We had originally planned to install a Solar Thermal Hot Water system at our house (we love reducing our propane bill), but the the advancements in Solar PV, and Heat Pump Hot Water Heaters, have sent us down a different path. Adding Solar PV, grid-tie, or even off-grid, as well as a HPWH can be an economical solution, and more versatile. When Solar Thermal over produces your demand, you are left with only excess hot water, but when Solar PV over produces your demand the excess can be consumed by any load that requires electricity. Here are a couple of articles discussing the pros, and cons.
Solar PV Hot Water Article
http://www.homepower.com/articles/solar-water-heating/domestic-hot-water/heat-pump-water-heaters
Solar PV Hot Water Article
http://www.homepower.com/articles/solar-water-heating/domestic-hot-water/heat-pump-water-heaters