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Panel Degradation

Capacity remaining after N years at given degradation.

Performance

Inputs (SI units)

Light-induced degradation applied once, in year 1.

Results

Capacity at year 25
8.632 kWp
Percent of nameplate remaining
86.32 %
Total degradation over period
13.68 %
Year-1 capacity (post-LID)
9.8 kWp
Cumulative lifetime energy
346,060 kWh
Year-1 energy
14,700 kWh
Year-25 energy
12,949 kWh
Modelled vs warranty at year 25
86.32 % modelled vs 84.8 % guaranteed
✓ PASS — Annual degradation rate is within the modern module range (≤0.8%/yr).
✓ PASS — Modelled degradation curve stays above the manufacturer's warranty floor.

Engineering Recommendations

  • →Energy figures assume a constant year-1 specific yield scaled by remaining capacity; real-world weather variability will shift year-to-year energy independent of degradation.
  • →Always cross-check against the manufacturer's linear or step-wise performance-warranty curve, not just a flat annual rate.
  • →Engineering-grade preliminary calculation. Final design must be verified against project-specific site conditions, manufacturer datasheets, applicable standards and utility requirements.

Detailed Calculation Log

Year-by-year capacity computed for 25 years: LID 2% in year 1, then 0.55%/yr linear-compounded thereafter.

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Engineering Formula

  • P(1) = P0 × (1 − LID%)
  • P(t) = P(1) × (1 − annualDeg%)^(t−1) for t ≥ 2
  • E(t) = P(t) × specificYield_y1 × (P(t)/P0) — energy scales with remaining capacity
  • Cumulative lifetime energy = Σ E(t)

Modern mono-PERC / TOPCon shows 2% year-1 light-induced degradation, then 0.4–0.55%/yr linear. Warranties typically guarantee 80–85% at year-25.

Step-by-step Calculation

  1. 1.Year-1 capacity (post-LID)P0×(1−LID%)9.8 kWp
  2. 2.Year-25 capacityP(1)×(1−d)^(t−1)8.632 kWp
  3. 3.Year-1 energyP(1)×specificYield14,700 kWh
  4. 4.Cumulative lifetime energy (25 yr)Σ P(t)×specificYield346,060 kWh
  5. 5.Total % degradation over period1 − P(final)/P013.68 %
  6. 6.Modelled capacity at warranty year 25P(t)/P086.32 %
  7. 7.Warranty guaranteed floorinput84.8 %

How to use this calculator: Panel Degradation

Capacity remaining after N years at given degradation. The example below is calculated by this page's real engine from the displayed inputs.

  1. 1Confirm that the Panel Degradation matches the quantity or design check you need.
  2. 2Enter Initial rated capacity, First-year (LID) degradation, and Annual degradation (year 2 onward) using the units printed beside each field.
  3. 3Check every value before calculating, especially decimal points and measurement units.
  4. 4Calculate, then follow the substituted equations in the worked example and compare the result with any stated limit.
  5. 5Read the assumptions, warnings and cited references before using the result for a financial, medical or engineering decision.

Input guide and example values

Use values from the same measurement basis and time period. Conditional fields appear only when the related option is selected.

InputExample valueWhy it matters
Initial rated capacity10 kWpMeasured or known initial rated capacity used by the calculation engine.
First-year (LID) degradation2 %Light-induced degradation applied once, in year 1.
Annual degradation (year 2 onward)0.55 %/yrMeasured or known annual degradation (year 2 onward) used by the calculation engine.
Analysis period25 yrMeasured or known analysis period used by the calculation engine.
Year-1 specific yield1500 kWh/kWp/yr0/blank skips the lifetime-energy calculation.
Warranty check-year25 yrOptional input; leave the supplied default only when it matches your case.
Warranty guaranteed capacity at that year84.8 % of nameplate0/blank skips the warranty-floor check.

Formula inputs & variables for Panel Degradation

These are the named quantities used by this calculator. When the source formula does not define a mathematical symbol, OneCalcApp keeps the real input label instead of inventing one.

Variable / inputUnitMeaning in this calculation
Initial rated capacitykWpMeasured or known initial rated capacity used by the calculation engine.
First-year (LID) degradation%Light-induced degradation applied once, in year 1.
Annual degradation (year 2 onward)%/yrMeasured or known annual degradation (year 2 onward) used by the calculation engine.
Analysis periodyrMeasured or known analysis period used by the calculation engine.
Year-1 specific yieldkWh/kWp/yr0/blank skips the lifetime-energy calculation.
Warranty check-yearyrOptional input; leave the supplied default only when it matches your case.
Warranty guaranteed capacity at that year% of nameplate0/blank skips the warranty-floor check.

