One of the basic ways to estimate vehicle speeds at the reconstruction of vehicle collisions is the use of methods generally referred to as “energy methods”, where a relation between the “energy equivalent speed” (EES) and the size of permanent vehicle deformation is described. There are several mathematical models used in practice to describe such a relation. Usually, a linear relation between the deformation size (depth) and the energy consumed to cause the deformation (“deformation work”) is assumed. In contrast, the deformation itself and the deformation energy are described in various ways. In consequence, different EES values may be obtained from the calculations, depending on the model used. In the accident reconstruction practice, an increasingly important role is played by the uncertainty and reliability of the analysis results obtained. This article is dedicated to the uncertainty of estimation of the energy equivalent speed (EES). The uncertainty calculation results obtained with the use of one of the typical methods of determining it, i.e. the total differential method, have been presented. The calculations were carried out for five analytical models used to determine the deformation work, based on the deformation size, for several real cases of post-impact vehicle deformation. The calculation results have been presented in the form of tables and graphs, thanks to which comparisons between both the EES values and the values of their absolute and relative uncertainty could be made. The whole analysis has ended with conclusions concerning the values obtained; they may be a source of information on the uncertainty in determining the EES parameter depending on the computation model used.