Anticipation continued to build as the 8:00 p.m. Pacific (11 p.m. Eastern) press conference got pushed back to 8:30, and then finally to 9:18, leaving online fans and press watching a live stream of reporters taking pictures of a stage--empty of everything except a backdrop that read "Powerwall Tesla Home Battery." Endless loops of lights and music swirled around the room, powered entirely by battery (though the crowd didn't know that yet).

Finally, Musk took to the stage to announce the launch of "Tesla Energy."

Despite the schedule snafu, Tesla had this moment planned for years. Ground broke on their battery-producing Gigafactory in 2014, and by 2020 the facility will be pumping at full capacity, sending out massive quantities of lithium-ion batteries. They hope to produce more batteries in one year than the entire world produced in 2013.

Some of these will be Powerwalls, huge batteries that can power your home. The Powerwall will come in a 10 kilowatt-hour (kWh) model and a 7 kWh model. The battery comes in a narrow rectangular case that can be mounted inside or outside a residence. Both models will be 220 pounds, 51 inches tall, 33 inches wide, and just 7 inches thick.

Musk wants to boost the amount of renewable energy use in the United States and around the world. "We have this handy fusion reactor in the sky called the sun," he said at the press conference. The idea is to create an easy, efficient way to store energy generated by sunlight during the day that can then be used at night (the 7 kWh version), or store extra energy for emergencies (10 kWh). For comparison, a refrigerator uses about 0.2 kWh and lighting a room uses 0.1 kWh.

So how much will the revolution cost? As of now, the 10 kWh version is going of $3,500 and will start shipping this summer. The Powerwall will only be available in the U.S. initially, but Musk hopes the battery will scale globally, allowing people in developing countries without a robust electrical infrastructure to get electricity quickly without relying on power lines. Up to nine Powerwalls can be stacked together for particularly large houses or small commercial applications.

For larger businesses and utilities who want to go off the grid, there's a bigger version in the works known as the Powerpack, and this is where Musk's vision zooms ahead to a future where energy is generated by renewable resources and stored for future use in giant batteries.

With 2 billion Powerpacks, Musk predicts that the entire world could be powered completely by battery. That's electricity, cars, everything. It might seem impossible, but Musk points out that 2 billion is about the same number of cars that are currently on the road. With a factory that can pump out massive quantities of batteries at a comparatively low price, it's easy to believe Musk when he says that switching over to batteries powered by renewable energy is, "something that we must do, we can do, and we will do."