Path-Q Solar

How should expected panel degradation be included in a solar payback calculation?

Answer

Reduce the modeled energy production gradually over time using a defensible degradation assumption, then calculate each year's avoided-cost and export revenue from that lower output. Include the same assumption consistently across production, savings, warranties, and any replacement analysis rather than subtracting a one-time amount.

Key points

  • Year-one output and later-year degradation may be modeled separately if supported by the panel documentation.
  • Use annual cash flows so the effect of lower future production is visible.
  • Test the result with conservative and optimistic degradation cases.
  • Do not treat a performance warranty as a guarantee of a specific payback period.

What it depends on

  • Panel technology and documented performance assumptions
  • Initial production estimate and system losses
  • Electricity rates and export value over time
  • Analysis period and discount rate

Risks and trade-offs

  • Lower future output lengthens payback and reduces long-term return.
  • Using a generic degradation rate may not reflect the selected equipment or operating environment.
  • Other failures, downtime, and soiling may matter as much as gradual degradation.

Information you may need

  • Panel performance documentation
  • Year-by-year production model
  • Savings assumptions and analysis period
  • Sensitivity cases for degradation and downtime

Your next step

What to do next

Ask for a year-by-year cash-flow model that separately identifies degradation, downtime, maintenance, and rate assumptions.

Path-Q

Find the right next step

Answer a few questions and we’ll narrow your options.

Loading…

SQ01186