Solar systems usually come with several separate warranties, and they don't all cover the same things. There is often a product warranty on the panels, a performance warranty on how much output they keep over time, a separate warranty on the inverter, and a workmanship warranty from the installer.

Read the length of each one and what it excludes. Inverters often need replacement sooner than panels, so find out how long that coverage runs. The workmanship warranty matters too, because it is what covers leaks, wiring problems or installation mistakes rather than defects in the equipment.

Finally, think about who will honor these promises years from now. A warranty from a company that goes out of business may be hard to use. Ask how long the installer has been operating, whether manufacturer warranties remain valid if the installer closes, and whether labor for removal and reinstallation is included in a claim.