Solar Panel Estimate Calculator
Free solar estimate calculator for Australian homes. System size, annual generation, cost after STCs, year-1 bill savings under your DMO/VDO tariff, payback, and 25-year lifetime savings. 2026 Clean Energy Council and AER data.
Prepared by the Solar Calculator HQ editorial team. Review our formula, source and limitation standards.
Solar Panel Estimate Calculator
System size
4.68 kW
Annual production
6,000 kWh
Out-of-pocket cost
$4,917
Net cost after rebate
$4,917
Year-1 bill savings
$2,040
Simple payback
2y 5m
25-year lifetime savings
$74,206
Strong project — proceed
How to use this calculator
The estimator turns one number — your monthly kWh — into a full project view: system size, annual generation, out-of-pocket cost (after STCs), year-1 bill savings, payback in years and months, and a 25-year cumulative savings figure. Use it to sanity-check the first quote you receive before paying a deposit.
Inputs:
- Monthly electricity use (kWh) — average the last 12 bills. Australian Energy Regulator data shows the average residential consumption is around 5,500-6,000 kWh/yr in NSW/VIC/SA, 8,000 kWh/yr in QLD, 7,000 kWh/yr in WA, 9,000 kWh/yr in NT (cooling-dominated). Add 2,500-4,000 kWh/yr if you’ve added an EV.
- Target offset (%) — 100% sizes for full annual offset, but with low feed-in tariffs the value sits in self-consumption (typically 25-35% without battery, 65-80% with battery). NSW DNSP rules cap inverter export at 5 kW single-phase / 30 kW three-phase as default.
- Peak sun hours/day — BoM/CEC averages: Darwin 5.4, Brisbane 4.7, Perth 4.7, Adelaide 4.5, Sydney 4.4, Canberra 4.3, Melbourne 4.0, Hobart 3.7.
- Installed cost per watt (after STCs) — the all-in CEC-accredited turnkey price. SunWiz Q1 2026 median is A$1.05/W on 6.6 kW systems, falling to A$0.95/W on 10 kW. Below A$0.85/W typically signals tier-2 panels or under-scoped switchboard work.
- Additional rebate (%) — leave at 0 since STCs are already netted out. For state-specific rebates (Solar Victoria interest-free loan, NSW Empowering Homes, ACT Sustainable Household Scheme) the loan terms are not equivalent to a discount — model them separately.
- Electricity rate (A$/kWh) — the all-in rate from your bill (energy + supply charge averaged across kWh). 2026 averages: NSW 33c, VIC 30c, QLD Ergon/Energex 28c, WA 32c, SA 38c, TAS 27c, ACT 28c.
- Annual rate escalation (%) — AER DMO has averaged 3.5-5% annual nominal growth since 2018; 3.5% is a defensible long-run default.
How the math works
annual_target_kWh = monthly_kWh × 12 × (offset% / 100)
system_kW = annual_target_kWh / (peak_sun_hours × 365 × 0.78)
annual_generation = system_kW × peak_sun_hours × 365 × 0.78
out_of_pocket = system_kW × 1000 × A$/W (already post-STC)
year_1_savings = annual_generation × A$/kWh
simple_payback = out_of_pocket / year_1_savings
lifetime_savings = sum over 25 years of (generation × (1-0.005)^year × rate × (1+esc%)^year)The 0.78 derate factor follows CEC accreditation guidelines for grid-connected systems.
Worked example for a Sydney home using 5,500 kWh/yr at 33c/kWh:
- Annual target: 5,500 kWh
- System size: 5,500 / (4.4 × 365 × 0.78) = 4.39 kW
- Annual generation: 4.39 × 4.4 × 365 × 0.78 = 5,500 kWh
- Out-of-pocket at A$1.05/W: 4,390 × A$1.05 = A$4,610
- Year-1 savings: 5,500 × A$0.33 = A$1,815
- Simple payback: A$4,610 / A$1,815 = 2.5 years
- 25-year lifetime savings (3.5% esc): ~A$59,400
(Note: typical Sydney household sizing tends toward 6.6 kW for export-credit and self-consumption headroom, not just bill match.)
