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.
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.