How the Panel Degradation works

The Panel Degradation uses Initial rated capacity, First-year (LID) degradation, Annual degradation (year 2 onward), Analysis period, Year-1 specific yield, Warranty check-year, and Warranty guaranteed capacity at that year to calculate Capacity at year 25, Percent of nameplate remaining, Total degradation over period, Year-1 capacity (post-LID), Cumulative lifetime energy, Year-1 energy, Year-25 energy, and Modelled vs warranty at year 25. Its engine applies P(1) = P0 × (1 − LID%); the worked values below come from that same live calculation rather than a separately typed example.

With Initial rated capacity 10 kWp, First-year (LID) degradation 2 %, Annual degradation (year 2 onward) 0.55 %/yr, Analysis period 25 yr, Year-1 specific yield 1500 kWh/kWp/yr, Warranty check-year 25 yr, and Warranty guaranteed capacity at that year 84.8 % of nameplate, the main worked-example result is Capacity at year 25 = 8.632 kWp.

How each Panel Degradation input is used

Initial rated capacity

The Panel Degradation worked example uses Initial rated capacity = 10 kWp. This value is passed directly into the calculation, with an allowed minimum 0.1.

First-year (LID) degradation

The Panel Degradation worked example uses First-year (LID) degradation = 2 %. This value is passed directly into the calculation, with an allowed minimum 0 and maximum 10. Light-induced degradation applied once, in year 1.

Annual degradation (year 2 onward)

The Panel Degradation worked example uses Annual degradation (year 2 onward) = 0.55 %/yr. This value is passed directly into the calculation, with an allowed minimum 0.05 and maximum 3.

Analysis period

The Panel Degradation worked example uses Analysis period = 25 yr. This value is passed directly into the calculation, with an allowed minimum 1 and maximum 40.

Year-1 specific yield

The Panel Degradation worked example uses Year-1 specific yield = 1500 kWh/kWp/yr. This value is passed directly into the calculation, with an allowed minimum 0. 0/blank skips the lifetime-energy calculation.

Warranty check-year

The Panel Degradation worked example uses Warranty check-year = 25 yr. This value is passed directly into the calculation, with an allowed minimum 1 and maximum 40.

Warranty guaranteed capacity at that year

The Panel Degradation worked example uses Warranty guaranteed capacity at that year = 84.8 % of nameplate. This value is passed directly into the calculation, with an allowed minimum 50 and maximum 100. 0/blank skips the warranty-floor check.

Panel Degradation formulas and result interpretation

Formula 1: relationship used

In the Panel Degradation, P(1) = P0 × (1 − LID%). The quantities in this relationship come from the named inputs or from an earlier calculation step shown in the worked example.

Formula 2: relationship used

In the Panel Degradation, P(t) = P(1) × (1 − annualDeg%)^(t−1) for t ≥ 2. The quantities in this relationship come from the named inputs or from an earlier calculation step shown in the worked example.

Formula 3: relationship used

In the Panel Degradation, E(t) = P(t) × specificYield_y1 × (P(t)/P0) — energy scales with remaining capacity. The quantities in this relationship come from the named inputs or from an earlier calculation step shown in the worked example.

Formula 4: relationship used

In the Panel Degradation, Cumulative lifetime energy = Σ E(t). The quantities in this relationship come from the named inputs or from an earlier calculation step shown in the worked example.

Capacity at year 25

For the displayed Panel Degradation worked example, Capacity at year 25 is 8.632 kWp. Verify Initial rated capacity, First-year (LID) degradation, and Annual degradation (year 2 onward) and their units before relying on this output.

Percent of nameplate remaining

For the displayed Panel Degradation worked example, Percent of nameplate remaining is 86.32 %. Verify Initial rated capacity, First-year (LID) degradation, and Annual degradation (year 2 onward) and their units before relying on this output.

Total degradation over period

For the displayed Panel Degradation worked example, Total degradation over period is 13.68 %. Verify Initial rated capacity, First-year (LID) degradation, and Annual degradation (year 2 onward) and their units before relying on this output.

Year-1 capacity (post-LID)

For the displayed Panel Degradation worked example, Year-1 capacity (post-LID) is 9.8 kWp. Verify Initial rated capacity, First-year (LID) degradation, and Annual degradation (year 2 onward) and their units before relying on this output.

Cumulative lifetime energy

For the displayed Panel Degradation worked example, Cumulative lifetime energy is 346,060 kWh. Verify Initial rated capacity, First-year (LID) degradation, and Annual degradation (year 2 onward) and their units before relying on this output.

