What good is a gas mobile when there is no Gas? Or if the gas costs too much?
That problem has been little to none. Power outages are common.
Gasoline can be stored, and it is stored at many facilities all over the country. Electric power can't be stored - it has to be produced and consumed at the same time. The power grid doesn't have too many redundancies, and you can't quickly lay another 100 kV cable if existing connections are damaged. But it would take a pretty large disaster to destroy roads and prevent delivery of gasoline. The delivery truck can be easily rerouted, and you need only one usable road to supply a large territory.
Or if the gas costs too much?
At this phase of our civilization gasoline is generally cheaper than electric power, joule for joule. Some electric companies offer discount rates on nightly charging, but when it matters 1 kW*h of electric power costs 30 cents. One gallon of gasoline produces 36.6 kW*h, and today one kW*h of gasoline energy costs $3.80/36.6 = 10.4 cents. This would be a very low rate for the electric energy, even at night and at the lowest tier.
Also if the price of gasoline (and oil) starts climbing the other energy prices will follow soon.