  Buchdahl star is the most compact object without an event horizon and is an
excellent candidate for a black hole mimicker. Unlike black holes, rotating
Buchdahl star can be over-extremal with respect to the black hole, sustaining a
larger spin. We show that it can also develop an ergosphere above the threshold
spin $\beta > 1/\sqrt{2}$, which allows extraction of its rotational energy.
Electromagnetic field around Buchdahl star is also expected to differ from that
of black hole in both strength and topology. In this paper, we explore the
energetics of Buchdahl star focusing on the magnetic Penrose process in the two
magnetic field configurations, i.e., uniform and dipole. Below the threshold
spin, Buchdahl star is expected to be quiet, while above the threshold it can
be much more efficient than the black hole if a dipolar magnetic field is
developed on its surface.
