Solar Panel Degradation Output Calculator
Project annual and cumulative energy if output decreases by a fixed percentage each year from the first-year estimate.
How to use this calculator
- Enter first-year energy output (kwh), annual degradation rate (%), years projected; check the units and use values from the same period or scenario.
- Review the result and intermediate values; change one input at a time when comparing scenarios.
- Keep the stated formula and assumptions with any result you share.
Formula and method
Year n output = first-year output × (1 − degradation rate)^(n − 1). Cumulative output is the sum of the projected annual outputs.
- Year 25 output is about 6,379 kWh; cumulative projected output is about 169,000 kWh.
- Actual yield depends on weather, availability, orientation, soiling, maintenance, component failure and the site. This is a scenario, not a warranty forecast.
Worked examples
Worked example
First-year output is 7,200 kWh with 0.5% degradation over 25 years.
Year 25 output is about 6,379 kWh; cumulative projected output is about 169,000 kWh.
Year 25 output is about 6,379 kWh; cumulative projected output is about 169,000 kWh.
Understanding the result
Year 25 output is about 6,379 kWh; cumulative projected output is about 169,000 kWh.
Actual yield depends on weather, availability, orientation, soiling, maintenance, component failure and the site. This is a scenario, not a warranty forecast.
Important notes
Actual yield depends on weather, availability, orientation, soiling, maintenance, component failure and the site. This is a scenario, not a warranty forecast.
Use measured inputs and verify that the model matches the situation before making an operational, financial or technical decision.
Frequently asked questions
Is degradation always constant each year?
No. A constant rate is a simple planning assumption.
Does this predict bill savings?
No. Energy value depends on tariffs, self-consumption, export rules and system costs.
What should I check before relying on this result?
Verify units, input definitions and assumptions against your real data or the relevant product, service or professional guidance.
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Related explanations
Learn the method behind the number or compare the terminology before using the calculator.
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This page provides a calculation tool plus explanatory information so you can understand what the result means and when the underlying method may not fit your situation.