> It’s too bad solar degrades over time... without it losing its efficiency over a 15 year period.

Google says they degrade to 80-90% capacity over 25-30 years, which is ~double your 15 year time period. I've also previously seen people claiming that they then stabilise around the 80% level, and that we don't really know how long their total possible lifespan is because many extant solar panels are outliving their 25 year rated lifespans.

Capacity reduced to 80% won't work for some high-performance use cases, but is pretty decent for most.