  Non-standard interactions (NSI) between neutrinos and electrons can
significantly modify the decoupling of neutrinos from the plasma. These
interactions have two effects on the overall picture: (i) they alter neutrino
oscillations though matter effects and (ii) they modify the scattering and
annihilation processes involving neutrinos and electrons and positrons. We
study the role of non-universal and flavour-changing NSI in the decoupling and
how they impact the determination of the effective number of neutrinos,
$N_{eff}$. We examine the degeneracies between NSI parameters and we compare
the expected sensitivity from future cosmological surveys with the current
limits from terrestrial experiments. We outline the complementarity between
both approaches.
