People, heat, refrigerator, water pump (if applicable) and then hot tub, in that order for power outages during xtreme freezing weather 15-20f and colder. How many power outages have you had in your area when it's been that cold? How long has the power been off during these extreme cold weather outages? Arm yourself with that information first before you decide if it's a serious problem now or possibly in the future when tub failure becomes more likely. If it is create a contingency plan. Hot Tub ownership in cold climates 101.
