Answer: -The best Pennsic water heater is a pot and a fire (real low tech, but in keeping with the atmosphere.) If you want the 20th C. comforts of home, stay home. -For ANYONE wanting hot showers at Pensic. Solar hot water bags are low tech, Take up little or no space for packing and,(with a halfway sunny day) get REAL HOT. Basicly, if the sun was out long enough to make you sweat, It was out long enough to get your shower water hot. If it was a long sunny day, you may have to add cool water to the bag to prevent scalding. Make sure to place the bag where it will be in the sun most of the day. Check on it once or twice a day to make sure the tent shadows haven't covered it. Take your showers just before sunset, when the water is hot and the ambiant air in your shower stall is tolerable. Run enough water to wet your surfaces then close it off. Soap up, then rinse off. My lord and I can BOTH take wonderful CLEAN HOT showers from a 5gal bag. (admittedly, I do not have long hair) WARNING: when you build your own shower stall, build STURDY. 5gal bags of water are not light! A simple pully system will get the bag up high enough to wash your hair without causing a hernia. Or... get ready to stand in line for tepid showers, or shower at 3am.