  We derive here the expression for the accretion luminosity, $L(\infty)$, as
seen by a distant inertial observer $S_\infty$, for the case of spherical
accretion onto a static compact object having a surface gravitational red-shift
$z_x$. It is found that the ``efficiency'' for conversion of mass energy into
accretion energy is given by $\epsilon = z_x/(1+z_x)$. And since the maximum
value of $z_x$ permitted by General Theory of Relativity (GTR) is 2, the
maximum theoretical value of the accretion efficiency is 66.66%.
