I've lived a couple places without hot water (well, one place they only turned it on Sundays), so I don't take it for granted. Never could take a cold shower, even in hot weather.
It's almost criminal to build a new house without a solar water heater. Everywhere the sun shines enough to heat water (except here in Oregon for the past month). The technology is proven and not very expensive.
There are plenty of places to read up on it, just google solar water heater. Build it Solar
is a good one; they have some free pdf HomePower articles. Grab them while you can.
In the hotter climates where it doesn't freeze, solar water heating is very simple. Where you have freezing temperatures, you will either have to drain the water from the collector when temperatures approach freezing (this can be done automatically) or use a type of heat exchange system, where anti-freeze is circulated but kept separate from the household water.
Update: Another good site
for Solar Water heating and other solar info.