I was involved in a North Slope oil project where we were adding a processing station at the limits of the existing network. We obtained the electricity from a powerline but because operators and maintenance crew could be isolated working there and in the event of a powerfailure, we had to have 'spare' power available so there would be preservation of life support (including a watersource and bathroom). I ordered several tons of batteries for the UPS (Uninterruptible Power) portion in addition to an independent generator. Fun job.

I have electrician friends who have provided their houses with a generator they can use if power goes out in the city. Useful for potential earthquakes.