Physical and Virtual PPAs: Two Structures, One Purpose

A power purchase agreement is a long-term contract between a buyer and a generator that fixes the terms on which the buyer will purchase the generator's electricity or its associated environmental attributes. The contract typically runs ten to twenty years, and that duration is not incidental — it is the whole point. A renewable project is enormously expensive to build and cheap to run, which means almost all of its cost is upfront. To finance that upfront cost, a developer must convince a lender that revenue will flow reliably for many years. A short contract cannot do that. A fifteen-year commitment from a creditworthy buyer like a large technology company can, and that is why the PPA is the instrument that actually causes new generation to be built.

There are two broad structures, and understanding the difference is essential. The first is a physical PPA. Here the buyer actually takes delivery of the electricity, or arranges for it to be delivered into the grid on its behalf, and the power flows through the same market and transmission system that serves its facilities. Physical PPAs make the most sense when the buyer's load and the generator sit inside the same grid region, so the electricity can plausibly serve that load. The buyer receives both the energy and the certificates, and the arrangement is relatively intuitive: you are buying power from a specific plant and using it.

The second structure is the virtual PPA, sometimes called a financial or synthetic PPA, and it is the workhorse of corporate clean procurement precisely because it is more flexible. In a virtual PPA, no electricity physically changes hands between the generator and the buyer. Instead the two parties enter a financial arrangement, structured as what is called a contract for differences. The generator sells its electricity into the wholesale market at whatever the market price happens to be. The buyer and generator have agreed on a fixed reference price, often called the strike price. If the market price the generator receives is below the strike price, the buyer pays the generator the difference. If the market price is above the strike price, the generator pays the buyer the difference. The net effect is that the generator is guaranteed a stable, predictable price regardless of market swings — which is exactly the bankable revenue the lender needs to see. The buyer, in exchange, receives the environmental certificates and takes on the financial ups and downs of the market price.

Why would a buyer prefer this seemingly convoluted arrangement? Because it decouples the clean-energy purchase from the physical logistics of delivering power. A data-center operator in Virginia can sign a virtual PPA with a wind farm in Texas without needing any way to physically move electrons across half a continent. The wind farm sells into the Texas market, the operator settles the financial difference, and the operator collects the certificates to back its clean-energy claim. This flexibility is why virtual PPAs dominate large corporate renewable procurement: they let buyers finance new projects wherever the wind blows hardest or the sun shines longest, unconstrained by the location of their own facilities.

But that same flexibility exposes the limitation we flagged in the additionality discussion. A virtual PPA proves additionality — the project got built because of the buyer's commitment — but it says nothing about whether the clean generation lines up in time or place with the buyer's actual consumption. The Virginia data center running at midnight is drawing on the local grid's midnight resources, which the distant Texas wind farm does nothing to clean. The buyer can honestly claim to have financed new wind, and can honestly hold certificates equal to its annual consumption, while its real-time physical footprint remains stubbornly tied to whatever its local grid is burning at any given hour. This is the seam that the more demanding matching frameworks are designed to close, and it is worth carrying the tension forward rather than resolving it too early.

One more practical dimension deserves mention: risk. A virtual PPA is a financial position, and financial positions can move against you. If wholesale power prices fall for years — because natural gas gets cheap, say, or because so much solar gets built that midday prices collapse — the buyer can find itself paying out the difference year after year, effectively subsidizing the project more than it expected. Conversely, if prices rise, the buyer collects. Corporate buyers have learned, sometimes painfully, that a PPA is not a simple green purchase but a long-dated commodity hedge with an environmental attribute stapled to it. Faraday's read: this is why serious procurement teams include people who think like traders, not just people who think like sustainability officers. The instrument that finances the cleanest new wind farm in the country is also a multi-decade bet on power prices, and pretending otherwise is how organizations get surprised.