I’m skeptical about solar water heaters. It’s still something like $5K not including labor, and it only reduces the part of the bill that is spent to heat water (in my house that’s 10% to 20% of total bill, depending on the season, I think.) On the other hand, solar panels offset lighting, computer, TV, and, most important of all, air conditioning.

Solar water heaters make most sense for people with heated pools.