The Canadian Clarity's battery warmer (which works only when the car is plugged in) doesn't kick in until the battery is fully charged. If you set the built-in charge timer in your U.S. Clarity so that charging completes just before you plan to start your drive, the battery will be just as warm as a Canadian battery before the battery warmer comes on to maintain the temperature achieved through charging. I'll admit I'm guessing that the battery warmer only maintains the charging temperature, but because the battery warmer doesn't kick in until after charging, I'm assuming the warmth generated through charging is sufficient to cope with -22F. At -23F, I'm not so confident.