A 500 MWh Tesla Megapack Battery Just Went Live in Texas

Texas just added a serious chunk of battery muscle to its grid. Ørsted's new Old 300 Storage project in Needville, southwest of Houston, is fully connected to the ERCOT grid and running on Tesla Megapacks. The system is rated at 250 MW/500 MWh, which means that at full output it can push 250 MW onto the grid for two hours straight.

The Megapacks came out of Tesla's Megafactory in Lathrop, California, which Electrek notes is the largest industrial utility-scale battery storage factory in the US. Each Megapack ships as one integrated unit with battery modules, inverters, thermal management, and controls already built in, so far less has to be bolted together on site. In Tesla's current two-hour configuration, a single unit delivers roughly 1.9 MW of power and 3.85 MWh of storage, so a 500 MWh site like this one represents well over a hundred of them lined up in a field.

What the project actually does

Grid batteries are simple in concept: charge when electricity is cheap and plentiful, discharge when the grid is straining. Old 300 Storage can do that, and it can also provide grid services that help manage voltage and frequency. That second job matters a lot in Texas, where demand keeps climbing and extreme weather can tighten the gap between supply and demand in a hurry.

The battery sits next to Ørsted's 430 MW Old 300 Solar farm, but the two operate independently. The storage system is not limited to soaking up solar power from next door; it can charge from and discharge to the wider ERCOT grid as conditions call for it. Old 300 Solar has been running since 2024 and generates enough power annually to serve around 80,000 Texas homes and businesses, according to Ørsted. Together, the solar and battery projects are expected to generate roughly $110 million in property tax revenue for local schools, infrastructure, and emergency services.

"Battery energy storage has played a large role in providing much-needed power to ERCOT in times of tight supply and demand margins," said Melissa Peterson, president of Ørsted Americas Onshore.

For Tesla, it is another 500 MWh notch in a stationary storage business that has quietly become one of the company's strongest performers. Tesla says it now has more than 58 GWh of industrial storage systems operating in over 65 countries. For Ørsted, the project pushes its operating US onshore portfolio to around 6 GW.

Why EV owners should care

This is a utility story, not a product launch, but it touches your garage more than you might think. A few practical takeaways:

• Overnight charging gets more reliable. Batteries that discharge during tight evening peaks help the grid ride through the hours when everyone's AC is running. That is the same grid your Level 2 charger pulls from a few hours later.
• Off-peak charging is still the smart move. Storage helps flatten the daily peak, but you still save money by scheduling charging for late-night or midday solar hours. Set a departure time and a charge window in your car's app rather than plugging in and charging instantly at 6 p.m.
• Your home setup is the weak link, not the grid. A properly installed 240V circuit, a quality Level 2 charger, and the right adapter for public stops do more for your day-to-day charging than any single grid project.
• Texas weather has not gone anywhere. Grid batteries reduce strain; they do not make outages impossible. A portable jump starter, a tire inflator, and a 12V power bank in the frunk are still cheap insurance.

The bigger picture

Every large battery that comes online makes it a little easier for the grid to absorb millions of EVs charging overnight. Two-hour systems like Old 300 are built specifically for the evening ramp, when solar production falls off and household demand spikes. That is the exact window utilities worry about as EV adoption grows, and it is the window that time-of-use rates are designed to steer you away from.

If you charge at home, the best thing you can do is stay flexible: charge on a schedule, keep your daily state of charge in a sensible range, and use hardware that lets you control when the electrons flow. The grid is getting better at handling the load. Your charging habits are the part you actually control.