Solar water heater is basically capturing water in a vessel and letting the sun heat it. It's still going to need either electricity or gas to get it up to a temperature where it's going to give you a shower or be able to deliver enough hot water to wash your dishes. The point is that it's going to take water from a ground temperature of 45 and raise it to 70 degrees basically for free. Which means that you only have to achieve another 50 to 55 degrees to get it really hot for a shower. That's an advantage because you're only raising the water 50 degrees as opposed to 100 degrees. So you save some money with solar water.