  We show that the dipole of the luminosity distance is a useful observational
tool which allows us to determine the Hubble parameter as a function of the
redshift H(z). We determine the number of supernovae needed to achieve a given
precision for H(z) and to distinguish between different models for dark energy.
We analyse a sample of nearby supernovae and find a dipole consistent with the
cosmic microwave background at a significance of more than 2 sigma.
