What Is a Power Purchase Agreement? – PPAs for Large Energy Users
For a factory, a data center or a big campus, electricity is one of the largest costs on the books, and it rarely holds still. Utility rates change. Wholesale prices spike. Meanwhile, wind and solar developers need a buyer who will commit for years before a bank will lend them money. The contract that solves both problems at once is called a power purchase agreement. So what is a power purchase agreement, and how does it work for a large energy user?
A power purchase agreement (PPA) is a long-term contract in which a buyer agrees to purchase electricity, and often its renewable energy certificates, from a specific power project at a set price for a set number of years. The buyer, called the offtaker, gets price certainty and, for renewable projects, a credible claim to clean energy.
The seller, usually a project developer, gets a predictable revenue stream it can use to finance construction. Terms commonly run 10 to 20 years. PPAs come in two main forms: physical contracts, where the power is actually delivered, and financial ones, where the parties settle the difference between the contract price and the market price.
How Does a Power Purchase Agreement Work?
A power purchase agreement works by locking in the price for output from a specific project. The developer builds and operates the plant. The buyer pays the agreed price for each MWh the contract covers, for the life of the deal.
Here's the basic flow for a typical renewable PPA:
- The buyer and developer negotiate price, term, volume, delivery point and who keeps the renewable energy certificates (RECs).
- The developer uses the signed contract, along with equity and tax benefits, to raise construction financing.
- The project is built and starts producing power.
- Each month, the buyer pays for the contracted output at the agreed price, and RECs transfer to the buyer.
- At the end of the term, the contract expires, and the project may sign a new deal or sell into the market.
The financing step is the reason PPAs exist in their current form. Lenders want to see contracted revenue before they fund a large project. A creditworthy buyer's long-term commitment is often what makes the project bankable.
What Are the Key Terms in a PPA?
The key terms in a PPA define price, quantity, timing and who carries which risks. These matter most:
- Price: fixed, fixed with an annual escalator, or indexed to something else.
- Term: usually 10 to 20 years for new renewable projects.
- Volume: "as-generated" (whatever the plant produces) or a fixed shape (a set amount in each hour or block).
- Delivery or settlement point: where on the grid the power is delivered or priced.
- Environmental attributes: who gets the RECs and other credits.
- Curtailment: who pays when the grid operator tells the plant to cut output.
- Credit support: letters of credit or guarantees from both sides.
- Termination and change in law: what happens if either side fails or rules change.
Each term moves risk from one party to the other. A buyer who accepts as-generated volume takes on weather risk. A seller who agrees to a fixed shape takes on the job of filling gaps when its plant isn't producing.
What Is the Difference Between Physical and Virtual PPAs?
The difference is whether electricity actually flows to the buyer under the contract. In a physical PPA, the buyer takes delivery of the power at a defined point on the grid and uses it, usually through a retail supplier or as a wholesale market participant. The US Environmental Protection Agency notes that physical PPAs are mostly limited to competitive power markets and are used largely by big, investment-grade buyers.
A financial PPA works differently. The buyer keeps buying power from its local utility as usual. Separately, the buyer and project settle the difference between the fixed contract price and the market price the project receives. The buyer still gets the RECs. Our explainer on the virtual PPA walks through that settlement math in detail.
There are other variations. In a "sleeved" PPA, a utility or retailer delivers the project's power to the buyer for a fee. In an on-site PPA, a third party owns equipment like solar panels on the buyer's property and sells the output directly to the buyer.
How Much Power Does a PPA Cover?
A PPA covers whatever share of a project's output the parties negotiate, and the volume math is simple once you know the project's capacity factor. Take a hypothetical as-generated solar PPA:
- Project size: 100 MW
- Assumed capacity factor: 25% (typical for solar in sunny regions)
- Annual output: 100 MW × 8,760 hours × 0.25 = 219,000 MWh
- Illustrative contract price: $35/MWh
- Annual payment: 219,000 × $35 = $7,665,000
Now compare that with a facility that runs at a steady 25 MW around the clock: 25 × 8,760 = 219,000 MWh a year. The yearly totals match, but the timing doesn't. The solar plant produces at midday and nothing at night, while the facility uses power every hour. That timing gap is called shape risk, and it's one of the biggest things buyers underestimate.
