Tesla Locks In 1 TWh a Year From a Solar and Battery Behemoth in the Arizona Desert

The most important energy announcement this week did not come from a utility or a government. It came with a groundbreaking ceremony in the Mojave Desert, around 20 miles north of Lake Havasu City, Arizona, where developer ContourGlobal turned the first dirt on Project Sterling: a solar-plus-storage plant that is already mostly spoken for by one of the most demanding corporate electricity buyers on the planet.

Sterling will pair 509 megawatts of DC solar capacity (450 MW of AC output to the grid) with a 360 MW battery system capable of storing 1.4 gigawatt-hours of electricity. That is four hours of full-power discharge from the batteries alone, and ContourGlobal says the combination can deliver clean electricity for up to 16 hours a day. Tesla has signed a long-term power purchase agreement covering around 1 terawatt-hour per year, plus the associated renewable energy certificates: roughly 90 percent of everything the plant is expected to generate. Commercial operation is targeted for 2028.

The deal was signed in July, but this week's groundbreaking marks the moment the paper turned into steel. More than 760,000 solar panels and over 300 battery storage containers will eventually cover more than 2,000 acres. Construction will employ around 400 workers through 2028, and the project has secured an equity bridge loan from a syndicate of international banks to carry it through the construction phase. Once online, Sterling will be ContourGlobal's largest renewable energy asset worldwide.

Tesla's commitment turns Project Sterling from a speculative mega-project into one of the largest corporate solar-plus-storage deals ever signed in the United States.

Why one buyer wants 90 percent of a power plant

Corporate power purchase agreements are hardly new. What makes this one stand out is the scale and the shape of the electrons. One TWh a year is more than many entire utilities serve to their residential customers; pv magazine's reporting put it at roughly the annual residential demand of a city of 100,000 to 120,000 people. And critically, this is not a virtual PPA that trades financial certificates across the grid. It is a physical, deliverable arrangement: Sterling connects to the Western Area Power Administration grid, holds firm point-to-point transmission rights into the California Independent System Operator's market, and is pseudo-tied to CAISO. The power flows to Tesla's Californian operations.

That 16-hour-a-day delivery claim is the detail that matters most. Solar alone cannot do it. A 450 MW solar farm produces at full tilt for a few hours around midday, then fades. The 1.4 GWh battery stack stores the midday surplus and discharges it through the evening, when wholesale prices spike and solar output is zero. This is the grid-scale version of what utilities call a firming asset: it turns an intermittent resource into something that behaves, from the buyer's perspective, close to baseload.

The battery chemistry bet: LFP goes big

Sterling's storage containers use lithium iron phosphate (LFP) batteries with liquid cooling and integrated fire protection. The choice is worth noting. LFP cells trade some energy density for a longer cycle life, better thermal stability, and, historically, lower cost per kilowatt-hour than nickel-based chemistries. For a grid battery that will charge and discharge daily for decades, those trade-offs are exactly right: energy density barely matters when the battery sits in a container in the desert, but cycle life is everything.

The trend across the industry is unmistakable. Utility-scale storage is standardizing on LFP at four-hour durations, which has become the sweet spot for shifting solar output into the evening peak. ContourGlobal's 360 MW / 1.4 GWh sizing fits that template precisely. What is unusual is simply the buyer profile: corporate offtakers of this size have historically favored wind or plain solar. A battery-paired deal of this magnitude signals that big tech-adjacent companies are now willing to pay for dispatchability, not just raw megawatt-hours.

ContourGlobal's biggest PPA ever

For the developer, this is a landmark of a different kind. Antonio Cammisecra, ContourGlobal's president and CEO, has said the Tesla agreement is the company's largest PPA to date, and analysts have described it as one of the largest hybrid solar-plus-storage offtake deals ever signed for a single plant in the United States. ContourGlobal acquired Sterling in the development stage in December 2024, then reshaped the project around Tesla's specific requirements, procuring major equipment through 2025 before breaking ground this week.

The deal also brings ContourGlobal's U.S. portfolio to 2.4 GW of thermal, renewable, and storage capacity operating or under construction. Notably, the company completed a 324 MW solar facility in Colorado just a week before the Sterling groundbreaking, its largest operational solar plant to date. The pipeline is moving fast, and it is moving in the direction of storage-paired assets.

What this says about the power market

Step back and the Sterling deal is a window into where the U.S. electricity market is heading. Corporate demand for clean power is no longer just about annual matching, where a company buys enough renewable certificates to cover its yearly consumption. The emerging standard is around-the-clock clean energy: matching consumption hour by hour, with batteries filling the gaps. Tesla's 16-hour-a-day arrangement at Sterling is another data point on that trend line.

It also underscores the scarcest resource in the AI and electrification boom. Compute capacity gets the headlines, but electricity is the binding constraint, and the companies that can contract firm clean megawatts are securing a structural advantage. Tesla's manufacturing footprint and AI infrastructure consume enormous quantities of power, and a long-term, price-certain supply with bundled renewable certificates is a hedge against both price volatility and grid-constraint risk.

There are caveats, as with any project two years from operation. Permitting, equipment supply chains, and grid interconnection can all slip. The equity bridge financing gets construction started but permanent financing will need to close. And 16 hours of clean delivery still leaves eight hours dependent on the broader grid. But the signal is clear: the era when solar developers built first and found buyers later is fading. The biggest plants are now being engineered, from the ground up, around the needs of a single corporate customer who needs power that behaves like it is always on.