  We study the quantum backreaction from inflationary fluctuations of a very
light, non-minimally coupled spectator scalar and show that it is a viable
candiate for dark energy. The problem is solved by suitably adapting the
formalism of stochastic inflation. This allows us to self-consistently account
for the backreaction on the background expansion rate of the Universe where its
effects are large. This framework is equivalent to that of semiclassical
gravity in which matter vacuum fluctuations are included at the one loop level,
but purely quantum gravitational fluctuations are neglected. Our results show
that dark energy in our model can be characterized by a distinct effective
equation of state parameter (as a function of redshift) which allows for
testing of the model at the level of the background.
