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Free Solar Draft Tool
Solar ROI & Payback Calculator
Enter your system cost, subsidy and monthly savings — Solar Draft shows your payback period and 25-year return.
Payback Period
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Net cost after subsidy—
Annual savings (Year 1)—
Total savings over 25 years—
Return on investment—
DisclaimerEstimates only. Assumes 0.5% annual panel output degradation and constant electricity tariffs; real savings will vary with tariff changes, actual generation and maintenance. Not financial advice.
How payback period is calculated
Payback period is the single number most people care about: how long until the system pays for itself.
- Net cost = system cost minus subsidy.
- Payback period = net cost ÷ annual savings in year one.
- 25-year savings accounts for a small annual output drop (about 0.5%/year), which is normal for solar panels.
For the math behind the numbers, see Solar ROI: How to Calculate Payback Period and Solar Panel Degradation Explained on the Solar Draft blog.
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