A pair of Tesla Model S electric vehicles have crossed the US from Los Angeles to New York City in 76 hours. The journey was completed as part of an attempt to break a Guinness World Record for cross-country energy efficiency, but it's not yet clear if the attempt was successful. What is clear is that the teams taking part in the rally completed their journey and were met by Tesla founder Elon Musk at the finish line.

It was predicted that the journey would take "about three days," but poor weather meant the actual journey took three days and four hours. However, the record attempt wasn't about speed; the team was aiming to break the record for "lowest charge time for an electric vehicle traveling across the United States," and the verdict on whether that record was broken will come from Guinness officials monitoring the event.

As with many record attempts, Tesla's is a little arbitrary. The stunt acts as a covert advertisement for the expansion of the company's coast-to-coast Supercharger network, which Musk announced last week is now roughly 80 percent complete. The most recent additions to the network made it possible to drive coast-to-coast using Tesla's rapid-speed chargers for the first time, and this is a pretty effective way to advertise that to would-be buyers. Meanwhile, the Supercharger network continues to expand, and Tesla promises it'll serve 98 percent of the US population by the end of next year.