How old’s your roof? Just wait until it’s time for new panels. You’ll want new panels after a couple decades and change for the significantly improved performance. Panel work will be routine for roofers in the 2030s and 2040s. If you installed them on an old roof, you made a mistake, and your municipality probably shouldn’t have approved the work in the first place.

Your replacement inverter should only cost $1-3k in present money, depending on its size. You probably have a warranty on it for the first half of your panels’ life.

You also don’t need to pay for an expensive extensive cleaning unless something goes really wrong or you live under an HOA that is hostile to solar.

By far, the biggest factor in ROI is your generation relative to your initial installation cost minus tax credits and SRECs.