Using the sun to heat water is cheap and relatively easy.
I live in a very sunny spot of the globe where a simple solar collector heats my water.
On top of the house I have a 100 meter roll of flexible, black half-inch pipe. This is hooked up to the water reservoir, which is higher than the roof. The water flows down the black pipe and into a conventional water heater that is not turned on. The sun heats the water and the insulated tank keeps it hot all night.
We have free heat for the water 99 percent of the year. The whole setup cost me about $50 eight years ago and should last another two years.
San Francisco del Rincon, Mexico
Most hot water is not used for drinking or cooking. But if you try this project, and you intend to drink or cook with the water, be sure that you use a black plastic that is rated safe for potable water. To read more about do-it-yourself solar water heaters, go to www.MotherEarthNews.comand search the Archive for “solar water heaters.”— Mother