Maybe you are supposed to figure out how to have a power reserve. Your life or someone else's life may depend upon it. I remember when my mother was in Hospice care and she had a hospital bed at the house. We had a lightning storm that took out the power for many hours. We found out that her bed was inflatable, and that it had a slow leak that was pumped back up continuously by a pump. Then I began to consider how to use my car as a generator for power.
Now I have a 1400 watt inverter in my Prius and the last time that power went out I had figured out how to let the prius idle with the emergency brake on (so the lights won't come on) so that the car keeps the 12 volt battery powered up. I was able to keep the refrigerator running for three days when we had a flood where I was visiting. It takes strong jumper cables connecting to the battery. We didn't have a way figured out for running the water pump though.
I like backup systems that use batteries as the power store. Where AC gets created constantly from the battery systems. These are called on-line ups.
RE: DIY Off Grid PowerWall Update: Used Electric Car Lithium Ion Batteries, Arrived!