Solar water heaters are among the easiest renewable technologies available. It is literally as simple as a container for the water that is painted black. For

Solar water heaters are among the easiest renewable technologies available. It is literally as simple as a container for the water that is painted black. For something done professionally it is trivial to have a hot loop that keeps a well-insulated storage tank at temp. With a bit of effort you can even reclaim some of the heat from the shower waste water.