Solar Evacuated Tube Panels

[DanBoston]

I plan to have a contractor install a solar hot water system for my home. I know absolutely nothing about solar collectors. I just need to make sure that the evacuated tube solar panels that the contractor is recommending are good quality AND have a good warranty. He is recommending two evacuated tube panels made by Solar Panels Plus, LLC (Model # SPP-30A)

http://www.solarpanelsplus.com/solar-water-heaters/

Solar Panels Plus, LLC only offers a 10-year warranty on the tubes. Is that typical? I heard that some other manufatcurers offer 20-year warranties - but am not sure if that is for PV collectors?