Path-Q Solar

Does panel degradation change the size of system I should install?

Answer

Yes, it can affect sizing, especially when the system is expected to meet a long-term energy target. A designer can model expected degradation and decide whether modest initial oversizing, subject to site and equipment limits, is appropriate; degradation should not be used to compensate for uncertain load estimates or poor design.

Key points

  • Size the system using expected future consumption and the desired performance over the ownership period.
  • The panel's warranted degradation curve is an important design input.
  • Inverter limits, roof area, interconnection rules, shading, and export constraints may limit oversizing.

What it depends on

  • Future electricity use and desired offset
  • Ownership period and degradation specification
  • Roof layout, shading, orientation, and available capacity
  • Inverter design and applicable interconnection requirements

Risks and trade-offs

  • Oversizing can increase upfront cost without producing useful value if exports are restricted or compensation is low.
  • Undersizing may leave the system below the desired output later.
  • A larger system does not solve poor roof conditions or inaccurate consumption forecasts.

Information you may need

  • Current and expected future electricity consumption
  • Panel and inverter specifications
  • Design-life assumptions and any export or interconnection limits

Your next step

What to do next

Ask bidders to show projected first-year and end-of-horizon production, including degradation assumptions and the reason for the proposed system size.

Path-Q

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SQ00846