Power Outage - lessons learned

We lost power for 12 hours today. We learned that we need a backup plan beyond the fire place for heat and power but we also learned that on a sunny day, the temperature in our house is 54 degrees - not bad, lending credence to the strategy of south facing buildings with lots of glass on the south side. I plan to undertake a BTU/sq. ft. calculation to determine how our performs versus other houses.