Calculator
Solar ROI Calculator โ Australia
Estimate Australian solar payback from your state or territory, monthly bill, and project year
Going solar is a financial decision as much as an environmental one. This calculator starts with inputs most Australian homeowners know: state or territory, monthly electric bill, and project year. RenewableCalc then applies local electricity-rate, installed-cost, production, STC rebate, and feed-in tariff defaults while keeping advanced inputs editable. The result is a planning estimate for payback, net upfront cost, 25-year savings, bill offset, policy caveats, and a solar quote checklist for reviewing installer assumptions.
All estimates use A$ / Australia local data: electricity rates, solar costs, and incentives.
Quick estimate State Monthly bill Project year
Enter Your Details
Start with the required inputs. Open advanced assumptions when you have a quote or utility details.
Fill in the form and click Calculate to see results.
Before You Sign
Check for these red flags in any solar quote before committing to a contract.
- System size significantly larger than your annual usage
- Estimated annual production seems too optimistic
- Battery storage bundled without clear need analysis
- Warranty or production guarantee is vague or missing
- Price per watt above $3.50 without justification
- "Free solar" or "no cost" language (usually a lease/PPA with hidden costs)
- APR on loan exceeds 7โ8% without explanation
STC values change annually on 1 January. State feed-in tariffs and battery rebates vary โ check your state scheme. Read the policy details
Policy status
Australian solar and battery incentive policy status
Australian incentive assumptions depend on the project year. Small-scale Technology Certificates (STCs) under the Renewable Energy Target reduce upfront system cost. State-based feed-in tariffs, battery rebates, and interest-free loans vary by state โ verify current STC values and state schemes with the Clean Energy Regulator before treating any estimate as final.
Policy last reviewed: 2026-06-09 ยท Source: Clean Energy Regulator STC scheme and AEMO electricity data.
Data Sources
Assumptions behind this calculator
Electricity rates
AEMO and state tariff benchmarks
Uses Australian state and territory residential electricity-rate references when the user leaves electricity rate blank.
Installation costs
Solar Choice Price Index
Uses Australian residential solar installed-cost benchmarks by state and territory.
Solar production
BOM and PVGIS-CMSAF
Uses Australian sunlight and peak-sun-hour defaults when system size is estimated.
Incentives
Clean Energy Regulator STC scheme
Small-scale Technology Certificates reduce upfront cost; state battery rebates and feed-in tariffs vary by location and retailer.
Overview
Going solar is a financial decision as much as an environmental one. This calculator starts with inputs most Australian homeowners know: state or territory, monthly electric bill, and project year. RenewableCalc then applies local electricity-rate, installed-cost, production, STC rebate, and feed-in tariff defaults while keeping advanced inputs editable. The result is a planning estimate for payback, net upfront cost, 25-year savings, bill offset, policy caveats, and a solar quote checklist for reviewing installer assumptions.
Use this result
Use the calculator inputs first, then compare the result against local rates, incentives, roof conditions, and utility export rules.
Method, assumptions, and sourcesOpen this section when you want to audit the calculation behind the estimate.ShowHide
Calculation Method
ROI = (lifetime savings - net system cost) / net system cost
Key Assumptions
- State, monthly electric bill, and project year are the minimum inputs for a planning estimate.
- Federal residential credit assumptions depend on project year; 2026+ projects default to no federal residential credit.
- 25-year system life
- 0.5% annual panel degradation
Data Sources
Electricity rates
AEMO and state tariff benchmarks
Uses Australian state and territory residential electricity-rate references when the user leaves electricity rate blank.
Installation costs
Solar Choice Price Index
Uses Australian residential solar installed-cost benchmarks by state and territory.
Solar production
BOM and PVGIS-CMSAF
Uses Australian sunlight and peak-sun-hour defaults when system size is estimated.
Incentives
Clean Energy Regulator STC scheme
Small-scale Technology Certificates reduce upfront cost; state battery rebates and feed-in tariffs vary by location and retailer.
Result Summary
Strong fit
Payback under 8 years
Good fit: usually worth deeper quote comparison, especially with high local electricity rates.
Borderline
Payback 8-12 years
Needs review: check roof condition, financing, battery needs, and utility export rules before committing.
Weak fit
Payback over 12 years
Weak financial case: solar may still help resilience or emissions goals, but the financial case needs scrutiny.
Assumptions Data Sources Related Links
How to Use This Calculator
Select your state or territory, enter your average monthly electric bill, and set the project year. Leave system size, installation cost, electricity rate, and incentives blank if you want RenewableCalc to use Australian defaults. Edit advanced fields when you have a real installer quote, retailer tariff, feed-in tariff, or state battery rebate. The result shows payback period, net upfront cost, 25-year net savings, estimated system size, bill offset, assumptions used, next-step actions, and a quote-review checklist covering installed cost per watt, production, STC treatment, feed-in tariff value, battery scope, financing, and roof work.
Formula & Methodology
ROI is calculated using a discounted cash flow model: NPV = ฮฃ (Annual Savings / (1 + Discount Rate)^Year) - Net Investment. Payback period = Net Investment / Annual Savings. Australian defaults use state or territory electricity-rate references, local installed-cost benchmarks, STC rebate estimates, feed-in tariff assumptions, 25-year system life, and 0.5% annual panel degradation. State battery rebates and retailer feed-in tariffs vary, so advanced fields remain editable.