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A 500 MWh Tesla Megapack battery just went live in Texas
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Tesla Megapacks are now actively supporting the Texas power grid at Ørsted’s newly commissioned Old 300 battery storage project. The 250 MW/500 MWh facility in Needville, southwest of Houston, is fully connected to the Electric Reliability Council of Texas (ERCOT) grid. At full output, the battery energy storage system can deliver 250 MW of power for two consecutive hours, providing critical flexibility to one of the nation’s most strained electricity networks.
The project marks a significant milestone for Ørsted, a Danish renewable energy giant that has been expanding its US onshore footprint. The company already operates the adjacent 430 MW Old 300 Solar farm, which has been generating power since 2024 and serves roughly 80,000 Texas homes and businesses annually. The battery and solar installations operate independently, meaning the Megapacks can charge from and discharge to the wider ERCOT grid, not just the co-located solar array.
All Megapack units were manufactured at Tesla’s Megafactory in Lathrop, California, the largest industrial utility-scale battery storage factory in the United States. Each Megapack arrives fully integrated with battery modules, inverters, thermal management, and controls in a single unit, drastically reducing on-site assembly requirements. Tesla’s current two-hour configuration delivers approximately 1.9 MW of power and 3.85 MWh of energy storage per unit, and dozens of units combine to form the project’s total capacity.
The system provides multiple grid services beyond simple energy shifting. It can charge during periods of plentiful electricity and discharge when demand spikes, while also helping manage voltage and frequency stability. These capabilities are particularly valuable in Texas, where extreme weather events have repeatedly tightened the balance between supply and demand, sometimes leading to emergency conditions.
Local communities are set to benefit significantly from the combined solar and battery development. Ørsted estimates that the two projects will generate around $110 million in property tax revenue for local schools, infrastructure, and emergency services over their lifetime. Moreover, the projects enhance grid resilience for all ERCOT customers, reducing the risk of rolling blackouts during peak summer heat or winter storms.
Industry reactions have been positive, with Ørsted Americas Onshore president Melissa Peterson highlighting the role of battery storage in maintaining grid reliability. “Battery energy storage has played a large role in providing much-needed power to ERCOT in times of tight supply and demand margins,” Peterson stated. The sentiment aligns with broader analyst views that storage is rapidly becoming indispensable as renewable energy penetration grows.
Looking ahead, this 500 MWh deployment strengthens Tesla’s stationary storage business, which now exceeds 58 GWh of industrial systems operating across more than 65 countries. It also expands Ørsted’s operating US onshore portfolio to roughly 6 GW. With Texas leading the nation in battery storage additions, more projects of this scale are expected to come online in the coming years.
The Old 300 project exemplifies a larger national trend of pairing renewables with large-scale storage to create dispatchable clean energy. As coal and gas plants retire, storage systems like Megapacks are stepping in to provide the flexibility that grids need. With falling battery costs and rising demand for reliable power, such hybrid projects are likely to become a standard feature of America’s energy landscape.
