I've got a couple of batteries that I keep charged (one gel cell, one marine) for emergency power, but they aren't going to last long enough for a week's power outage (I'm in the San Francisco Bay Area, and in a major earthquake, I'd expect power to be out longer than a week). The issue of gasoline going bad and diesel generators "wet stacking" has kept me from considering buying one.

Nobody here has mentioned propane powered generators; why is that? The fuel won't go bad, can be used for cooking and heating, and so on. Are propane powered generators just not ubiquitous enough for consideration or are there problems?