Tesla Starts Megapack 3 Production in Texas at 5 MWh a Unit, With Deliveries Held to Late 2026

Energy Storage Product Utility-Scale BESS
Marin Holt
September 4, 2026
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6 minutes read

Megapack 3 unit: 5 MWh, 2.5 MW
Factory capacity: 50 GWh a year at Brookshire, Texas
Energy density gain: 28% over the 3.9 MWh Megapack 2 XL
Megablock: 20 MWh, up to 248 MWh an acre
Tesla Q2 2026 storage: 13.5 GWh deployed, up 41%

Tesla started Megapack 3 production on August 6, 2026 at its newest Megafactory in Brookshire, Texas, outside Houston. The plant carries a designed capacity of 50 GWh a year dedicated to the product. Each Megapack 3 holds about 5 MWh and puts out 2.5 MW. Deliveries are not expected until the end of 2026, so the line runs ahead of the first customer shipment.

The unit gains energy without gaining ground. Megapack 2 XL held 3.9 MWh. Megapack 3 holds about 5 MWh in the same 28-foot enclosure, a 28% increase in energy density. Tesla moved to larger 2.8-litre cells and cut thermal-system connection points by 78%. Fewer joints in a liquid loop means fewer places for a field leak to start.

The bigger change is the Megablock. Tesla bundles up to four Megapack 3 units into a 20 MWh block rated for four-hour discharge, pre-engineered with its transformer and switchgear. Tesla claims up to 248 MWh fits on an acre. It also claims installation time falls 23%, construction cost falls 40%, and a crew is able to deploy 1 GWh in 20 days. Those are vendor figures, and no third party has published a build to test them.

The factory went from groundbreaking to operation in 16 months. Tesla told investors in its second-quarter filing that Megapack 3 and Megablock production would start this year at the Texas plant. It hit that schedule. The company deployed 13.5 GWh of storage in the second quarter, up 41% from a year earlier. Energy generation and storage revenue reached $3,139 million, up 13%, on roughly $640 million of gross profit.

Why It Matters

Cell supply stopped being the binding limit on US storage projects. Assembly capacity and interconnection queue position took its place. One site rated at 50 GWh a year is close to four times what Tesla deployed worldwide in the second quarter. Brookshire alone therefore shifts the supply picture rather than adding to it at the margin.

For developers, the number to test is 248 MWh per acre. Land and civil work drive a growing share of project cost, and a denser block shortens the site a developer has to permit. Ask a supplier to warrant the density and the 20-day deployment rate in a contract. A specification sheet is not a schedule, and the first Megablock sites will not energise until 2027.

Critical Perspective

Production start and delivery are not the same milestone. Tesla ran the first units in August and expects customer deliveries at the end of 2026. A plant rated at 50 GWh a year says nothing about the rate it holds in month three. Tesla has not published a ramp curve for Brookshire, and the 50 GWh figure is a design number.

The Megablock claims come from the vendor alone. The 23% installation saving, the 40% construction saving, the 248 MWh an acre and the 1 GWh in 20 days all originate with Tesla. No independent site has reported against them, because no Megablock site exists yet. Density figures also assume a site layout that fire code, spacing rules and local permitting will test.

Bigger cells cut joints and concentrate risk. Moving to 2.8-litre cells removes 78% of thermal-system connection points, which is a real reliability gain. It also puts more stored energy behind each cell wall and each thermal path. Buyers should ask for the UL 9540A test data on the new cell before they price the safety setback that a denser block implies.