Living in a rural California comminity for almost 20 years, I am no stranger to loosing power. On average I would loose power for about 65 days a year.. The worse was no power for 15 days in a row, but one time I had to evacuate for a month due to the CA wildfires and had to leave my animals behind.. although I was allowed to come back every few days to check on them..
In my experience in general the reptiles are fine at cooler temps for a period of time... their bodies just "pause" so no food since they can't digest. Maybe offer water by dripping some on the nose to see if they'll take it, but your dragon won't starve to death and if kept cool will not dehydrate as fast. Just keep them from getting below extreme temps like below 55. For an evacutation situation perhaps a tote with a clamp lamp on top that you can plug in at a hotel to warm him up a bit. Also just your car heater will keep them from getting too cold.. but in LA..probably not as much a concern compaired to someone in Alaska.
At home if being without power for over 3-4 days is a reality for you then having a generator is going to be best (It can run your fridge too and keep your food from spoiling!) But these can work nicly too...
The Solar Generator 1000 converts sun rays into portable power for home & outdoor use. It consists of Explorer 1000 + 2 x SolarSaga 100W. Ideal for versatility.
www.jackery.com
And for extra you can hook solar panels up to them too to extend run time.
Another alternative is to use your car as a generator.. you can get one of these DC to AC power converters..
You just hook it up to your car battery and then let your car idle or else you get dead battery. Run a long extention into the house to power stuff that way. Some of them do up to 1000W which gives you a lot of options.