Solar Degradation Year-N Production Chart

Use this worksheet after the calculator result, first-year production, and loss-stack review to carry annual degradation, year-N kWh, year-25 output, replacement notes, maintenance notes, and warranty-review notes into ROI, emissions, storage, and long-term owner review.

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Quick reference table

A solar degradation year-N production chart is a calculator-led worksheet for long-term PV output. It applies a user-entered annual degradation rate to first-year kWh, records year-N kWh and year-25 output, and keeps maintenance, replacement, ROI, emissions, storage, and warranty assumptions visible without guaranteeing production.

Long-term solar production worksheet

Long-term solar production worksheet
Field	Record on worksheet	Why it matters
Production basis	First-year kWh, PVWatts or model source, date retrieved, loss-stack link	Long-term output should start from the same documented first-year case
Degradation basis	Annual degradation rate, manufacturer or measured basis, climate or mounting note	The rate drives year-N kWh and should not be treated as universal
Year-N output	Selected year, year-N kWh, percent of first-year output	ROI, emissions, and storage screens may use different operating years
Year-25 output	Year-25 kWh, year-25 percent, warranty-review note	A 25-year view supports long-term comparison without deciding warranty eligibility

Long-term documentation fields

Long-term documentation fields
Documentation use	Worksheet field	Boundary
ROI and payback	Year-N kWh, O&M note, replacement note, degradation rate	Cash-flow models should show which production year is being used
Emissions	Selected-year kWh, factor source, degradation basis	Avoided emissions should not reuse first-year kWh when long-term output is intended
Storage	Year-N kWh, seasonal note, maintenance or availability note	Battery dispatch screens need usable production assumptions by year
Warranty review	Warranty term, product note, year-25 output, maintenance record	The worksheet records review inputs but does not determine warranty status

Formula basis

Year-N kWh = first-year kWh x (1 - annual degradation rate) ^ (N - 1). Year-25 output = first-year kWh x (1 - annual degradation rate) ^ 24.

First-year kWh is the selected production case after resource, tilt, orientation, and loss-stack assumptions are documented.
Annual degradation rate is the user-entered module or system degradation assumption from manufacturer data, measured performance, installer model, or owner planning basis.
N is the operating year being reviewed; year 1 uses the first-year production value.
Year-N kWh is the estimated production for the selected year after applying the documented degradation rate.
Year-25 output is a planning value for long-term comparison and warranty review notes, not a guarantee of production.
Replacement and maintenance notes record inverter replacement, cleaning, inspection, module replacement, monitoring, or repowering assumptions that affect long-term output.

Worked examples

Residential year-25 production checkStart with first-year kWh from the solar output worksheet, enter the documented degradation rate, calculate year-25 output, and attach cleaning, inverter replacement, and warranty-review notes before ROI inputs.

Commercial storage scenario inputsRecord year-N kWh for the operating year used in a storage scenario, then carry degradation, maintenance, availability, and replacement assumptions into battery dispatch and emissions worksheets.

Assumptions. Balanced load and line-to-line voltage assumptions behind this chart.

The worksheet is a planning record and does not certify long-term production, module performance, warranty eligibility, system life, emissions reporting, storage dispatch, or financial performance.
No degradation rate is assumed by default; users should document the manufacturer, measured, installer, PVWatts, owner, or pro-forma basis used for the project.
Actual degradation can vary by module technology, climate, mounting condition, maintenance, soiling recovery, weather exposure, workmanship, and monitoring method.
Year-25 output is a long-term planning comparison value and should be reviewed with product warranty language, measured data, maintenance records, and installer or manufacturer documentation.

Code and standard notes. Planning limits that should be checked before final equipment selection.

Use this chart as a production record; verify first-year kWh, NREL PVWatts or model date retrieved, documented degradation rate, manufacturer warranty language, measured production data, inverter replacement plan, cleaning and maintenance records, availability, storage dispatch assumptions, emissions factor basis, utility requirements, installer model, and owner review before relying on long-term production values.

How to use this chart

1Start from a documented production caseUse the first-year kWh already tied to resource source, tilt, azimuth, loss stack, performance ratio, date retrieved, and selected production scenario.

2Enter the degradation basisRecord the annual degradation rate, manufacturer or measured basis, climate note, mounting note, and whether the rate comes from product data, observed output, or a planning model.

3Route the long-term outputCarry year-N kWh, year-25 output, replacement notes, maintenance notes, and warranty-review notes into ROI, emissions, storage, or owner-review worksheets.

Worksheet checklist. Record source basis, review gaps, and assumptions before using the chart result.

Capture first-year baselineRecord first-year kWh, model source, date retrieved, loss-stack worksheet link, and selected production scenario before applying degradation.
Calculate year-N outputEnter the annual degradation rate and selected operating year, then calculate year-N kWh and percent of first-year output.
Document long-term review inputsAttach year-25 output, replacement plan, maintenance notes, monitoring basis, warranty-review note, and the worksheet that will reuse the value.

Common mistakes to avoid. Review these before turning chart current into an equipment decision.

Using first-year production in ROI, emissions, or storage work when the question is about a later operating year.
Treating one degradation rate as universal instead of recording the manufacturer, measured, installer, or owner planning basis.
Using year-25 output as a warranty decision without product warranty language, measured data, maintenance records, and manufacturer or installer documentation.

Frequently asked questions

These answers explain how to use the chart without turning a quick reference into a final design decision.

Can one degradation rate be used for every solar project?

No. Degradation depends on product, climate, mounting, maintenance, and measurement method. The worksheet keeps the rate user-entered and asks for the source or project basis beside the result.

Does year-25 output prove a warranty claim?

No. Year-25 output is a planning value. Warranty review depends on the actual product warranty, measured performance data, required maintenance records, and manufacturer or installer requirements.