According to the Wall Street Journal, U.S. car sales in 2015 jumped to a record high, clearing a peak last reached 15 years ago as cheap gasoline, employment gains and low interest rates spurred Americans to snap up new vehicles. You might think low gas prices would adversely affect Tesla, but it didn’t. 2015 was a great year for America’s favorite electric carmaker with shipments exceeding expectations, according to Fortune.com. The trouble isn’t selling Teslas, it’s making them. The carmaker is struggling get their new Model X and SUV into production, while making sure to meet the demand for the Model S. Too much interest, that’s a nice problem to have—right?