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Solar Panel Output Calculator (Australia)

Free Australian solar panel output calculator. Estimate daily, monthly, and 25-year kWh production from your array, sun hours, and system efficiency — plus dollar savings.

Prepared by the Solar Calculator HQ editorial team. Review our formula, source and limitation standards.

Solar Panel Output Calculator

Daily output
23.17 kWh
Monthly output
704 kWh
Annual output
8,456 kWh
Year-1 bill savings
$2,875
25-year output
199,179 kWh
25-year bill savings
$104,576

How to use this calculator

Enter six numbers and the calculator returns daily, monthly, annual, and 25-year energy output, plus dollar savings:

  1. Array size (W) — total panel wattage. A 6.6 kW system is 6,600 W (typical residential cap before retailer demand-management restrictions kick in).
  2. Peak sun hours per day — see capital city averages above. Default 4.5 is the Australian populated-region mean.
  3. System efficiency (%) — leave at 78%. Aligns with CEC sizing and Clean Energy Regulator MyTime calculations.
  4. Panel age (years) — 0 for new, 10 for ten years old.
  5. Electricity rate (A$/kWh) — AER median residential is 32–36 c/kWh in 2026, varying by state.
  6. Annual rate escalation (%) — Australian retail electricity has risen 3–5%/yr in the 2020s. Use 3.5% as a balanced default.

The formula

daily_kWh    = array_W × peak_sun_hours × derate / 1000
annual_kWh   = daily_kWh × 365
lifetime_kWh = sum over 25 years of annual_kWh × (1 - degradation)^year

A worked example for a 6.6 kW system in Brisbane:

  • 6,600 W × 4.8 sun-hr × 0.78 = 24.7 kWh per day
  • 24.7 × 30.4 = 750 kWh per month
  • 24.7 × 365 = 9,015 kWh per year
  • At 30 c/kWh (with 70% self-consumption + 30% export at 6 c): A$2,030 in year-1 bill savings
  • Lifetime (25 years, 0.5% degradation, 3.5% escalation): about A$73,500 in savings

Output reference table by system size

Using 4.5 peak sun hours, 78% derate, 0-year age, A$0.34/kWh, and 3.5% annual rate escalation:

System sizeDaily kWhMonthly kWhAnnual kWh25-yr kWh25-yr savings
5 kW17.65336,408150,400A$84,800
6.6 kW23.27048,460198,500A$112,000
8 kW28.185310,253240,600A$135,800
10 kW35.11,06612,816300,700A$169,700
13.3 kW46.61,41817,045400,000A$225,700
20 kW70.22,13325,632601,400A$339,400

Linear scaling — a 13.3 kW system produces exactly twice a 6.6 kW system.

What changes Australian output

Climate zone

The Clean Energy Regulator’s STC zones reflect the irradiance hierarchy: Zone 1 (Darwin, Alice, far-north Qld) gets 5.0–5.7 PSH; Zone 4 (Tasmania) gets 3.7. Zones 2 and 3 cover most populated areas at 4.2–4.8 PSH. SunWiz publishes annual production benchmarks per postcode.

Roof orientation

North-facing 30° tilt is the Australian reference (we’re in the Southern Hemisphere). East-west split cost 10–13% per year. South-facing is the worst case — 25–30% loss versus north. See the solar panel orientation calculator for your specific roof.

Heat derating

Australian summers are brutal on solar panels. A 35°C ambient day with full sun puts cell temperatures at 60–70°C, dropping output 14–18% from STC. Premium panels with -0.30%/°C coefficients (Tier-1 Trina Vertex S+, LONGi Hi-MO, REC Alpha) lose less than budget panels at -0.40%/°C.

Shading

Eucalypt trees, water tanks, and roof clutter are common Aussie shade sources. CEC-accredited installers must use Sunny Design or Skelion shade modelling. Optimisers or micro-inverters are essential on any partly shaded roof — the 10–15% premium pays back in 3–4 years on a 6.6 kW system.

