  The instantaneous contributions to the 3PN gravitational wave luminosity from
the inspiral phase of a binary system of compact objects moving in a quasi
elliptical orbit is computed using the multipolar post-Minkowskian wave
generation formalism. The necessary inputs for this calculation include the 3PN
accurate mass quadrupole moment for general orbits and the mass octupole and
current quadrupole moments at 2PN. Using the recently obtained 3PN
quasi-Keplerian representation of elliptical orbits the flux is averaged over
the binary's orbit. Supplementing this by the important hereditary
contributions arising from tails, tails-of-tails and tails squared terms
calculated in a previous paper, the complete 3PN energy flux is obtained. The
final result presented in this paper would be needed for the construction of
ready-to-use templates for binaries moving on non-circular orbits, a plausible
class of sources not only for the space based detectors like LISA but also for
the ground based ones.
