  In this paper, the Penrose process is being used to extract rotational energy
from regular black holes. Initially, we consider the rotating Simpson-Visser
regular spacetime which describes the class of geometries of the Kerr black
hole's mimickers. The Penrose process is then studied through conformally
transformed rotating singular and regular black hole solutions. These both
Simpson-Visser and conformally transformed geometries depend on mass, spin, and
an additional regularisation parameter $l$. In both cases, we investigate how
the spin and regularisation parameter $l$ affects the configuration of an
ergoregion and event horizons. Surprisingly, we find that the energy extraction
efficiency from the event horizon surface is not dependent on the
regularisation parameter $l$ in the Simpson-Visser regular spacetimes and hence
it does not vary from the Kerr black hole case. While, in the conformally
transformed singular and regular black holes, we obtain the efficiency rate of
extracted energies are extremely high compared to the Kerr black hole scenario.
This distinct signature of the conformally transformed singular and regular
black holes would be useful to distinguish them from the Kerr black hole in
observation.
