If I maybe add always have a sponge filter thats already cycled because a new sponge filter will do nothing much but aeration in a power outage. In my big tank I have a big sump and on top of that two sponge filters inside the tank. Reason being is that if I lose power and I'm at work or away it will automatically kick in. Heat is not an issue with me I once forgot to plug in my heater after cleaning my sump and temps dropped to 72 from 80.A good sized canister filter consumes maybe 60watts. Air pumps are typically less than 10watts. Heaters would be a BIG load on a battery backup power source if you've got 200w units, etc..
Main thing with long term power outages is preserving your bio media in your canisters or HOB filters. I'd remove it from your HOB and place it in your tank. Same with a canister if the power outage is going to exceed 10-12hrs. If you don't, you are going to have one heck of a stinky anaerobic mess in your canister.
Sponge bubblers are king in this situation. You can run them with battery powered air pumps, or just leave them sit in your tank.
Many fish are hardy but if were talking about a few days without electricity and it happens frequently just get a gas powered generator for your family and your fish lol