I have had really good experiences with solar showers. We used them continually when in back country camps doing projects and they worked very well. If for some reason, the water wasn't hot enough, it was no big deal to heat up some on the stove and enjoy. We always showered Navy style - quick rinse, stop the water, soap up, rinse off.

The 2 1/2 gallon model even gives you some "luxury time" once you have rinsed off the soap and grime. If necessary, I could get two showers out of a bag.