  Disk accretion onto black holes is accompanied by collimated outflows (jets).
In active galactic nuclei (AGN), the kinetic energy flux of the jet may exceed
the bolometric luminosity of the disk a few orders of magnitude. This phenomena
can be explained in frameworks of so called "cold" disk accretion when the only
source of energy of AGN is the energy released at the accretion. The radiation
from the disk is suppressed because the wind from the disk carries out almost
all the angular momentum and the gravitational energy of the accreted material.
In this paper, we calculate an unavoidable radiation from the "cold" disk and
the ratio of the kinetic energy luminosity of the outflow to the bolometric
luminosity of the accretion disk around a super massive black hole in framework
of the paradigm of the optically thick alpha-disk of Shakura \& Sunyaev. The
ratio of the luminosities is defined predominantly by the ratio of the magnetic
field pressure inside the disk to the magnetic field pressure at the base of
the wind. The obtained equations applied to the jet of M87 demonstrate good
agreement with observations. In the case of Sgr A*, these equations allow us to
predict the kinetic energy flux from the disk around Galactic SMBH.
