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
0
1133
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 began Megapack 3 production on August 6, 2026. This happened at its newest Megafactory in Brookshire, Texas, near Houston. The plant has a designed capacity of 50 GWh a year, dedicated to this product. Each Megapack 3 holds about 5 MWh and delivers 2.5 MW. Deliveries are not expected until late 2026. So the production line runs ahead of the first customer shipment.

The new unit gains energy without increasing its footprint. Megapack 2 XL held 3.9 MWh. Megapack 3 holds about 5 MWh within the same 28-foot enclosure. This marks a 28% increase in energy density. Tesla switched to larger 2.8-litre cells. It also cut thermal-system connection points by 78%. Fewer joints in a liquid loop mean fewer spots for a field leak to begin.

The Megablock represents a larger change. Tesla bundles up to four Megapack 3 units into a 20 MWh block. This block rates for four-hour discharge. It comes pre-engineered with its transformer and switchgear. Tesla claims up to 248 MWh fits on an acre. The company also claims installation time drops 23%. Construction cost falls 40%. Tesla says a crew is able to deploy 1 GWh in 20 days. These are vendor figures. No third party has published a build to test them.

The factory moved 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. The company met that schedule. Tesla deployed 13.5 GWh of storage in the second quarter. This was up 41% from a year earlier. Energy generation and storage revenue hit $3,139 million, up 13%. This was on roughly $640 million of gross profit.

Why It Matters

Cell supply no longer limits US storage projects. Assembly capacity and interconnection queue position now hold that role. One site rated at 50 GWh a year is nearly four times what Tesla deployed worldwide in the second quarter. Brookshire alone thus shifts the supply picture. It does not just add to it at the margin.

Developers should test the 248 MWh per acre claim. Land and civil work drive a growing share of project costs. A denser block shortens the site a developer needs to permit. Ask a supplier to warrant the density and the 20-day deployment rate in a contract. A specification sheet does not equal a schedule. The first Megablock sites will not energize until 2027.

Critical Perspective

Production start and delivery are different milestones. Tesla ran the first units in August. It expects customer deliveries at the end of 2026. A plant rated at 50 GWh a year does not indicate the rate it holds in month three. Tesla has not published a ramp curve for Brookshire. The 50 GWh figure is a design number.

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

Bigger cells reduce joints and concentrate risk. Moving to 2.8-litre cells removes 78% of thermal-system connection points. This offers a real reliability gain. It also places more stored energy behind each cell wall and thermal path. Buyers should request UL 9540A test data on the new cell. They need this before pricing the safety setback implied by a denser block.