The energy of a Landau-damped electrostatic wave is a long-standing
problem.
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
presented.
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 u_{p} as predicted by fluid theory, but u_{p}/2 in agreement with Landau-damping physics.