Winter problem with gas water heater: gas line too small?

[Thatguy]

Check your gas meter with a clock to see how many cu. ft. per minute your heater is using, then convert to BTUs/hr [of power]. On my gas bill 6400 cu. ft. = 65 therms.

1 BTU [of energy] raises 1 pound of water 1 degree F and 50 gals weighs about 420 pounds.

15 minutes @ 2.5 GPM = 38 gals and if the shower water is 110 F only some of this is your 132 F water.

[hj]

Entering water in the wintertime is usually much cooler than in the summer, so that creates two problems.
1. As the water flows through the dip tube to the bottom of the tank it will have a greater cooling effect on the hot water at the top of the tank. And,,
2. Since the water is colder to start with it takes longer for it to be heated.
3. Both of these factors will cause the heater to NOT produce the quantity of hot water it does in the summertime.