The gravitational lensing distortion of distant sources by the large-scale distribution of matter in the Universe has been extensively studied .
In contrast , very little is known about the effects due to the large-scale distribution of dark energy .
We discuss the use of Type Ia supernovae as probes of the spatial inhomogeneity and anisotropy of dark energy .
We show that a shallow , almost all-sky survey can limit rms dark energy fluctuations at the horizon scale down to a fractional energy density of \sim 10 ^ { -4 } .