Sorry to be 2 days behind the thread.
   I installed a Flex-a-Lite heater from JEGS to handle our Chicago cold.  See _http://www.jegs.com/i/Flex-a-lite/400/640/10002/-1_, for $160. I bought it when on sale for less.  Fits nicely under the panel in an RV-10.  Both a shutoff valve on the supply side, and a one-way backflow preventer on the return line are recommended.
   Sorry I didn't weigh it before installation, but it felt like it was less than 10 pounds total when handling it.

Phil
RV-10 w/20B in Chicago area (wiring and accessorizing the engine....forever)