Megapack

The Tesla Megapack is a utility-scale battery that plugs into the power grid: a single steel box, roughly the footprint of a shipping container, that shows up with its battery modules, an inverter, and a cooling system already wired together at the factory. Utilities and power developers use it to bank extra solar and wind, steady the grid's frequency, and discharge during the evening peak or an outage. Tesla announced it on July 29, 2019, and it is now the workhorse of Tesla Energy, the division Elon launched in 2015 alongside the home Powerwall.

What is the Megapack?

A Megapack is a ready-built battery the size of a shipping container that stores electricity for the power grid. Inside one box sit the battery cells, an inverter, which is the device that turns the battery's direct current into the alternating current the grid uses, and a liquid-cooling system. Because everything is assembled and tested at the factory, a Megapack can be bolted to a concrete pad and connected to the grid in a fraction of the time older systems took. A utility uses it to store cheap midday solar power and release it after sunset, to steady the grid's frequency, and to keep power flowing during outages.

Why the Megapack Exists

The Megapack exists because the battery before it, the smaller Powerpack, was slow to build. Putting up a large site meant bolting together many small cabinets on location, a labor-heavy job that did not scale up to gigawatt-hour grids. Tesla's answer was to build it all into one unit: pack roughly 60% more energy into each box and ship it ready to bolt down, so a 250-megawatt, 1-gigawatt-hour site could rise on a three-acre lot in under three months. The idea was earned in the field. The 2017 Hornsdale Power Reserve in South Australia, built on Powerpacks, proved a big battery could provide frequency control and pay for itself.

Hornsdale was a landmark at 129 megawatt-hours in 2017. The Megapack-era Elkhorn battery at Moss Landing reached 730 megawatt-hours, more than five times the energy, from a product designed to be copied over and over rather than engineered from scratch each time.

How it Works

Each Megapack is a self-contained block. Direct-current battery cells feed an onboard inverter that converts to the grid-standard alternating current, while liquid cooling holds the cells at the right temperature and software manages the charging and discharging. You do not assemble it, you just place it, connect it, and run it. Each unit has also grown denser with every generation.

The energy in each unit climbed from 3 megawatt-hours at launch to 3.9 in 2022 and about 5 in 2025, a gain of roughly two-thirds. Megapack 3 carries that energy in larger 2.8-liter lithium iron phosphate (LFP) cells, runs at 93.7% round-trip efficiency, which is the share of stored energy you get back after charging losses, and weighs about 39 tonnes, shipping on a standard seven-axle trailer with no build needed on site. Four units combine into a "Megablock" of roughly 20 megawatt-hours.

The Economics of the Megapack

The rising energy packed into each box is really a cost-curve story. More megawatt-hours per shell, per truck, and per hour of labor means a falling cost per kilowatt-hour, the kind of efficiency that builds on itself as volume grows. Tesla builds the units at its Lathrop, California Megafactory, which opened in 2022 with room for about 10,000 units a year, and at a second Megafactory that opened in Shanghai in 2025 to serve export markets. Together they can now turn out about 80 gigawatt-hours a year. Beneath the hardware sits a quieter layer of revenue: the software and services that trade these batteries into energy markets on behalf of their owners.

Current Status of Megapack

Megapack now anchors a business that has grown at a startup's pace off an established company's base.

Tesla's total energy-storage deployments grew nearly twelvefold, from about 3.9 gigawatt-hours in 2021 to 46.7 in 2025, which makes Tesla the world's largest energy-storage provider at an estimated 15% of the global grid-scale market. Production keeps pace: the Lathrop Megafactory passed its 15,000th unit in June 2025, and the new Shanghai Megafactory shipped its 1,000th export unit a month later.

What Comes Next

The near-term path is more volume in more places. Two Megafactories on two continents point toward the 1 terawatt-hour (1,000 gigawatt-hours) of deployments a year Tesla has described as its grid-storage goal, with Shanghai opening export markets that Lathrop alone could not reach. Denser cells, the Megablock format, and steady efficiency gains all suggest the per-unit numbers will keep climbing while the cost per kilowatt-hour keeps falling.

The Bottom Line

Megapack took the hardest part of the clean-energy shift, storing power until you need it, and turned it into something you can build, truck, and bolt down at scale. That is why a steel box on a concrete pad has become one of Tesla's fastest-growing businesses and a load-bearing piece of the modern grid. It is the kind of unglamorous, world-changing product Elon builds better than anyone.

Related

Keep reading: Powerpack, Powerwall. Zoom out to the Tesla overview, or open the Tesla Lineup Explorer.