Path efficiency is the length of the path actually traversed versus the length of the optimal path. If a robot has complete knowledge of the terrain between it and its goal and unlimited time, then it is possible to plan an optimal path to that goal. Complete knowledge is not available because robot sensors have limited range. Knowledge is also limited by features in the terrain that are shadowed by other portions of terrain. This research uses data from both simulations and actual field trials to determine the effects of sensor range on rover path efficiency. Results from both simulation and field trials with the SR2 rover indicate that in terrain typical for planetary rovers (i.e., terrain without foliage and with broken features) sensor range has a surprisingly low impact on path efficiency.