  In a recent article Garc\'ia-Pintos et al. [Rev. Lett. 125, 040601 (2020)]
studied the connection between the charging power of a quantum battery and the
fluctuations of a "free energy operator" that characterizes the maximum
extractable work of the battery. The authors claimed that for a battery to have
a nonzero charging power there must exist fluctuations of the free energy
operator, and the fluctuations upper bound the charging power of the battery.
In this Comment, we point out that the analysis contains several misconceptions
that call into question the validity of the results and conclusions.
