  We compare perturbations in a fluid model of dark energy with those in a
scalar field. As compared to the $\Lambda$CDM model, large scale matter power
spectrum is suppressed in fluid model as well as in a generic quintessence dark
energy model.To check the efficacy of fluid description of dark energy in
emulating a scalar field, we consider a potential which gives the same
background evolution as a fluid with a constant equation of state. We show that
for sub-Hubble scales, a fluid model effectively emulates a scalar field model.
At larger scales, where dark energy perturbations may play a significant role,
the fluid analogy breaks down and the evolution of matter density contrast
depends on individual scalar field models.
