  The evolution of white dwarfs is a cooling process that depends on the energy
stored in the core and on the way in which it is transferred through the
envelope. In this paper we show that despite some (erroneous) claims, the
redistribution of chemical elements ensuing the crystallization of C/O white
dwarfs provides between the 10% and the 20% of the total energy released during
the crystallization process, depending on the internal chemical composition,
which is not negligible at all, given the present state of the art of the white
dwarf cooling theory.
