Path-Q Solar
How can panel degradation affect the payback estimate for a solar system?
Answer
Degradation usually lengthens payback slightly because annual energy savings decline over time, but the size of the effect depends on the degradation rate, upfront cost, electricity-value assumptions, financing, and how much of the system's value occurs in early years.
Key points
- Use year-by-year production rather than a constant annual output in the payback model.
- Test multiple degradation assumptions and include inverter replacement, maintenance, financing, and other ownership costs.
- Separate simple payback from discounted cash flow or other returns that account for timing and risk.
- Compare degradation effects with larger uncertainties such as future electricity prices, export value, and actual consumption.
What it depends on
- Initial system cost and financing
- Panel and inverter degradation assumptions
- Electricity prices, bill structure, and export treatment
- Actual production and consumption profile
Risks and trade-offs
- A simple payback calculation may omit financing costs, replacement costs, and the time value of money.
- A longer payback can result from changing bill assumptions rather than physical degradation.
- Higher production in early years may partly offset later output decline.
Information you may need
- Full cash-flow model and financing terms
- Production estimate by year under several degradation cases
- Maintenance and replacement assumptions
- Bill and export-value scenarios
Your next step
What to do next
Ask for a year-by-year cash-flow comparison with and without degradation and review which assumptions cause the largest change in payback.
Path-Q
Find the right next step
Answer a few questions and we’ll narrow your options.
Loading…
SQ00406