If you can pump gas you can run a generator, which means you can turn gasoline into electricity. That means you can "fill" your "green" car during a power outage. Many consumer generators can also run on propane or natural gas, which means you have two other fuel sources in a power outage. If you have solar panels on your home you can "fill" your "green" car during a power outage. If you have a home backup battery you can "fill" your "green" car during a power outage. There are zero scenarios where a car that can be fueled by multiple fuels is *less* flexible than a car that can only be fueled by one.