Agree, simple is best. I car camp in the back of my Tacoma for back country skiing and mountain biking and have one of the Zodi propane hot water heaters. I hate it. One speck of dust on the top of the propane tank and the gas valve gets clogged. Plus the thing is always trying to fall over and is just a pain to manage. I find myself now just falling back to my Nemo Helio pressure shower. For summer, just leave it in the sun and you are good. For winter, fill it halfway and add boil up a pot or two of hot water and you are good to go. Easy to manage and takes less time to heat the water than to setup the Zodi. Plus no batteries and pumps to manage.
Other people make a solar pressure shower out of weed sprayer and black paint from the hardware store.