Soiling

Bushfire smoke, red dust, and bird droppings cost 3–5% in arid inland; coastal salt spray adds 1–2%. Sydney and Melbourne rain rinses panels effectively — soiling stays under 2% annually. The solar panel cleaning cost calculator walks through whether annual cleaning is economic.

Why the 78% derate matches CEC

The Clean Energy Council sizing standard and the Clean Energy Regulator MyTime calculator both use 0.78 as the residential system performance factor. Components:

  • Inverter efficiency: 96–98% for modern CEC-listed inverters (Fronius, SMA, Sungrow, Goodwe)
  • DC and AC cabling: 2%
  • Soiling (annual average): 2%
  • Mismatch: 2%
  • Light-induced degradation (LID): 1.5% lifetime
  • Temperature derating: ~10% effective annual average for most populated zones

Multiply: ~0.78. Hot inland zones may run 75%; cooler southern installs with optimisers reach 82%.

Common Australian mistakes

  • Quoting US numbers: 5 PSH is Sydney’s summer peak, not annual average. Use BoM data, not random US sources.
  • Ignoring DNSP export limits: Many networks (Energex, Ergon, Endeavour) cap exports at 5 kW for residential. A 13 kW system that can only export 5 kW is leaving production on the table during midday — a battery is the answer.
  • Sizing too small to “match consumption”: A 6.6 kW system that exports 40% to grid at 6 c/kWh is still cheaper per kWh delivered than a 4 kW system that imports nothing extra. Bigger is usually better in 2026 economics.
  • Trusting sub-$1.00/W quotes: Tier-3 panels and budget inverters have higher degradation, shorter warranties, and higher long-term cost. Pay $1.05–1.15/W for Tier-1 hardware from a CEC-accredited installer.

Sources

Frequently asked questions

How much electricity does a 6.6 kW solar system produce per day in Australia?
About 23–28 kWh per day on average across most populated parts of Australia. The Clean Energy Council (CEC) zone ratings give 4.2 kWh/kWp/day in Sydney/Melbourne, 4.5 in Brisbane/Adelaide, and 5.0+ in Darwin and Alice Springs. Multiplied by 6.6 kWp and a 78% derate: 23–33 kWh/day depending on city. The CEC sizing guide and Clean Energy Regulator postcode zones are the authoritative references.
What are typical peak sun hours by Australian capital city?
Annual averages: Hobart 3.7, Melbourne 4.0, Sydney 4.4, Adelaide 4.6, Perth 4.9, Brisbane 4.8, Darwin 5.4, Alice Springs 5.7. The Bureau of Meteorology publishes daily global horizontal irradiance maps that confirm these. Tropical north has lower seasonal variation; southern states see winter dip to 2.5–3 PSH and summer peak of 5.5–6 PSH.
How are STCs accounted for in installed cost?
Small-scale Technology Certificates (STCs) are issued under the Renewable Energy Target. A 6.6 kW system installed in 2026 generates roughly 60–75 STCs depending on Zone (1, 2, 3, or 4). At an STC market price of $35–40, that's ~$2,400–3,000 deducted from gross install cost upfront. The CEC requires the installer to display both gross and net (after-STC) prices on the quote. Most Aussie quotes you see are already net of STCs.
How does the 30°C-plus Australian heat affect output?
Significantly. Cell temperature on a typical Aussie roof reaches 60–70°C on a 35°C ambient day. With a temperature coefficient of -0.4%/°C, that's 14–18% off rated wattage during peak hours. Tier-1 panels (LG, REC, Q CELLS, Trina Vertex S+) have improved coefficients down to -0.30%/°C. The 78% system derate captures the annual-average effect; instantaneous output on a hot afternoon can drop further.
What is the feed-in tariff (FiT) worth?
AER 2026 retail FiT data shows 4–8 c/kWh exported across most of NEM (Vic, NSW, SE Qld, SA), down from 6–10 c/kWh in 2024. WA's Synergy DEBS pays 2.5–10 c/kWh depending on time of day. The economic case is built on self-consumption first (29–34 c/kWh saved), exports second. A battery shifts midday excess to evening peak — the [solar panel ROI calculator](/calculators/solar-panel-roi-calculator/) models this.

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