  We report on the effect of elastic intervalley scattering on the energy
transport between electrons and phonons in many-valley semiconductors. We
derive a general expression for the electron-phonon energy flow rate at the
limit where elastic intervalley scattering dominates over diffusion. Electron
heating experiments on heavily doped n-type Si samples with electron
concentration in the range $3.5-16.0\times 10^{25}$ m$^{-3}$ are performed at
sub-1 K temperatures. We find a good agreement between the theory and the
experiment.
