Will new solar panels last 25 years? Most of stuff on the outside on my house doesn't have a lifespan that long. You could end up paying off the loan after the panels have stopped working.
Most are warranteed at a particular percentage of nameplate capacity (95%+) at delivery and then in a straight-line decay after a certain point out to a certain level (75-80%) at 25 years.
http://us.sunpower.com/sites/sunpower/files/media-library/wa... [edit: better link], for example. that is 95% through year 5, then .4% linearly through year 25, or 87% of nameplate at year 25. They are a premium vendor, but the warantee structure is fairly standard across legitimate vendors.
