Hydrogenated amorphous silicon (a-Si:H) has potential fluctuations, which arise from the heterogeneities, variations in the bond angles, bond lengths, and nonuniform distribution of hydrogen and dopants, etc. We have estimated the potential fluctuations present in undoped and doped a-Si:Ei from the optical as well as from the transport measurements. In the optical measurements, the subgap absorption has been used to estimate the width of the potential fluctuations. In the transport method, the conductivity and the thermopower measured as a function of temperature are used to provide the width of the potential fluctuations, as shown by Overhof and Beyer. We find that in all cases, the width of the potential fluctuations measured by the optical measurements is about 20 times larger than that measured by the transport measurements on the same sample. This is explained by noting that optical absorption is a local process, which is sensitive to the short-range potential fluctuations by the order of 3 Angstrom, whereas the transport measurements are sensitive to the long-range potential fluctuations (approximate to 80 Angstrom) which may have smaller width.