  We use Monte Carlo approach to study the energetics of electrons accelerated
in a pulsar polar gap. As energy-loss mechanisms we consider magnetic Compton
scattering of thermal X-ray photons and curvature radiation. The results are
compared with previous calculations which assumed that changes of electron
energy occurred smoothly according to approximations for the average energy
loss rate due to the Compton scattering. We confirm a general dependence of
efficiency of electron energy losses due to inverse Compton mechanism on the
temperature and size of a thermal polar cap and on the pulsar magnetic field.
However, we show that trajectories of electrons in energy-altitude space as
calculated in the smooth way do not always coincide with averaged Monte Carlo
behaviour. In particular, for pulsars with high magnetic field strength
($B_{pc} > 3\times 10^{12}$ G) and low thermal polar cap temperatures ($T <
5\times 10^6$ K) final electron Lorentz factors computed with the two methods
may differ by a few orders of magnitude. We discuss consequences for particular
objects with identified thermal X-ray spectral components like Geminga, Vela,
and PSR B1055-52.
