Why We Shouldn't Use These Technologies?

I live in the south here we don't grow apples. Apple trees are easy to plant. Just plant em out in the street and go out and pick some. Why do we not use the energy that's raining on the house all day long to heat our water? I'm coming at it from thep perspective of dollars and cents. One of my projects is i would like to build a solar hot water heater in my home. But i haven't done it yet,. so this is not coming, but i know i've seen the technology s so duable.