Path-Q Solar

How should I value solar savings that continue after the system's financing ends?

Answer

Treat post-financing savings as future operating cash flows, not as immediate savings. Estimate the electricity costs avoided after the loan ends, then subtract expected maintenance, inverter or battery replacement, degradation, insurance changes, and other ownership costs. Discount those future amounts for uncertainty and time value of money.

Key points

  • Separate the financing period from the remaining useful operating period.
  • Use conservative assumptions for electricity-price changes, system production, degradation, and service costs.
  • Savings after financing ends can materially improve lifetime economics, especially when the system remains productive for many years.

What it depends on

  • Expected remaining system life and production degradation
  • Future electricity rates and bill structure
  • Maintenance, inverter, roof, and battery costs
  • Discount rate and the timing of cash flows

Risks and trade-offs

  • Long-term savings forecasts are sensitive to utility rates and system performance.
  • A system may produce less than expected or require major equipment replacement.
  • Using undiscounted lifetime savings can make the investment appear more valuable than it is in present-value terms.

Information you may need

  • System production estimate and degradation assumption
  • Financing schedule and end date
  • Expected equipment life and warranty coverage
  • A bill model showing avoided energy charges and unavoidable charges

Your next step

What to do next

Build a year-by-year cash-flow comparison that includes the financing period and the remaining expected operating life.

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