I am in San Francisco area. My wife drives a Model X and I am thinking of selling my BMW 335 and get a CPO Model S. But one concern is if all our cars are EVs, what if electricity went out during a major disaster like an earthquake or war. Will it be more disaster-proof if we have both types of cars and choose whichever energy source (electricity vs gas) that is the most available in those hard times? That's why I am thinking of keeping the BMW as a backup car. What are your thoughts on this?