Path-Q Solar

How should inverter replacement risk be reflected in a long-term solar ROI estimate?

Answer

Include a reserve or scheduled future cash outflow for likely inverter replacement, using a range of timing and cost assumptions rather than assuming the original inverter lasts for the entire analysis period. Discount the future cost to present value and account for possible downtime.

Key points

  • Identify the inverter type, warranty period, service terms, and expected replacement timing.
  • Model replacement cost, labor, related equipment, disposal, and any permitting or service work.
  • Include lost production or bill savings during an outage if replacement is not immediate.
  • Test early, expected, and late replacement cases.

What it depends on

  • Inverter technology and equipment specifications
  • Warranty and service coverage
  • Analysis period and discount rate
  • Replacement cost and downtime assumptions

Risks and trade-offs

  • Ignoring replacement can overstate long-term ROI and understated lifecycle cost.
  • Including an overly conservative replacement cost can make a sound project appear less attractive.
  • A replacement may provide improved functionality but can require compatibility with older panels or controls.

Information you may need

  • Inverter model and warranty
  • Proposal's lifecycle and maintenance assumptions
  • Replacement cost estimate
  • Expected production loss during service

Your next step

What to do next

Add discounted replacement cash flows to the ROI model under early, expected, and late timing cases, and request a serviceability and warranty review.

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SQ02704