Sun energy is a natural and free source of energy that we use without paying for any penny. But due to the fact of it's availability also do we make any use of it. And even the invention of the various sources of heating water, people of the old age would use the sun energy to warm their bathing water. I frequently use it when I'm not in hurry though it takes a lot of time to warm. How about you guys do you prefer the sun energy to warm your bathing water and if so how often?