Joe, et al.
http://www.insinkerator.com/hwd.html
I'm in the planning and design stages of a syncro conversion that
involves installing a hot water on demand tap
same type as in home kitchens. my local home supply store has a small
version rated @500Watts (smallest i've found, most are 700Watts)
110volts. shouldn't be too much trouble to run off of my inverter.
with clever 'house' wiring I'lll have a switch to activeate the H2O
heater, and a double pole double throw switch to go from inverter to
street 110vts (along with appropriate pretty indicator lights).
Downside is these are designed for house hold water supply, and will
require a RV flo-jet pressure pump. possibly the westy/RV type is
sufficient I just haven't gone into the actuall testing phase yet.

I've used these in my house for some time.. and will wholly profess
their handiness for preparing instant food.. mashed potatoes, soups,
rice/pasta dishes and especially tea/coffe(french pressed), and COCOA..

they only heat a small amount at a time, and are insulated so they
don't run all that often if left alone.. hold heat for some time and I
don't expect any trouble with killing my 'house' battery while camping
unless I drink a lot of cocoa.

most 700watt ones go for $150+/- the 500watt one i'm looking at goes
for $125+/-
http://www.insinkerator.com/hwd.html

From:    Joe Federici <joefederici@EARTHLINK.NET>
Subject: Colman Hot-Water-On-Demand

I've been looking into adding a way to make or have hot water in my
van
and found most of the permeant add in systems are cheep or easy to
install and I'm wondering what others think of of the Colman hot water
on demand system. I've see it advertised on ebay in a kit containing
most of the popular accessories for around $140.00 plus shipping. That
said I wasn't sure how practical it is to carry around and set up
inside or outside the van.

I've read a few reviews and most people seem to be very happy with it.
One propane ball will heat proximally 40 gallons on water.