Ørsted’s Old 300 Storage Reaches Commercial Operation With 500 MWh on Texas Grid
Ørsted's 250 MW/500 MWh Old 300 Storage battery project has entered commercial operation in Fort Bend County, adding a two-hour battery resource to ERCOT alongside the existing 430 MW Old 300 Solar Center.
Published · Updated · 4 min read
The Old 300 Storage Texas battery has reached commercial operation in Needville, Fort Bend County, adding a 250 MW/500 MWh battery energy storage system to the ERCOT grid, Ørsted confirmed this week. The milestone matters because the two-hour battery adds dispatchable capacity in one of the fastest-growing electricity markets in the United States while operating alongside a 430 MW solar facility already producing power at the site.
Old 300 Storage uses Tesla Megapacks manufactured in Lathrop, California, and is fully integrated with ERCOT, according to Ørsted. The battery is co-located with the Old 300 Solar Center but operates independently from the solar project, allowing it to participate as a separate storage resource rather than functioning solely as a solar-charging system.
The project adds 500 MWh of storage to ERCOT
Reporting published August 6 on the commercial-operation milestone confirms Old 300 Storage has entered service at its full 250 MW/500 MWh configuration.
That capacity gives the facility approximately two hours of energy storage at its maximum rated output. The battery can absorb electricity when conditions favor charging and return power to the grid during periods when supply is tighter or market demand is higher.
When Ørsted announced construction of Old 300 Storage in April 2025, the company said battery storage was playing an increasingly important role in ERCOT during periods of tight supply and demand margins.
The project has now moved from that construction phase into commercial operation.
Old 300 sits alongside 430 MW of operating solar
The battery shares a site with Ørsted’s 430 MW Old 300 Solar Center, which completed its final construction phase in 2024.
Ørsted lists Old 300 Solar among its operating U.S. solar projects in Fort Bend County. The solar facility supplies enough annual electricity for tens of thousands of homes and businesses, according to the developer.
Co-locating solar and storage can offer infrastructure and land-use efficiencies, but the configuration at Old 300 is important to understand correctly: Ørsted says the battery was built and is operated independently from the existing solar facility.
The Old 300 Storage Texas battery can therefore respond to broader ERCOT system and market conditions rather than being described simply as storage attached to the output of the neighboring solar farm.
Tesla Megapacks provide the storage hardware
The facility uses utility-scale Tesla Megapack battery systems manufactured at Tesla’s Lathrop, California, plant.
Ørsted said during construction that it worked with the Fort Bend County Fire Marshal on emergency-response planning and would provide on-site battery-safety training with local first responders.
That work is increasingly significant as Texas adds large battery installations and communities develop emergency procedures specifically for lithium-ion energy storage facilities.
Battery projects require fire detection, thermal management, electrical protection, emergency isolation and response planning that differ from conventional generation facilities.
The battery enters a rapidly changing ERCOT market
Texas has become one of the most important battery-storage markets in the United States as solar generation and electricity demand both expand.
Batteries can charge during lower-priced periods and discharge during periods of higher demand, while also providing services that help grid operators balance electricity supply and consumption.
Ørsted’s original project announcement cited ERCOT projections showing substantial electricity-demand growth and described storage as one component of a broader mix needed to maintain reliability.
The need for flexible resources is becoming more prominent as Texas simultaneously adds renewable generation, industrial loads, population and large data centers.
Old 300 expands Ørsted’s U.S. battery portfolio
Old 300 is not Ørsted’s first large battery project in the United States.
The company’s portfolio also includes the Eleven Mile Solar Center in Arizona, which combines 300 MW of solar generation with a 300 MW/1,200 MWh battery system. That project entered commercial operation in 2024.
Ørsted’s solar and storage portfolio also includes other operating solar assets in Texas and the Southwest.
With Old 300 Storage now operating, the company has added another large grid-scale battery in a market where storage is increasingly being used as a mainstream capacity and flexibility resource.
The solar and battery projects represent a larger local investment
Ørsted previously estimated that the battery alone would contribute more than $40 million to the Fort Bend County tax base over its operating life.
Following commercial operation, the developer estimates the combined Old 300 solar and storage projects will generate approximately $110 million in property-tax revenue for the local area.
Those estimates are company projections and will depend on the projects’ actual operating lives, tax treatment and other economic factors.
The operational milestone is more concrete: 250 MW of battery power and 500 MWh of energy capacity are now available as part of the ERCOT system.
As Texas power demand continues to rise, Old 300 illustrates how large solar projects are increasingly sharing sites and grid infrastructure with independently operated batteries that can respond when electricity is needed rather than only when renewable generation is available.
