After months of endless construction, Tesla’s gargantuan Gigafactory in Sparks, Nevada welcomed guests and select members of the press for a celebratory grand opening event last week.

The Gigafactory is planned to produce 35GWh of cells and 50GWh of packs per year by 2020. Tesla projects that the Gigafactory will employ about 6,500 people by 2020. Panasonic ...