Tesla's massive, 130-acre battery-making Gigafactory isn't due to start production on lithium ion cells until 2017, but a grand opening is due to be held on July 29, a Fortune report states. The date was revealed in email sent to customers, who won invitations to the customer-focused event by referring customers via Tesla's referral program.

Although only 14 percent complete as of early May, according to a Bloomberg report, the factory is already producing Tesla's Powerpacks and Powerwalls. By the time it is fully up and running in 2020, the factory will be producing, Tesla materials state, more lithium ion batteries annually than the rest of the world produced in 2013 combined. This will reduce the cost of production by a projected 30 percent and, in theory at least, in turn reduce the consumer cost of Tesla cars.

The Model 3 Tesla, for example, is being projected to come in at $35,000 compared to the $71,000 Model S, a price point partially enabled by the savings the Gigafactory will bring.

Tesla did not immediately reply to request for comment.