In semiconductor physics, how can we know which units to use for Boltzmann's constant?
As I said in the comments, I hate that they don't teach you how to properly handle units in schools...
You know how 1 kJ is 1000 J, or 1 foot is 12 inches? in the same way, 1 J is 6.242·10¹⁸ eV, and 1 eV is 1.602·10⁻¹⁹ (= 1/6.242·10¹⁸) J. The fact that you can convert one to another means they measure the same dimension, but the fact that they aren't equal, that that conversion factor isn't 1, says that they're different units.