Year-1 energy

For the displayed Panel Degradation worked example, Year-1 energy is 14,700 kWh. Verify Initial rated capacity, First-year (LID) degradation, and Annual degradation (year 2 onward) and their units before relying on this output.

Year-25 energy

For the displayed Panel Degradation worked example, Year-25 energy is 12,949 kWh. Verify Initial rated capacity, First-year (LID) degradation, and Annual degradation (year 2 onward) and their units before relying on this output.

Modelled vs warranty at year 25

For the displayed Panel Degradation worked example, Modelled vs warranty at year 25 is 86.32 % modelled vs 84.8 % guaranteed. Verify Initial rated capacity, First-year (LID) degradation, and Annual degradation (year 2 onward) and their units before relying on this output.

Panel Degradation accuracy, checks and limitations

  • Panel Degradation units check: confirm Initial rated capacity (kWp), First-year (LID) degradation (%), Annual degradation (year 2 onward) (%/yr), Analysis period (yr), Year-1 specific yield (kWh/kWp/yr), Warranty check-year (yr), and Warranty guaranteed capacity at that year (% of nameplate) before calculating.
  • Panel Degradation result check: compare Capacity at year 25, Percent of nameplate remaining, Total degradation over period, Year-1 capacity (post-LID), Cumulative lifetime energy, Year-1 energy, Year-25 energy, and Modelled vs warranty at year 25 with the substituted formula steps and the displayed rounding precision.
  • Panel Degradation: Use this result for preliminary design and cross-checking. Confirm the applicable code edition, manufacturer data, site conditions and qualified-engineer approval before final design or installation.

Understanding the result

Read the main result together with supporting checks, assumptions, limits and intermediate values.

For a manual check, repeat the first equation, confirm the units and change one input at a time.

Common mistakes when using Panel Degradation

  • Do not mix units for Initial rated capacity (kWp), First-year (LID) degradation (%), Annual degradation (year 2 onward) (%/yr). A unit mismatch changes the input magnitude even when the typed number looks reasonable.
  • Do not replace the displayed P(1) = P0 × (1 − LID%) relationship with a different convention without also changing the underlying assumptions; compare like-for-like methods when checking the result.
  • Do not treat Capacity at year 25 = 8.632 kWp from the worked example as a universal answer. It belongs to the displayed example inputs and must be recalculated for the actual case.

When the Panel Degradation is useful

Panel Degradation is designed for cases where Initial rated capacity, First-year (LID) degradation, Annual degradation (year 2 onward), Analysis period are known and you need Capacity at year 25, Percent of nameplate remaining, Total degradation over period. The page keeps the live calculator, calculation method and worked example together so the result can be checked instead of treated as a black-box number.

Use the calculator for the scope described by its inputs and notes. The displayed method is P(1) = P0 × (1 − LID%). If the real project or decision needs factors that are not represented here, treat the result as an estimate and add the missing checks separately.

Initial rated capacity and First-year (LID) degradation: what changes the answer

The worked example uses Initial rated capacity = 10 kWp, First-year (LID) degradation = 2 %, Annual degradation (year 2 onward) = 0.55 %/yr, Analysis period = 25 yr. With those values, Capacity at year 25 is 8.632 kWp. Changing an input should be interpreted according to that field's unit, range, option and hint rather than by the number alone.

For this calculator, the main input roles are: Initial rated capacity (kWp): Measured or known initial rated capacity used by the calculation engine. First-year (LID) degradation (%): Light-induced degradation applied once, in year 1. Annual degradation (year 2 onward) (%/yr): Measured or known annual degradation (year 2 onward) used by the calculation engine. Analysis period (yr): Measured or known analysis period used by the calculation engine.

How to sanity-check a Panel Degradation result

Start by confirming the entered values and units, then compare the substituted working with the displayed formula or calculation steps. Pay particular attention to Capacity at year 25, because it is the first worked-example output shown by the live engine.

Finally, compare the result with the assumptions, warnings and related calculators on this page. A nearby calculator can be useful as a cross-check when it measures the same workflow from a different input or output direction.

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Standards, source trail and limitations

References show the method used. Check the current local edition, amendments and project specification before a regulated decision.

Design Assumptions

  • • Constant post-year-1 degradation.
  • • No hot-spot / PID failures.

Engineering Tips

  • ◆Ask for datasheet linear warranty curve.
  • ◆TOPCon and HJT often warrant ≥ 87.4% at Y25.

Warnings

  • ▲Degradation > 1%/yr indicates PID or moisture ingress — investigate.

Standards & References

IEC 61215IEC TS 63209 (extended stress)

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