I have never had difficulty buying anything with cash during a extended power outage. As long as I had anywhere close to the correct amount of cash, the sale was completed.
I was in a state that had a major ice storm. The government sent electric companies to help with the repairs from all over the United States. Areas were down for over two weeks and yet I had no cash nor any problem whatsoever purchasing, gas, food, and other products. As long as there way power, by way of generator for example, they took credit or debit cards. They batched the information and sent it when they could.
If there was no power and they were not on a generator, they simply were not open.
I guess I’ll eat my words when they drop the nuke on us and the emp kills all electronics.