Having lived through Hurricane Sandy in NYC: don't assume you can get gas to fill your generator in a disaster situation. Solar panels paired with a battery aren't dependent on a supply chain (that itself needs energy).
Yes, getting energy from a sustainable source of energy is the best way, but assuming you only use it for power outages once or twice a year, I am not sure it is worth the investment. Especially if you expect it to last a day/few days (if you are self sufficient for a few days you'd better do it all year long).
