Comment by tedsanders

Electrons lose their energy to other things.

Here's one quick explanation why:

If electrons lost their momentum and energy only to other electrons, then in aggregate, electrons would keep their momentum and energy. Since electrons do not permanently keep their momentum and energy in normal conductors, they therefore must lose momentum and energy to non-electrons.

Also, if you look at the Wikipedia link on the comment that says claims electrons lose energy to electrons, you'll see that Wikipedia says electrons lose energy to ions, not electrons.

(Also, as a condensed matter physicist, I always feel a little dirty/inaccurate saying that electrons carry charge currents. I prefer the vaguer charge carrier, because charge carrier can refer to an ensemble of electrons.)