  We present a first attempt to derive the cosmological evolution of the
kinetic luminosity function of AGN based on the joint evolution of the flat
spectrum radio and hard X-ray selected AGN luminosity functions. An empirical
correlation between jet power and radio core luminosity is found, which is
consistent with the theoretical assumption that, below a certain Eddington
ratio, SMBH accrete in a radiatively inefficient way, while most of the energy
output is in the form of kinetic energy. We show how the redshift evolution of
the kinetic power density from such a low-mdot mode of accretion makes it a
good candidate to explain the so-called ``radio mode'' of AGN feedback as
postulated in many galaxy formation schemes.
