If you drive an electric vehicle around Offenbach today, you notice something on vacation trips that combustion drivers never had to think about: every extra item on the roof costs noticeable range. This article explains why rear boxes are almost always the better choice for EVs, and what you need to know.

The problem: aerodynamics meet battery capacity

A roof box increases your vehicle's drag coefficient. With a combustion car, you notice this as 1–2 liters of extra fuel per 100 km – annoying but manageable.

With an EV, the same aerodynamic penalty plays out differently: percentage-wise consumption increases similarly, but absolute range drops more noticeably. At 100 km/h autobahn speed, EV drivers report range losses of 15–30 %, depending on the model, roof box size, and weather.

Concretely: an EV with 400 km WLTP range can drop to 280–300 km real-world range with a large roof box on autobahn trips. On a journey south, that's quickly one or two extra charging stops.

The solution: a rear box

Rear boxes mount on the tow bar and sit in the vehicle's slipstream. The impact on drag is significantly lower than with a roof box – measurements suggest 3–7 % range loss, depending on vehicle and rear box model.

For an average trip south, that typically means 1 extra charging stop per day, not 2 or 3.

Other rear box benefits for EV drivers

Easy loading: no hoisting luggage overhead, especially useful when the roof is a panoramic glass panel
No change to vehicle height: parking garages, underground garages, and private garages stay accessible
Quick on and off: some rear box systems install in under 10 minutes

What you need

A tow bar. Without one, it's not an option. Most EVs can be ordered with or retrofitted to have a tow bar (retrofitting typically runs €600–1,500 – worth it if you travel often).
Sufficient nose weight capacity. The tow bar has to handle the rear box plus contents. Most EV SUVs handle 75–100 kg – enough for a fully loaded rear box.
Duplicate license plate. The rear box covers the original plate. We include the duplicate plate as an add-on to the rental.

Which rear box for which trip?

2 people, 1 week: a 300-liter rear box usually works
Family, 2 weeks: 400–450-liter rear box, for example Thule Arcos L or XL
Winter ski trip: 450-liter rear box with interior length for skis up to 175 cm

A common argument against rear boxes is smaller volume compared to roof boxes (max 450 L vs. 600 L). True, but for most family vacations it's not the deciding factor.

Practical tip

If you're unsure: send us your vehicle model and a rough estimate of luggage volume – we'll calculate which rear box fits and what range loss to expect. Our pickup location in Darmstadt is 25–30 minutes from Offenbach via the A5.