The Tesla Megapack is a large-scale rechargeable lithium-ion battery stationary energy storage product, intended for use at battery storage power stations, manufactured by Tesla Energy, the energy subsidiary of Tesla, Inc.

Launched in 2019, a Megapack can store up to 3.9 megawatt-hours (MWh) of electricity. Each Megapack is a container of similar size to an intermodal container. They are designed to be deployed by electric utilities. The energy stored can be used as required, for example during periods of peak electricity demand or when grid power is disrupted.

Tesla Energy also offers the Powerwall, a smaller energy storage device intended for home use.

On April 30, 2015, Tesla announced that it would sell standalone battery storage products to consumers and utilities.^[1] Tesla CEO Elon Musk stated that the company's battery storage products could be used to improve the reliability of intermittent renewable energy sources, such as solar and wind.^[1]

Prior to the Megapack launch, Tesla used its 200 kilowatt-hour (kWh) Powerpack energy storage product to meet the needs of utilities with large-scale storage requirements. During 2015 and 2016, Tesla deployed a combined 300 MWh of Powerwall and Powerpack technology, including an 80 MWh deployment of Powerpacks at the Mira Loma substation in Southern California.^[2] In 2017, Tesla used Powerpacks to deploy 129 MWh of battery storage at the Hornsdale Power Reserve in South Australia,^[3] the biggest deployment of lithium-ion grid battery storage in the world at the time.^[4]

Design work, at Giga Nevada, began on the Megapack project at least as early as the first half of 2018.^[5]

In July 2019, Megapack launched.^[6] It was described by Tesla as a utility-scale energy storage product, suitable for power stations and utilities.^[6] Tesla claimed that Megapacks would be compatible with Tesla power station monitoring and energy control software, Powerhub and Autobidder.^[6] The company stated that Megapack was designed to meet the needs of large-scale battery storage projects, as with the Hornsdale Power Reserve.^[6]

Tesla acquired a former JC Penney's distribution center in Lathrop, California, in 2021 and converted it into a battery plant called Megafactory,^[7] with a target capacity of 40 GWh/year when finished.^[8] Next-generation Megapacks use prismatic lithium iron phosphate cells,^[9] for example in the 585 MWh Kapolei, Hawaii facility.^[10]

Tesla’s record energy deployment was achieved in Q1 2023, adding 3.9 GWh in a single quarter, a 360% year-over-year increase.^{[11][needs update]}

In 2023, Tesla announced a new “Megafactory” in Shanghai to manufacture Megapacks, with the goal of producing about 10,000 packs per year.^[12]

Megapacks are assembled at the Tesla Megafactory in Lathrop, California.

Each Megapack comes with a 15-year "no defect" and "energy retention" warranty.^[15] A 10 or 20 year "performance guarantee" is available for an additional cost.^[15] Once a Megapack has reached the end of its useful life, Tesla says they can be returned for recycling.^[16]

Megapacks are pre-assembled, including "battery modules, bi-directional inverters, a thermal management system, an AC main breaker and controls."^[17]

Tesla requires customers to purchase a maintenance service agreement. Each Megapack receives a minor annual service, and a major service every ten years. The annual maintenance includes inspections and cleaning. The ten-year maintenance includes activities such as replacing the pump and fan for the thermal management system and refilling the coolant fluid.^[18] Maintenance is expected to take about an hour per Megapack.^[16]

The Megapack thermal management system is located at the top of each unit.^[16] It uses coolant fluid, made of an equal-parts mixture of ethylene glycol and water, to keep the battery at operating temperature.^[16]

Each Megapack weighs approximately 51,000 pounds (23,000 kg) and the enclosure is built to a similar size as an intermodal container and includes twistlock fittings to allow automated handling.

Grid batteries are used for ancillary services such as control of frequency and phase, black start, operating reserve etc.

Grid-scale battery standards and fire containment practices are at an early stage of development.^[42]

Fire risks are one factor that has delayed the deployment of some utility energy storage systems. Battery fires cannot be extinguished with water, which is the primary firefighting technique in most communities. A fire in a single cell can cascade to others via thermal runaway, possibly in milliseconds, potentially creating a major hazard. ^[42]

Preventing fires involves multiple layers of protection. First, is to prevent fire in a single cell, by eliminating sparks and short circuits. However, grid-scale systems face potential problems such as coolant leaks and faulty installation. Venting flammable gases and improved insulation reduce cascade risks. Placing controls outside of the container gives more management options. Instead of suppressants, monitoring the situation while watering surrounding areas can help contain the fire. Sensors that track local weather conditions can help avoid overheating. Lithium-free designs with lower fire risks are possible.^[42]

“Plume modeling” attempts to predict how gases from burning battery chemicals might travel. The gases produced vary across battery types, hydrogen fluoride (HF) are of particular concern even at low concentrations. A later plume analysis by Vistra reported that concentrations of HF above California exposure limits could spread across an area 1300 feet in diameter under wind conditions that occur 7 percent of the year.^[42]

In Raquette Lake, New York, the town passed a one-year moratorium preventing battery installation in response to protests citing fires at three New York battery installations. Protestors cited a fire in Lyme New York that burned for four days.^[42]

A Megapack ignited at PG&E's Moss Landing facility in September 2022. The fire led to a day-long shelter-in-place advisory. PG&E stated that safety measures included thermal alarms that can shut down the system, an incident command center, an audible evacuation alarm, pre-fire planning with local fire crews and emergency shut down protocols. Heat-suppression systems, intended to curb thermal runaway, were accidentally triggered, dousing batteries in water that caused arcing and short circuiting. The plant was shut down for months.^[43] Vistra's third installation in Moss Landing adopted the outdoor container model instead of putting the racks under a single roof. (Vistra stated that the outdoor design was chosen to expedite construction.)^[42][44]

In July 2021, one of the 212 Megapack modules at the Victorian Big Battery project caught fire^[45] due to a coolant leak while the battery was unmonitored. That ignited the adjacent Megapack.^[35] Three days later, the fire had burnt itself out as preferred by the fire department.^[46][47][42]

A 50 MW / 100 MWh battery project using Tesla Megapack 2 is under construction in Bouldercombe near Rockhampton, Queensland.^[48] The alternating current section caught fire in September 2023 and spread to the cells of one Megapack module, also damaging the adjacent module. Both modules are being replaced by Tesla. Other 36 modules were operational a couple of days later.^[49]

• Tesla Supercharger Station