This paper presents a method of path planning for skid-steer robots using an energy-based heuristic. A kinematic model of skid-steer motion utilizing the instantaneous centers of rotation (ICRs) between the tracks and the ground surface is used to predict vehicle motion. A model of skid-steer robot power usage, which also utilizes ICR estimates for slip velocity calculation, is implemented to generate estimates of energy usage. The kinematic and power use models are fused with a Sampling Based Model Predictive Optimization algorithm to plan energy efficient paths through operational areas with mixed surface types. The results of planning paths through both simulated and real-world environments are presented and show that small increases in distance can result in significant energy savings for skid-steer robots.