Introduction
Solar payback is the number of years it takes for your system to recover its upfront cost through bill savings and export credits. While averages are often quoted, your actual payback depends on multiple factors. This guide highlights what makes the biggest difference and shows you how to model your own results.
Key Factors That Affect Payback
-
System size and cost — Larger systems save more but cost more upfront.
-
Self-consumption ratio — The more solar you use directly, the faster the payback.
-
FiT (feed-in tariff) — Higher export rates improve returns, but caps and thresholds can reduce impact.
-
Import tariff — Lower import rates stretch the payback, while higher ones shorten it.
-
Daily supply charge — High fixed charges add to your bill regardless of solar savings.
-
Seasonal generation — Winter outputs can slow ROI if you rely on year-round savings.
Check Retailer Rates and Compare FiT by State to see your options.
Worked Example 1 — High Self-Consumption
-
System: 6.6 kW, cost $5,000
-
Generation: 25 kWh/day
-
Self-consumption: 70% (17.5 kWh)
-
Imports avoided: 17.5 × 30c = $5.25/day
-
Exports: 7.5 kWh × 8c = $0.60/day
-
Total saving = $5.85/day ≈ $2,135/year
-
Payback = 2.3 years
Worked Example 2 — Low Self-Consumption
-
Same system, but self-consumption = 30% (7.5 kWh)
-
Imports avoided: $2.25/day
-
Exports: 17.5 × 8c = $1.40/day
-
Total saving = $3.65/day ≈ $1,330/year
-
Payback = 3.8 years
Self-consumption makes a huge difference.
Worked Example 3 — Higher FiT Scenario
If FiT rises from 8c to 15c:
-
Exports: 17.5 × 15c = $2.63/day instead of $1.40/day
-
Total saving = $4.88/day ≈ $1,780/year
-
Payback = 2.8 years
FiT changes help, but less than improving self-consumption.
Use the Solar ROI Fit Calculator and FiT Savings Calculator to test your own setup.
FAQs
Q1. What has the biggest impact on payback?
Self-consumption usually matters most because every kWh you use saves you the full retail import rate.
Q2. Can retailer choice change payback?
Yes. Different retailers offer different FiTs, import tariffs, and supply charges. Compare at Retailer Rates.
Q3. Does system size affect payback?
A bigger system doesn’t always mean faster payback. Oversizing leads to more exports at lower FiT rates.
Q4. How often should I recalc payback?
At least once a year, since tariffs and FiTs change. The Rate Change Tracker helps you stay updated.
Conclusion
The single biggest driver of payback is how much of your solar you consume directly. FiT rates, tariffs, and system size also matter, but self-consumption has the most powerful effect. By modeling your numbers with tools like the Postcode Estimator, you’ll get a clear picture of what changes your payback the most.