Finite element analysis was used to simulate water tree degradation in EPR-insulated medium voltage cables under changing environmental conditions. A water tree with an elliptical geometry was allowed to grow inwards from the outer edge of the insulation up to the conductor. Electric field strength and electrical conductivity values were obtained at various locations along the growth path and used to calculate the corresponding specific energy absorption rates (SARs). SAR is a measure of the energy absorbed per unit mass of dielectric material and is used in this study as a measure of insulation degradation. It was found that for each environmental condition, the SAR continually increases along the growth path and exceeds the breakdown SAR of the material just prior to entering the conductor shield. Upon entering this region, there is a drastic decrease in SAR which continues until reaching the conductor where the electric field and thus any SAR become nonexistent. In addition, SAR is directly correlated with a localized rise in temperature of the insulation further synergistically increasing the rate of polymer degradation at the water tree pole.