An enormous Tesla-installed power storage facility is up and running at Southern California Edison’s Mira Loma substation in Ontario, California. The facility, announced last fall, holds enough energy to power 15,000 homes for four hours — 80 megawatt hours of electricity with a peak output of 20 megawatts.

It’s designed to reduce the need for “peaker plants” — electricity generation facilities that run when electricity demands are particularly high, such as on a hot afternoon when air conditioners are running full tilt. They’re expensive to install and maintain, especially when in some areas they might only be used for a few hours a day — or even a year.

The 396 Powerpacks that Tesla installed (it acted as its own general contractor) for SCE were all assembled at the company’s Gigafactory in Nevada. Though 80 megawatt hours of batteries might seem like a lot, it’s the same amount of battery capacity that the company puts into its cars in just three or four days of production.

The SCE facility at Mira Loma has 396 Powerpacks, each with 16 pods of batteries inside. Each pod has 12 bricks of cells, and each brick has 85 battery cells. Add ‘em all up and it’s 6,462,720 individual “2170” battery cells, so named because they’re 21 x 70mm cylinders.

The new cell for the Model 3 will also be made at the #Gigafactory pic.twitter.com/DHldjJCqcS — Jude Burger (@JudeBurger) July 30, 2016

In addition to utility-grade storage systems like this, Tesla’s Powerpacks can also be used with solar panels or other small-scale electricity generation to build microgrids, small electrical systems for entire islands or other remote facilities.

Stationary energy storage has the potential to be big business for Tesla. Whether for big utilities like this project, as an alternative to diesel-generator backup systems at commercial or industrial buildings, or by using Tesla’s smaller Powerwall system at residences (a Powerpack is made up of 16 Powerwalls worth of batteries), expect the number of big battery installations to grow. Tesla CEO Elon Musk predicted last year that the battery business would "have a growth rate probably several times that of what the car business is per year.”

While the majority of the battery production at the Gigafactory, which began last month, will eventually make its way into Tesla’s cars, the massive cell production will also drive down costs for stationary battery storage as well, making these sorts of enormous battery projects much more cost effective.

Stationary batteries and the solar panel business that Tesla acquired in the SolarCity acquisition, are just two of the reasons why Tesla Motors changed its name to Tesla last week. It’s not just about the cars anymore.