  In this paper, we explore propagation of energy flux in the future Poincar\'e
patch of de Sitter spacetime. We present two results. First, we compute the
flux integral of energy using the symplectic current density of the covariant
phase space approach on hypersurfaces of constant radial physical distance.
Using this computation we show that in the tt-projection, the integrand in the
energy flux expression on the cosmological horizon is same as that on the
future null infinity. This suggests that propagation of energy flux in de
Sitter spacetime is sharp. Second, we relate our energy flux expression in
tt-projection to a previously obtained expression using the Isaacson
stress-tensor approach. We also comment on the energy flux computation in
TT-gauge on hypersurfaces of constant radial physical distance.
