Commonly used models for electron energy transport involve free parameters which must be tuned to experiment. Such models often give a poor representation of the effects of self-consistent electric fields. The author briefly discusses the various approaches that have been employed and outlines a novel method which attempts to model the expected effects of such fields. This is as a substitute for accurate solution of the relevant kinetic equations which is totally uneconomic in a two-dimensional simulation code. Simulated X-ray spectra are compared with experimental measurements to assess the performance of the model produced.