Tesla Unveils Modular 20MWh Large-Scale Energy Storage System

2025-09-12 | Calvin

On the evening of September 8th, Tesla officially launched its grid-scale energy storage system, Megapack 3, along with the integrated system solution Megablock, which combines Megapack 3 with transformers and switchgear.

The Megapack 3 has increased its single-unit capacity from 3.9 MWh in the previous generation to 5 MWh. Measuring 28 feet in length and weighing 86,000 pounds, it features a simplified cooling system, 78% fewer connection points, and a lower failure rate, capable of stable operation in temperatures ranging from -40°C to 60°C.

The Megablock is composed of four Megapack 3 units combined with high-voltage transformers and switchgear, achieving a total energy capacity of 20 MWh. Its energy efficiency on the medium-voltage side reaches 91%, with a service life of 25 years and over 10,000 charge-discharge cycles. The energy density per acre is 248 MWh.

Since the Megablock is pre-installed in the factory, installation speed is increased by 23%. It can be transported by ordinary trucks without additional permits. A 1 GWh project can be deployed in just 20 working days, reducing construction costs by 40%.

In terms of production capacity, Tesla plans to manufacture Megapack 3 at its new Gigafactory in Houston, with deliveries expected to begin in the second half of 2026, reaching a capacity of 50 GWh.

Currently, Tesla’s California and Shanghai factories produce approximately 80 GWh per year. With the addition of the Houston factory, Tesla’s total energy storage capacity is expected to reach 130 GWh per year by the second half of 2026.

Notably, due to surging demand from renewable energy, data centers, electric vehicles, and grid upgrades, the U.S. is experiencing a severe shortage of medium- and high-voltage transformers. In particular, 30% of high-voltage transformers are in short supply, with delivery times of up to 3 years. Medium-voltage transformers face a 10% shortage and an average delivery time of 1 year. This is expected to delay energy storage projects and increase costs by 10%-20%.

To address the transformer shortage, Tesla will begin producing transformers starting in the second half of 2026.