How Is a PPA Price Set?
A PPA price is set by negotiation, but it's anchored by what the developer needs to cover its costs and earn a return. For a wind or solar project with no fuel cost, the price mostly reflects the upfront investment spread over the expected output.
The biggest drivers are:
- Capital cost: panels, turbines, inverters, land, interconnection and construction.
- Capacity factor: a sunnier or windier site spreads the same cost over more MWh, lowering the price.
- Tax incentives: federal credits can reduce the price a developer needs, where they apply.
- Interest rates: higher borrowing costs raise the required price.
- Term: a longer contract spreads costs over more years and usually lowers the price.
- Escalator: a contract that rises a little each year can start lower than a flat one.
- Risk allocation: the more risk the seller carries (shape, curtailment, basis), the higher the price it will ask.
That last point is often missed. Two PPAs at different prices may not be comparable at all if one shifts more risk to the buyer. Compare the whole package, not just the headline number.
Why Do Large Energy Users Sign PPAs?
Large energy users sign PPAs for three main reasons: price stability, clean energy goals and influence over what gets built. A fixed price for 15 years makes budgeting easier, especially for operations where power is a top cost.
Companies with renewable energy targets use PPAs because they can be tied to specific new projects. Many buyers value "additionality," the idea that their contract caused a new project to be built rather than just buying credits from an existing one. A PPA that finances a new plant makes that claim much stronger than an unbundled REC purchase.
PPAs can also make economic sense on their own. When long-term renewable prices are lower than expected future market prices, a PPA can save money over its life. It can also lose money if market prices fall, which is why buyers should treat it as a hedge, not a guaranteed saving.
What Are the Risks of a Power Purchase Agreement?
The main risks of a power purchase agreement are price, timing, location and counterparty risk. Each one deserves attention before signing:
- Market price risk: if wholesale prices fall below the contract price for years, the buyer overpays relative to the market.
- Shape risk: output may not match the buyer's hourly use.
- Basis risk: the price at the project's location can differ from the price where the buyer uses power, often because of transmission congestion.
- Curtailment risk: grid limits may force the project to cut output.
- Counterparty risk: either side could fail to perform or go bankrupt.
- Accounting and regulatory risk: some contracts are treated as derivatives, and rules can change.
None of these risks is a reason to avoid PPAs. They're reasons to model the deal carefully, with realistic price scenarios, before committing to a decade or more.
Can You Sign a PPA in a Regulated Utility Territory?
Often not directly, at least for physical delivery. In states where a single regulated utility holds the exclusive right to sell power to retail customers, a buyer usually can't buy power straight from a third-party generator. Options there include utility green tariffs, utility-arranged sleeved deals or financial PPAs with projects in competitive markets elsewhere.
Rules vary widely by state, so check with the utility, the state regulator and experienced counsel before planning around a specific structure. Projects that need firm, around-the-clock power may also compare a PPA against owning on-site generation, which is a different decision with its own levelized cost of energy math.
A Power Purchase Agreement Trades Flexibility for Certainty
So what is a power purchase agreement? It's a long-term deal that trades flexibility for certainty on both sides. The buyer locks in a price and a clean energy claim. The developer gets the contracted revenue it needs to finance and build.
The value of a PPA lives in the details: price, volume shape, delivery point, curtailment rules and credit terms. A good contract matches the buyer's real load and risk appetite. A bad one can turn into a 15-year headache.
Before you talk price with anyone, pull a year of your own interval meter data. Knowing your hourly load tells you how much shape risk you can live with, and that answer points you toward physical delivery or a financial hedge. Get an independent price forecast, and run the contract past qualified legal and tax advisors, since nothing here is legal, tax or investment advice.