Water heater with no water pressure?

I'll be moving into a yurt within the year and while I have damned near everything figured out...hot water eludes me. Yes, I have a wood stove and heating water on it works, but I'm talking about a nice shower, you know? I already use those camping black bags that heat water by the sun, but it doesn't work too well out here in the Northwest. I've been looking at propane heaters, but they require water pressure, which I don't have at the moment. I collect rain water and am no where near city utilities. The most luxurious thing I have is three solar panels to work my computer equipment ;) Any thoughts on a way to heat mass amounts of water? I live in Washington State...I HAVE water.