  We find that if we live at the center of an inhomogeneity with total density
contrast of roughly 0.1, dark energy is not a cosmological constant at 95%
confidence level. Observational constraints on the equation of state of dark
energy, w, depend strongly on the local matter density around the observer. We
model the local inhomogeneity with an exact spherically symmetric solution
which features a pressureless matter component and a dark-energy fluid with
constant equation of state and negligible sound speed, that reaches a
homogeneous solution at finite radius. We fit this model to observations of the
local expansion rate, distant supernovae and the cosmic microwave background.
We conclude that the possible uncertainty from large-scale structure has to be
taken into account if one wants to progress towards not just precision but also
accurate cosmology.
