An extensive laboratory test program was used to investigate the performance of silicone rubber material samples of various grades when subjected to inclined-plane test conditions. In this paper, the leakage current and applied voltage waveforms were monitored and stored. The captured waveforms were then analyzed, and a number of parameters characterizing the waveforms (FFT, THD, power, energy, and power factor angle, charge and absorbed energy) were calculated. The use of the calculated parameters as possible indicators of material degradation was investigated. In many cases, no obvious trends with time have emerged. However, the results for the absorbed energy and its rate of change show different trends for samples approaching failure, i.e. end-of-life. These observations may be useful in predicting imminent sample failure, and the derived rate of change of energy absorption factor may be a more quantitative indicator of sample level of degradation and, hence, material classification.