We use a Solahart solar water heater which is made in Australia. It's a simple antifreeze thermosiphen system with a super-insulated tank just above the panel on the roof. For about 9 months out of the year it produces all the hot water we could ever use. The other three months we use an RV propane water heater. Back when I installed the solar water heater Oregon had a tax credit that paid for the unit minus about $50. One of the best investments I've ever made.
i own one...
and used it for over a year in my garage
it was the company from vermont...ccc or something like that
they are still available from home depot and/or lowes...where i got mine
but they are special order now
it is awesome
and let me tell ya
washing your car with hot water is the shiznizzler
i got the top unit with 3 elements
each element has individual temp setting
i believe water flow determines how many elements engage at a time.
the vermont company is especially good because they have a lifetime replacement on the elements to the best of my noggin