A towbar box is generally more fuel-efficient than a roof box. Because a towbar box hangs behind the car instead of on top, it disrupts the airflow much less. A roof box significantly increases air resistance, which directly leads to higher fuel consumption. The difference can amount to several percent extra consumption per kilometer, depending on driving speed and the box. In this article, we answer the most frequently asked questions about the fuel consumption of both options.

How much extra fuel does a roof box cost?

A roof box increases fuel consumption by an average of five to fifteen percent, depending on driving speed, the size of the box, and the dynamic characteristics of the model. At higher speeds, such as on the motorway, the effect is greatest because air resistance increases exponentially as you drive faster.

The reason is simple: a roof box places a large volume on top of the car, precisely where airflow is most sensitive. The car has to work harder to overcome that extra resistance, and that costs fuel. A well-designed roof box minimizes this effect as much as possible through a streamlined shape, but it cannot be completely neutralized.

If you mainly drive in the city or over shorter distances, you will hardly notice the difference. But on a long holiday trip to the South of France or Italy, where you drive hundreds of kilometers on the highway, the extra consumption definitely adds up. If you drive an electric car, the extra air resistance also has a direct impact on the driving range.

If you want to keep the extra consumption as low as possible, choose a roof box with a low profile and a sleek aerodynamic design. At VDL Hapro Our aero roof boxes have been dynamically tested so that they cause as little extra drag as possible.

How does a towbar box affect fuel consumption?

A tow bar case It affects fuel consumption less than a roof box, but still has a measurable effect. The box hangs behind the car and hardly increases the frontal area, so air resistance remains limited. However, the extra weight the engine has to pull does result in slightly increased consumption, particularly when accelerating and driving uphill.

A towbar box does disrupt the airflow behind the car somewhat. Modern passenger cars are designed so that air flows smoothly along the bodywork and converges neatly at the rear. A box hanging behind the towbar interrupts that flow, but the effect is significantly smaller than with a roof box.

In addition, weight plays a role. A fully loaded roof box adds weight that the motorcycle has to overcome with every acceleration and when driving uphill. However, this is a limited effect compared to the increase in air resistance caused by a roof box at higher speeds.

What is the difference in fuel consumption between a towbar box and a roof box?

The concrete difference in fuel consumption between a towbar box and a roof box averages between three and ten percent extra consumption for the roof box compared to the towbar box. This difference is most pronounced at speeds above one hundred kilometers per hour, where air resistance becomes the dominant factor.

By way of illustration: if your car normally gets 12 miles per gallon, a roof box can reduce that to 10 or 11 miles per gallon on the highway. A towbar box has a much more modest effect and, in many cases, can be compared to carrying an extra passenger in terms of the weight effect.

Under which driving conditions is the difference greatest?

The difference in fuel consumption is greatest at higher speeds on the highway. Air resistance increases quadratically with speed, which means that the effect is much greater at 120 kilometers per hour than at 60 kilometers per hour. Therefore, a roof box on the highway costs considerably more than the same box in city traffic.

Does the size of the suitcase matter?

Yes, size makes a clear difference. A larger roof box has a larger frontal area and a higher profile height, which creates more air resistance. A more compact roof box with a low profile has less impact on fuel consumption. With a towbar box, size is less of a determining factor for fuel consumption, because the frontal area of the car hardly changes.

What other factors determine the choice between a roof box and a towbar box?

In addition to fuel consumption, ease of loading, available space, the type of car, and the practical situation at home play a major role in the choice between a roof box and a towbar box. For most families going on holiday, overall usability is at least as important as the difference in consumption.

Ease of charging and accessibility

A towbar box hangs at a comfortable height behind the car, making loading and unloading easy. You don't have to lift anything up. A roof box requires you to lift bags and suitcases to roof level, which can be difficult with a taller car or when carrying children. If you have back problems or drive an SUV, a towbar box is more practical for everyday use.

Access to the trunk and parking

A towbar box blocks the car's tailgate, which means you cannot easily access the trunk when the box is full. This is an important point to consider if you frequently need items while on the road. A roof box leaves the trunk completely free. Additionally, a towbar box can present extra challenges when parking tightly in a parking space due to the extra length behind the car.

Is there a tow bar?

A towbar roof box naturally requires a towbar. Not every car comes with one as standard, and having a towbar fitted involves costs. If you already have a towbar, switching to a towbar roof box is simple. If you don't, a roof box is often the faster and cheaper solution to create extra luggage space.

Are you unsure which solution best suits your situation? Feel free to contact us. contact us and we help you make the right choice for your car and travel needs.