  We provide a semi-analytic comparison between the Blandford-Znajek (BZ) and
the magnetic reconnection power for accreting black holes in the curved
spacetime of a rotating black hole. Our main result is that for a realistic
range of astrophysical parameters, the reconnection power may compete with the
BZ power. The field lines anchored close to or on the black hole usually evolve
to open field lines in general relativistic magnetohydrodynamic (GRMHD)
simulations. The BZ power is dependent on the black hole spin while magnetic
reconnection power is independent of it for the force-free magnetic
configuration with open field lines adopted in our theoretical study. This has
obvious consequences for the time evolution of such systems particularly in the
context of black hole X-ray binary state transitions. Our results provide
analytical justification of the results obtained in GRMHD simulations.
