I'm not too terribly worried about my aquarium at least. At 125 gallons that's a lot of water to maintain temperature for a while. Can wrap it up with towels for sure but even a few days shouldn't cause immediate issues.
If anything I'm grateful that I didn't get new fish as I had originally planned last weekend due to snafus, as it would've been a sizable number of them in a little 10 gallon quarantine tank. A power outage for any considerable length of time in such conditions would've been disastrous.