Never thought about solar water heating before. Hmm. My house currently has two 50-gallon gas fired heaters, connected in series. Needless to say, if the upstream one fails first, I'm effectively down to one 50-gallon heater. If the downstream one fails first, then I'm hosed.

My "I'll deal with it when it's a problem" plan has always been to replace both tanks with a single tankless system. But we get plenty of sunlight here in Houston. We're not as far south as Mexico, but still... I hadn't given any serious thought to a solar heater. My roof is now mostly covered with solar panels (*sigh*) but there's certainly still room up there to shoehorn in one of these things. (Fun, fun: Google's satellite imagery now includes my solar system, so the pictures are less than a year old.)

So... pros and cons of going gas-fired-tankless vs. solar-heated-water-tank?