I recommend a dual power (110V/propane) Suburban with DSI. They run about $500 ($150 more than just propane). If you run a propane heater, you will really appreciate the dual power. When it is REALLY cold, our little electric heater doesn't seem to be quite enough to keep things toasty. The main heater has to kick in from time to time to help the electric along, so anything I can do to conserve propane is a plus.
If nothing else, why not use someone else's power (you are paying for the connection already) to heat your water?
Jose