From arbitrage to asset: How batteries became ERCOT’s summer backbone

Over the past two years, ERCOT’s summer peaks and record renewable output have become the proving ground for a new grid stabilizer: large-scale batteries. In an ESS News exclusive conversation with Mona Tierney-Lloyd, Head of Regulatory & Institutional Affairs at Enel North America, the discussion traced how 1.4 GW of battery energy storage has quietly shifted from pilot projects to an essential reliability backstop and what that means for the future of U.S. power markets.

When solar and wind flood the Texas grid, prices plummet; when demand spikes at dusk, they skyrocket. Enel’s playbook is as simple as playing into this market.

As Tierney-Lloyd explains, “We charge our batteries when solar and wind flood the grid, then deploy that capacity at summer net-peaks, capturing arbitrage value while shoring up reliability when ERCOT needs it most.” That dual mandate of economic upside plus emergency support turned vulnerabilities associated with renewable overproduction into a strategic asset.

During last summer’s heat waves, thermal generators strained under prolonged demand. Storage assets like Enel’s responded in real time.

“Between 2023 and 2024, the growth in battery storage was so significant it literally helped avert emergency grid conditions during the summer heat,” she said. ERCOT’s price signals met responsive megawatts, reducing the risk of rolling outages.

Despite ERCOT’s reputation for speed, interconnection remains a bottleneck. “You’re still looking at a two-to-four-year horizon to get a standalone storage project from queue to commissioning,” Tierney-Lloyd noted. That lag has nudged developers toward hybrid configurations, pairing storage with solar or wind to streamline permitting, financing, and interconnection in a single package.

Technology choices remain pragmatic. While long-duration storage attracts attention, Enel has stuck to lithium-ion. “We’ve deployed only lithium-ion to date. Long-duration technologies face too wide a price gap and uncertain market signals to pencil out right now,” Tierney-Lloyd said.

Safety is another growing focus, especially as batteries move closer to urban load centers. “It’s not an afterthought. Our BESS designs include integrated fire suppression, and we run drills with local fire departments to ensure a coordinated response,” she said. That kind of operational engagement builds trust, which Tierney-Lloyd sees as essential to siting and community acceptance.

Outside Texas, the same themes persist: demand growth, long queues, and aging transmission. ERCOT may be quicker to commission, but other markets will need to accelerate if they hope to avoid similar reliability crunches. Enel’s U.S. experience suggests that bundling technologies and locations can reduce friction and hedge against curtailment and congestion.

Tierney-Lloyd puts a bow on it, “These assets are capturing arbitrage value while shoring up reliability,” a concise summary of how batteries have become a bridge between today’s renewable volatility and tomorrow’s grid resilience.