I know very little about this topic, including what the correct terminology
is. And, this is mostly just a curiosity question on my part.

But, I am curious as to what it roughly might cost for a typical gas station
to have an electrician install a mechanism where if the power goes out in
the neighborhood, a portable gas generator could be plugged in to the
electrical system to power the station and keep the lights and cash
registers on and pump gas to the public. I am not that interested in the
cost of the actual generators for this purpose -- just the cost to have the
electrical switch-over circuits installed and ready to be used if needed.

Why? -- because I am often amazed when there is a hurricane or other natural
disaster that knocks the power out in a region, and thousands of people need
gas to evacuate, plus emergency services vehicles need gas to operate during
the disaster -- but the gas stations with tens of thousands of gallons of
gas stored underground are all closed because they have no power to pump the
gas that they have.