  We have evaluated excitation energy transfer rates in photosyntetic complexes
using the exact HEOM method and various approximate methods frequently used in
the literature, namely, the F\"orster method, the Redfield method, the modified
Redfield method and the variational master equation. The rates are evaluated
for the case of a simple dimer and a trimer photosynthetic complex, with
vibrational environment characterized by the Drude-Lorentz spectral density.
Comparing approximate rates to the exact ones, we have confirmed the validity
of approximate methods within appropriate limits, however these limits are
often well outside parameter ranges that are relevant for the dynamics in real
photosynthetic complexes.
