Tesla has locked in one of the largest corporate solar-plus-storage power purchase agreements in U.S. history, securing roughly 1 terawatt-hour of electricity annually from ContourGlobal’s Project Sterling in Arizona. The multi-year deal, set to begin when the 509 MWp solar and 360 MW/1.4 GWh battery facility comes online in early 2028, gives Tesla a massive, predictable stream of renewable power—and a blueprint for how tech companies can harness storage to make solar work around the clock.
Breaking Down the Numbers
Project Sterling is not your typical solar farm. ContourGlobal plans to build 509 peak megawatts of photovoltaic panels—yielding 450 MWac—alongside a battery system capable of discharging 360 MW for four hours, totaling 1.4 GWh of stored energy. That alone sets it apart: most solar plants lack storage, forcing grid operators to manage the daily imbalance between midday generation and evening demand.
Tesla’s contract covers about 90% of the plant’s annual output, which ContourGlobal expects to exceed 1.1 TWh. That means Tesla will offtake roughly 1 TWh per year—equal to 1 billion kilowatt-hours. To put that in context, the average American home uses about 10,500 kWh per year, so Tesla’s purchase could theoretically power nearly 100,000 homes. But Tesla is not a utility. The electricity will likely supply the company’s own operations: Gigafactories in Nevada, Texas, and Berlin; Supercharger stations; and perhaps its growing fleet of data centers for AI training and Autopilot.
As first reported by Power Technology and independently covered by Solar Power World, the PPA also includes renewable energy certificates (RECs), allowing Tesla to count the clean power toward its sustainability targets. ContourGlobal acquired the project in December 2024 and reshaped the design to meet Tesla’s requirements—a sign of how large buyers now steer project development.
Why a Battery Changes Everything
The battery is not just backup. It’s an arbitrage tool. By charging during midday when solar output peaks, then discharging in the late afternoon and evening when demand and prices spike, the battery turns a solar-only project into a firm, dispatchable resource. For Tesla, this means the electricity it buys is not tied to the sun’s schedule. ContourGlobal explicitly notes that the battery can shift generation into higher-demand periods, making the PPA more valuable than a simple solar contract.
Location matters, too. Sterling interconnects to the Western Area Power Administration (WAPA) grid and holds firm transmission rights into California’s CAISO market. That transmission link allows the project to export power to California, where evening demand is met largely by natural gas plants and wholesale prices are often higher. Tesla’s offtake can thus serve its California operations—like the Fremont factory and corporate headquarters—with cleaner, possibly cheaper electricity, while also reducing strain on the state’s grid.
The Long Road to 2028
PPAs are forward-looking deals. Tesla’s contract gives ContourGlobal the revenue certainty to finance construction, but no electrons will flow until the project is built and interconnected. Here’s the timeline, according to the developer:
- Major off-site construction (equipment sourcing, site preparation) began in 2025.
- On-site construction is scheduled to start in Q3 2026.
- First energization is targeted for Q3 2027.
- Commercial operations are expected in Q1 2028.
That’s a three-year build window, assuming no interconnection delays—a common pain point for large renewables. The WAPA interconnection study and securing CAISO delivery rights add bureaucratic hurdles, but ContourGlobal appears confident.
What This Means for Tech’s Energy Future
Tesla’s deal is part of a broader shift in corporate energy procurement. In the past decade, tech giants like Google, Amazon, and Microsoft have collectively signed tens of gigawatts of renewable PPAs. Those deals helped drive down solar costs, but they also exposed a flaw: solar-only contracts often deliver power when it’s least needed, requiring buyers to purchase additional, sometimes fossil-fueled, power at other hours. Adding batteries changes the equation.
Tesla’s own energy business sells Megapack batteries to developers and utilities, and it runs a virtual power plant program in Arizona with Salt River Project (SRP). Yet in this case, Tesla is neither the equipment supplier nor the grid operator—it’s simply a large customer. That’s notable. It means the company is willing to lock in long-term clean energy costs even when it doesn’t directly build the assets, suggesting it expects its electricity needs to keep growing.
Does this have a direct impact on the average Windows user? Not immediately. But indirectly, every kilowatt-hour that shifts from fossil fuels to renewables helps stabilize long-term electricity costs and reduces the carbon footprint of the products we use. For IT professionals managing on-premises data centers or cloud budgets, the takeaway is clear: renewable energy procurement is becoming more sophisticated, and storage-backed PPAs could become a template for achieving round-the-clock clean energy goals.
Key Takeaways for Energy Buyers
If you’re a business evaluating your own renewable energy strategy, Tesla’s move offers three lessons:
- Storage is no longer optional. A solar PPA without battery storage leaves your company exposed to price volatility during non-solar hours. Stacking a battery onto the contract can turn intermittent energy into a quasi-firm supply, making it easier to integrate with your load profile.
- Transmission access is critical. Sterling’s ability to reach the CAISO market adds tangible value. When siting renewable projects, don’t just look at solar irradiance—look at interconnection queues and export capacity to high-demand zones.
- Large buyers can shape projects. ContourGlobal reformulated Sterling specifically for Tesla. Early engagement with developers can lock in customized terms and lower per-unit costs.
What to Watch Next
Construction timelines and interconnection approvals will determine whether Project Sterling delivers on schedule. But the deal’s broader significance lies in its scale and structure. It signals that battery-backed solar is becoming the standard, not the exception, for large corporate energy purchases. Keep an eye on other tech manufacturers—Apple, Samsung, and chipmakers like TSMC—that face similar pressure to secure clean power for energy-intensive factories. If Tesla’s gamble pays off, expect a wave of hybrid PPAs to follow.