Here is my solar water heater on the roof which helped me to get my lowest electric bill ever - just $37 in May 2003:
I ordered it as a kit from Solar Roofs. I installed it by myself in one weekend. Al Rich was nice enough to answer all the questions that I asked him before I bought it. It came with a well-written installation manual which can also be downloaded from his site. It paid for itself in less than three years.
5726 people have wanted free hot water.