My Boler came with a typical propane-fired 6-gallon RV water heater (an American Appliance model), so I have a heater but didn't add it.. Since it needs a big flat hole in the curved trailer wall, I wouldn't want to take on retrofitting one unless is went in the "factory" location, although someone with more energy than I have did a really nice custom installation job and reported it here many months ago.
Given the installation issues of a propane-fired heater, for use only with external power service the convenience of an electric heater is appealing. Trailer electrical capacity would need to be considered, as the heater itself might need 15 amps at 120V to be useful.
QUOTE (Sandra Lair @ Apr 3 2007, 11:45 AM)

...We tried one of those devices that is supposed to heat the water up as it goes through the line, but it didn't really work. The most we ever got was a barely noticeable change from cold to lukewarm.
Heating capacity for a "demand" or "instantaneous" heater is a raw power issue: water flow rate multiplied by temperature rise determines the power required, so you can assess the approximate ability of an electric water heater to meet your needs by how many watts it uses. Sandra, do you remember the power (or current) rating of the inline heater which you tried?