Megapack

The Tesla Megapack is a utility-scale battery that plugs into the power grid: one 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?

Each Megapack holds 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.

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 2017 Hornsdale Power Reserve in South Australia, built on Powerpacks, had already shown that a big battery could earn back its cost from frequency control.

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. Each generation has also packed more energy into the same box.

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 metric tons, 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

More energy in each box lowers the cost of storage: more megawatt-hours per shell, per truck, and per hour of labor means a lower cost per kilowatt-hour as volume grows. Tesla builds Megapacks at three Megafactories. Lathrop, California, opened in 2022 and is rated for about 40 gigawatt-hours a year; Shanghai began production in early 2025 with 20 gigawatt-hours a year for export markets; and Brookshire, Texas, near Houston, began building Megapack 3 on August 6, 2026, with a design capacity of 50 gigawatt-hours a year. Tesla also earns money from the software that trades these batteries in power markets, covered in the Autobidder explainer.

Current Status of Megapack

Megapack drives Tesla's storage business, and deployments have grown fast since 2021.

Tesla's total storage deployments grew from 4.0 gigawatt-hours in 2021 to 46.7 in 2025, nearly 12 times as much. Wood Mackenzie placed Tesla and China's Sungrow in the top two spots for battery-storage market share in 2025, the third year in a row, and its separate 2026 scorecard, which weighs factors such as safety and financial strength, ranked Sungrow first and Tesla second. In 2026, deployments were 8.8 gigawatt-hours in the first quarter, 13.5 in the second, and 13.7 in the third. In the second quarter, warranty charges tied to a supplier's cells set the energy business's gross margin, the share of revenue left after the cost of the products, to 20.4 percent. The Lathrop Megafactory passed its 15,000th unit in June 2025, and the Shanghai Megafactory built its 1,000th a month later.

What Comes Next

The near-term path is more volume in more places. Three Megafactories on two continents move Tesla toward the 1 terawatt-hour (1,000 gigawatt-hours) of storage a year it has described as its goal, and the first Megapack 3 customer deliveries from Brookshire are expected by the end of 2026. Those units ship as Megablocks, which Tesla says cut installation time by 23 percent and construction costs by up to 40 percent.

The Bottom Line

Megapack turned grid storage into something Tesla can build, truck, and connect at scale. Megapack 3 and the Brookshire plant carry that scale into the rest of 2026.