We have calculated the electronic coupling, \(J\), between the the excited states of an ergosterol dimer. The ergosterol molecules are separated by distances of 6Å, 7Å and 8Å. To obtain reference values for the coupling, supermolecule calculations were carried out in Gaussian at the CAM-B3LYP/6-31G level of theory. We have tested the numerical requirements of the more approximate method using transition density fitted charges.