If there is no AC, and you are exerting yourself a lot (no car or transportation is down, more work to prepare food, even having to take a dump outside), 5 gallons is barely enough for one person to drink per day. You'll be sweating a lot more in those conditions.
Another example is food in winter months. During a disaster, even with winter gear, your houee may not be heated. If it is -20C inside, your body will need more calories.
If you're having to go outside to cook, to expel waste, and maybe even to go find snow to melt for water, you're going to need 3x your caloric intake.
You have to plan for worst case usage per day, not best.
> 5 gallons is barely enough for one person to drink per day.
OK, no. If you're running a marathon, in hot weather, you're at maybe a liter per hour. Unless you plan to run 20h marathons and the sun never sets, 5 gallon is well beyond drinking needs.
And unless you're able to exert yourself at that level at all, this isn't the "worst case", this is pure fantasy.
And if you're preparing for -20C in your house, I recommend investing in insulation, not more calories stored away. (I also question 3x, the figures I've seen point to 2x, with exertion somewhat counteracting cold)
If you drink ~19 litres (5 US gallons?) of water every day you will not survive long. That’s about an order of magnitude more than is recommended under normal non-strenuous conditions.
I drink may be two liters of water per day. Unless Google lies to me, 5 gallons is almost 20 liters which would be enough for 3 weeks for me with rationing.
Another example is food in winter months. During a disaster, even with winter gear, your houee may not be heated. If it is -20C inside, your body will need more calories.
If you're having to go outside to cook, to expel waste, and maybe even to go find snow to melt for water, you're going to need 3x your caloric intake.
You have to plan for worst case usage per day, not best.