35 + 0.70 × 0.06 = 0.147 = 14.7c effective.

Payback by Australian capital city (2026 reference)

Based on SunWiz, CEC, and AER 2025-26 DMO data for a typical 6.6 kW north-facing system:

Higher self-consumption households (battery, EV, heat pump split system) typically knock 6-12 months off these figures.

What changes the payback period

Compresses payback

• High retail rates — SA homes pay 38-42c/kWh, the highest in Australia.
• High self-consumption — daytime EV charging, hot-water-on-solar diversion (Catch Power / Paladin), pool pump scheduling.
• Cheaper Home Batteries Program rebate — federal $370/kWh for 5-50 kWh batteries from 1 July 2025.
• State battery rebates — NSW Battery Incentive ($1,500-$2,400), VIC Solar Homes battery loan, ACT Sustainable Household Scheme zero-interest loan.
• TOU export tariffs — AGL, Energy Locals, Amber Electric pay wholesale + a margin (often 15-30c on summer afternoons).

Extends payback

• Low feed-in tariffs — major NSW/QLD retailers dropped from 12c to 6c in 2024-25.
• VPP minimum exports — some battery rebate programs require 4-day-per-year curtailment to grid.
• Network capacity limits — ZNet zones in SA and WA limit export to 1.5-5 kW, reducing FIT revenue.
• Switchboard upgrade — older homes may need a $1,000-$2,500 switchboard upgrade for 6.6 kW systems.
• Tile or asbestos roofing surcharge — adds $500-$1,500.

Payback vs. ROI vs. lifetime savings

• Payback period answers “When do I break even?” — Australian average: 4 to 5 years.
• Lifetime ROI answers “What is my total return?” — typically 350-550% over 25 years (best in the world for residential).
• IRR answers “What annualised return does this match?” — typically 12-18% for Australian rooftop solar, beating most super fund returns.

See our solar ROI calculator for full IRR analysis and savings calculator for year-by-year cash flow.

Pair this with our ROI calculator, system cost calculator, and savings calculator

Always insist on a CEC-accredited installer and CEC-listed module + inverter — non-CEC kit cannot create STCs and voids most state battery rebates.

Sources

• Clean Energy Council — Buying solar guide — installer + product accreditation
• Clean Energy Regulator — STC scheme — STC mechanics and zone map
• AER Default Market Offer 2025-26 — quarterly residential price benchmarks
• SunWiz Australian Photovoltaic Insights — installation cost and yield benchmarks
• DCCEEW Cheaper Home Batteries Program — federal $370/kWh battery rebate
• Bureau of Meteorology TMY data — typical-meteorological-year solar irradiance