The dealers here are saying that you can get up to $2000 back from the federal govt on a solar water system, supposedly all their customers are getting it. Which leaves my cost somewhere around 4 - 5000.
Sunda and apricus are the 2 brands I'm seeing here in PA. I agree, the numbers dont pencil out. I figure my water heating costs are about $600/year, and since they tell me I'll save 75% of that I figure it'll be closer to 50%. So I'd be investing $5000 to save $300 per year ... not a very good move financially.
When I built my house I insulated under and around the basement floor and put pex tubing into the slab - so my basement floor could be one huge heat sink. My intention is to put in solar for hot water, and also use it to heat the basement floor, letting it radiate into the house all night. Unfortunately, now I'm finding out that I'll only get about 35000 btu's/day total out of the solar, so not much at all will be left to go into the floor after the water is hot.
My conclusion: not worth it. Unless I can save an awful lot by doing it myself.