I have never carried a kayak for a long enough distance to figure out the range impact, but it will be at least 30% I would think. I use the Thule rack system, which is rugged, smart looking and easy to assemble and disassemble. The only disadvantage of my rack is the slight whistling noise I hear when its raining. I keep the rack on the top all the time, and I have not noticed a range impact from it. The range of my three year old Bolt has dropped a slight amount over time anyway, which is typical of electric cars. In winter, of course, the range is impacted significantly due to heater use, and possibly battery temperature issues. Winter has the most impact on range that I have seen.