Australian payback ranges by capital city (2026)
SunWiz Q1 2026 + AER DMO data:
| City | PSH/day | A$/W (post-STC) | Avg rate c/kWh | Typical payback (6.6 kW) |
|---|---|---|---|---|
| Brisbane | 4.7 | A$1.00 | 28c | 3-4 yrs |
| Sydney | 4.4 | A$1.05 | 33c | 3-5 yrs |
| Melbourne | 4.0 | A$1.10 | 30c | 4-6 yrs |
| Perth | 4.7 | A$1.05 | 32c | 3-4 yrs |
| Adelaide | 4.5 | A$1.05 | 38c | 3-4 yrs |
| Hobart | 3.7 | A$1.15 | 27c | 5-7 yrs |
| Canberra | 4.3 | A$1.05 | 28c | 4-6 yrs |
| Darwin | 5.4 | A$1.20 | 31c | 4-5 yrs |
Sources: SunWiz Q1 2026 Australian PV Market Report, AER Default Market Offer 2025-26, BoM Solar Radiation Atlas, Clean Energy Council Approved Solar Retailers list.
What raises Australian payback above the headline
- East/west-facing roof: -10 to -15% production
- 30°+ pitch with morning shading from neighbouring trees: -15 to -25%
- Soiling in dust-belt regions (regional NSW, SA Riverland): -5 to -8% if not cleaned annually
- Hot-day derating (panels run 20-30°C above ambient — production drops 0.3-0.5%/°C): -3 to -5% annualised in QLD/NT/WA hot interior
- Export-limit DNSPs (Ergon, SA Power Networks, Western Power) capping export at 5 kW or curtailing dynamically: -5 to -15% on oversized systems
Pair this with the cost calculator, payback calculator, and ROI calculator
The estimator gives the headline numbers; the cost calculator drills into A$/W and adders (switchboard upgrade, three-phase isolator); the payback calculator splits simple from discounted payback; the ROI calculator turns the project into an IRR you can compare against an offset mortgage rate.
Sources
- Clean Energy Council — Approved Solar Retailers — retailer benchmarks
- SunWiz Q1 2026 Australian PV Market Report — installed price data
- AER Default Market Offer 2025-26 — regulated retail rate
- Clean Energy Regulator STC Scheme — STC values and deeming
- BoM Solar Radiation Atlas — peak sun hours
- Cheaper Home Batteries Program — A$370/kWh battery rebate
- Service.com.au Solar Pricing Index 2025 — quote benchmarking
Frequently asked questions
How accurate is this Australian solar estimate calculator?
Within ±10% of a CEC-accredited installer's quote for a typical detached home in NSW, VIC, QLD, WA, SA, TAS or the ACT. The model uses BoM/CEC peak-sun-hour averages, the 2026 SunWiz Q1 median residential price of A$1.05/W (already net of STCs), Tier-1 panel degradation (0.5%/yr), and a 3.5% tariff escalation aligned with AER Default Market Offer trajectory. Real production varies 8-20% with orientation, pitch and roof shading.
Are STCs already in the price?
Yes — the A$1.05/W default is the post-STC out-of-pocket price typical CEC-accredited retailers quote in 2026. Small-scale Technology Certificates under the Clean Energy Regulator's SRES scheme are assigned to your installer at signing and discount your invoice directly. The current STC value is around A$31-A$36/certificate (AEMO trade range Q1 2026), with deeming periods continuing to step down (2026: 9 years; 2027: 8 years; 2028: 7 years; phasing out 2030).
How does the Cheaper Home Batteries Program affect savings?
The federal Cheaper Home Batteries Program effective 1 July 2025 provides a 30% upfront discount on small-scale battery systems (5-50 kWh) installed alongside or after a CEC-accredited solar PV system, equivalent to about A$370/kWh of nominal capacity. A 10 kWh Tesla Powerwall 3 retailing around A$13,500 installed becomes roughly A$9,800 after the rebate. Battery raises self-consumption from 25-35% to 65-80% on a typical 6.6 kW system, lifting year-1 savings by A$700-A$1,200.
What feed-in tariffs apply in 2026?
Feed-in tariffs in 2026 are typically 4-8c/kWh exported, well below retail import (28-38c/kWh): NSW around 4.9-7.0c (Origin Solar Boost 9.5c first 12kWh/day), VIC mandatory minimum 0.04c with retailers paying 4.9c blended, QLD Energex 4.4c, WA Synergy DEBS 2.5c off-peak / 10c peak, SA AGL 4.7c, TAS Aurora 8.94c, ACT ActewAGL 8.0c. With low FiTs the calculator assumes self-consumption is the value driver — pair PV with battery and load shifting to maximise return.
Is solar still worth it in Australia in 2026?
Yes — short payback periods are the norm. The 2026 AER Default Market Offer for residential customers in NSW/VIC/SA averages 32-38c/kWh blended, against an out-of-pocket installed price near A$6,930 for a 6.6 kW system (Sunwiz Q1 2026). Payback is typically 4-6 years and 25-year lifetime savings reach A$28,000-A$45,000 on a south-facing 6.6 kW Sydney/Brisbane/Adelaide system, even before the Cheaper Home Batteries Program discount.