The electron-transfer rate as a function of the free energy gap (energy-gap law) was formulated by including the solvent nonlinear response effect and averaging over the distribution of donor-acceptor distances. Using the same parameter values, we fit the theoretical energy-gap laws to three independent experimental measurements: the photoinduced charge-separation (CS) rate as measured from fluorescence quenching in the stationary state, the actual photoinduced charge-separation rate as obtained from analysis of the transient effect in the fluorescence decay curve, and the charge-recombination (CR) rate of the geminate radical-ion pair. The different energy-gap laws among those reactions can be reproduced reasonably well by adopting different distributions of the donor-acceptor distance: that of the CS reaction covering those over various distances and more specified ones corresponding to the contact ion-pair (CIP) and solvent-separated ion-pair (SSIP) models for the CR reaction. The nonlinear effect in those homogeneous reactions is small when the CIP model applies and appreciable when the SSIP model applies.