I makes sense, but its also a bit disappointing.

I basically expect the heater to work this season if it is installed this season. My concern is whether it works during next season (after a season of use and then a half year of sitting around doing nothing). If I'm not wrong, it sounds like I'd be in the same boat next season whether I buy the unit myself or he supplies it. So the $500 difference is me paying up front for a problem occurring this season which I feel has a slim chance of happening.