The Mercedes-Benz Vision EQXX has completed another efficiency run, this time in the Arabian desert.

The EQXX has managed two previous long trips on a single charge—previously covering 746 miles from Stuttgart, Germany, to the Silverstone racetrack in the U.K. on the second trip. The focus of this third trip, in which the EQXX covered 627.6 miles between the Saudi Arabian capital of Riyadh and Dubai, in the United Arab Emirates, was purely on efficiency, Mercedes explained in a press release.

Averaging 42.7 mph (including time spent stopped, 49.3 mph counting only time spent in motion), with a maximum speed of 87 mph, the EQXX’s average energy consumption was 8.4 miles per kwh. That was in temperatures of up to 93.2 degrees Fahrenheit that put battery thermal management and climate control systems to the test.

Air conditioning was used during the trip but had a minimal negative impact on efficiency, according to Mercedes, thanks to a “multi-source heat pump.” The automaker said a “further developed” version of this heat pump was included in the Concept CLA-Class unveiled at the 2023 Munich auto show as a preview of a family of new EVs with an efficiency focus.

In a drive of the Vision EQXX, Green Car Reports experienced how it manages to escape the weight-and-efficiency spiral that affects EVs. Hopefully, this granular, all-encompassing approach will carry through to these future production model, which will be based on a new platform dubbed Mercedes-Benz Modular Architecture (MMA).

Mercedes-Benz Vision EQXX desert run

Mercedes also used this desert trip to highlight the EQXX’s solar roof, which is comprised of 117 solar cells. It’s used to power ancillary equipment, reducing the energy demand from the battery pack. The roof harvested 1.8 kwh of energy during the trip, adding approximately 15 miles of range, Mercedes claims.

“Research continues into the series-production benefits of this technology,” the release said of the solar roof. So while two solar cars that were nearly at the production stage—the Sono Sion and Lightyear 0—have been cancelled, perhaps Mercedes will find some value and viability for solar power in a luxury car.