I mean, if you were me… and trying to decide how to heat your hot water… what would you do?
I mean… solar yes. But in MA they** say you can only get to a 60% solar fraction. Should I believe them? I say no. Gary at builditsolar.com gets 95%+ in MT. OK, so how does one do that! Most people claim you shouldn’t do drainback, but I’ve been reading, and Tom Lane’s excellent guide to solar hot water systems says they are actually the way to go. So that’s that. We’re doing it. (Now to find someone to actually do it.)
**they as in… Google around, and you will find it’s quite typical. But I think this is partially because people 1) use non-drainback systems and 2) design such systems to provide ~60% (undersized, not a steep angle for keeping up in the winter and reducing temps in the summer, etc).