Looking at Rheem water heater specs, I noticed some strange numbers. Two
of their water heaters have all the same specs except for the warranty and
the cost per year. The cost per year of one is $309 and the other is $231.
Everything else is the same, including first hour rating, tank size, input
btu/h, recovery rating, dimensions, weight, and energy factor.

I thought you could calculate the cost per year from the first hour rating,
the btu/h input, the recovery rating, and the energy factor. But if all
four of those are the same, how are they getting such different costs per
year for them?

22V40F1, $309/year:
http://waterheating.rheem.com/conten...csheets/Reside
ntial%20Gas/RHGasFury.pdf

22V40 PROF, $231/year:
http://waterheating.rheem.com/conten...csheets/Reside
ntial%20Gas/RHGasPro.pdf