  We use simulated Hubble parameter data in the redshift range 0 \leq z \leq 2
to explore the role and power of observational H(z) data in constraining
cosmological parameters of the {\Lambda}CDM model. The error model of the
simulated data is empirically constructed from available measurements and
scales linearly as z increases. By comparing the median figures of merit
calculated from simulated datasets with that of current type Ia supernova data,
we find that as many as 64 further independent measurements of H(z) are needed
to match the parameter constraining power of SNIa. If the error of H(z) could
be lowered to 3%, the same number of future measurements would be needed, but
then the redshift coverage would only be required to reach z = 1. We also show
that accurate measurements of the Hubble constant H_0 can be used as priors to
increase the H(z) data's figure of merit.
