The extreme cold in my area also presents another hazard to the tankless heat exchanger. Absent careful dampers, you can have cold air come down the vent pipe and freeze the heat exchanger during a period of non-use. That ruins the device and exposes you to a flood as well. Too many down sides to the technology in my area. It would have been fine in San Diego.
BTW, I'm approaching 14,000 miles on the Harley that I purchased last June with 7507 on the odometer. The 60 mile round trip to work each day is more enjoyable and affordable on the bike. A new tire went on the back at 13,000 miles. The Versys sits in the garage at home with 9500 miles on the odometer.
We did have ours freeze up once (-17 in 2003, I believe), but no internal damage to the unit or pipes, for that matter. I didn’t install the little thermostatically-controlled electric resistance heater for the unit so I was lucky. Since then I improved the insulation and installed a little fan to blow warm air from the adjoining room on it when needed, but it has never been nearly that cold again.