While most of my off-grid articles have been about producing electricity, an area where you can make big energy savings on the cheap is using solar energy to heat water. It's not new, it doesn't have to be high tech and it works. Let's start with a quote from an article which appeared in Mother Earth News.

The first commercial solar water heater was patented in 1891; within five years, about 30 percent of the homes in Pasadena, California, had solar domestic hot water systems installed.

Although the solar hot water heating industry had spread to Florida by the 1930s, copper shortages during World War II (coupled with economic incentives offered by electric companies to switch to their hot water heaters) crippled the burgeoning solar hot water industry.

I remember a photo in (actually, probably on the cover of) Utne Reader a very long time ago showing 1930s rooftops in Pasadena, California. It clearly worked but it is also clear that heating water with free energy was not a good profit center for business.

In areas where there is no freeze danger, passive systems are easy to build. They are really no more than a tank in the sun. That tank could be as simple as a box with a metal sheet painted black in it and glass on top. A typical approach is to use the equivalent of a tank with float valve like that of a typical flush toilet to supply the water. Gravity is then used to deliver the hot water to where it is used.

Even if such a system was not your main water heater, it could easily supply hot water for a washing machine, for example. Or, for a total minimalist shower, add a roll of black plastic pipe tossed on your roof between the cold water supply and your shower.

Rather than try to tell you the whole story, I recommend you grab The Integral Passive Solar Water Heater Book, a free PDF download. It will tell you more than you ever wanted to know about passive solar water heaters including a lot of history that will probably surprise you.