HVAC would be a closer analogy, although even that probably has more labor involved over a 20-year period that solar promises.  Furnaces and A/C do need maintenance every few years. 

A better analogy is probably roofing itself.  That's pretty comparable both in lifespan and for the "almost no maintenance needed" life.  

In fact, the two may also coincide in other ways.  When you need a new roof, you're also probably gonna have to pay solar array uninstall/reinstall too (sitting on top of the shingles), which may just prompt full replacement at the same time (depending on age).