In my case, it's difficult for me to store a generator. When the one I had for Frances/Jean/Wilma finally rotted, I bought an inverter instead. VERY storable, and traveled with me when we evacuated. Enough power to run the pumps in both tanks. Lights off for a few days no big deal, I just brought them back over a few days. I also had an air conditioned place to sleep (my car), it was quieter than a generator, and only used a little over a quarter tank in 24 hours. Hopefully no long term car problems, but I'll get an oil change anyway.
Once running, tanks were good, except they were off for about 50 hours before I could make it back. RIP 6 fish, 2 damaged acros/birds nest, and maybe lost a new small plate, but 5 fish made it with plenty of other corals.