The Garage Accessories

Roof Racks are Wasting Your Gas

Americans buy an extra 100 million gallons of gas every year because of them.

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Roof racks reduce gas mileage. Everyone knows that. However, we never knew exactly how much extra gas Americans slurp up annually because of roof racks. According to two researchers at Lawrence Berkeley National Laboratory and the National Renewable Energy Laboratory, now we do: 100 million gallons in 2015. Their study, said to be the first of its kind, which considered the entire US light vehicle fleet and various roof rack configurations instead of individual vehicles, revealed the finding in a paper called “Fuel Consumption Impacts of Auto Roof Racks” in the journal Energy Policy.

From one vantage point, 100 million gallons is a tiny number, just 0.8 percent of total US light-duty fuel use. On the other hand, checking out the energy, emissions, and conservation equivalents of 100 million gallons on the EPA’s Greenhouse Gas Equivalencies Calculator, the figures are impressive: it equals about 282,127 tons of waste being recycled instead of sent to a landfill, or burning 948,452,508 pounds of coal, or the greenhouse gas emissions from a single car driving 2,131,175,060 miles, or the electricity use of 129,699 homes for an entire year. All of this just from keeping that little erector set on top of your car.

Study authors Alan Meier and Yuche Chen predict the numbers are headed up, spectacularly so. Anticipating roof-rack usage to explode by 200 percent through 2040, we will consume six times more fuel due to roof racks than the amount of fuel we expect to save due to hydrogen fuel cell vehicles. The consumption will eat up almost half the expected fuel savings we get from battery electric vehicles. Tesla would need to sell 1.7 Model 3s to make up for a single Subaru with a roof rack.

The study figures we could save 1.2 billion gallons of gasoline over the next 26 years with new design and legislative approaches to reducing the aerodynamic impact of roof racks. Those 1.2 billion gallons are the equivalent of replacing the city of Philadelphia with a forest. The legal approach isn’t going to happen – even the looniest body politic won’t mandate removing roof racks that aren’t in use, or stay in office long enough to see it through. But if a rack maker ever decides to design an aerodynamic rack that doesn’t need 38 minutes and the fine motor skills of an Operation champion to remove, that would be a good start.