Introduction
One of the most common surprises for new solar owners is how much generation changes between seasons. Your summer bill may look dramatically better than winter. Understanding seasonal export helps you set realistic payback expectations and avoid overestimating savings.
Why Seasonal Export Matters
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Summer: Longer days, higher sun angle, more generation.
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Winter: Shorter days, lower sun angle, more heating use (higher demand).
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Impact on FiT: Summer often produces surplus exports at lower value, while winter reduces export but increases import costs.
Check your region’s averages with Compare FiT by State and Postcode Estimator.
Worked Example 1 — Summer Export
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Location: Brisbane, 6.6 kW system
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Average summer output: 30 kWh/day
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Self-consumption: 40% = 12 kWh
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Exports: 18 kWh × 8c = $1.44/day
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Import offset: 12 kWh × 30c = $3.60/day
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Total saving: $5.04/day
Worked Example 2 — Winter Export
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Same system, winter output: 18 kWh/day
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Self-consumption: 60% = 10.8 kWh
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Exports: 7.2 kWh × 8c = $0.58/day
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Import offset: 10.8 kWh × 30c = $3.24/day
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Total saving: $3.82/day
Even though self-consumption share is higher in winter, total savings drop because overall generation is lower.
Worked Example 3 — Payback Impact
Annual average:
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Summer: $5.04 × 90 days = $454
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Winter: $3.82 × 90 days = $344
Seasonal swing = $110 difference per quarter.
Use the Solar ROI Fit Calculator and FiT Savings Calculator to project year-round savings.
FAQs
Q1. Why is summer output higher?
Because days are longer and the sun is higher in the sky, panels produce more energy.
Q2. Do winter bills always look worse?
Often yes, since you import more power for heating and export less solar.
Q3. Should I size my system for winter or summer?
It depends on goals. If you want year-round stability, size for winter. If you want maximum annual ROI, size for summer output.
Q4. How do retailers treat seasonal swings?
Some plans offer time-of-export FiTs that better reward winter evening exports. Compare options at Retailer Rates.
Conclusion
Seasonal export differences are real and significant. Summer boosts exports and bill credits, while winter trims both. Modeling these swings with the Rate Change Tracker gives you a realistic view of your solar ROI.