Depends how long the electricity stays out.

As long as phones are charged bitcoin still works.

However, the moment that power goes out you can not use cash or debit anymore because all the ATMs and cash registers require electricity and internet connection to work.

I seen this first hand, my town had no electricity for 3 days.

When the power did come back on the police were standing guard outside Coles so that they could dump all the food that they were refusing to sell into the dumpsters.

One shop in my town was open and accepting cash.

You could not even buy fuel because all the servos neglect their backup diesel generators (if they even still have them half of them don't even have backup power anymore)

Fortunately the hospital has backup diesel generators and enough diesel stored to run them for a week but no one else seems prepared for a grid down, especially shops.

You could still spend Bitcoin (online unfortunately no one in my town accepts it)

But apart from that one shop(which was only open for the first day of the power out and closed once their refrigerators were empty)and the drug dealers obviously, cash became absolutely worthless for 3 days when we had no electricity.

So in conclusion grid down makes it harder to spend cash than Bitcoin