we've got a fridge and four freezers....asked my electrician husband about how long they would last on 5 gal of gas and he only guessed...lol....
we've got a wood stove downstairs and I did just order 300 8 hr tea lights....:)
FWIW if you’re just keeping your reefers cold you only need to run the gen for an hour a day assuming you can keep the doors mostly closed. Some years ago we kept the whole neighborhood cold, during hurricane EWA, by giving each neighbor an hour. An hour shouldn’t use more than a gallon so: 5 gal= 5days. We had the neighbors sharing their car gas since we were out for two weeks. I told them to save just enough car gas to get to a station when the station’s power came back on. Saved a lot of food for all of us.
The fridge and 4 freezers would last quite a while on the 5 gal. Once the motors are running the draw is low, and you need only run them for a short time to, especially in the freezer case, get them into the good zone.
Now, if you gotta open them every 5 min to see if the light is on... :-)