The energy of a Landau-damped electrostatic wave is a long-standing
Calculations based on a spatially infinite wave are deficient.
In this paper a wave packet is analysed.
The energy density depends on second-order initial conditions which are
independent of the first-order wave.
Pictures of energy and momentum transfer to resonant electrons are
On physical grounds suitable second-order initial conditions are proposed.
The resulting wave energy agrees with fluid theory.
The ratio between energy and momentum is not the phase velocity up as predicted by fluid theory, but up/2 in agreement with Landau-damping physics.