Power Purchase Agreement (PPA)

A power purchase agreement (PPA) is a long-term contract in which a buyer agrees to purchase electricity from a specific generator, or the financial equivalent of that electricity, at a price and on terms fixed in advance, typically for 10 to 25 years. The seller is usually the owner of a power plant, increasingly a wind or solar farm; the buyer may be a utility, a large company, a public body or, in residential solar, a homeowner.

PPAs exist mainly to make new power plants financeable. Lenders are more willing to fund a project when its revenue is contracted with a creditworthy buyer, so a PPA turns uncertain future electricity sales into something closer to a predictable income stream. For buyers, PPAs offer price certainty and, when the plant is renewable, the environmental attributes of the power, usually in the form of renewable energy certificates.

Imagine a bakery that agrees to buy all its flour from one farmer for the next fifteen years at a fixed price. The farmer can now borrow money to buy a new field and tractor, because the bank can see who will buy the crop. The bakery no longer worries about flour prices jumping, though it might end up paying more than the market if prices fall.

A PPA does the same with electricity. A company, a utility or a household agrees to buy the output of a solar or wind farm for many years. The developer uses that promise to raise money and build the plant, and the buyer gets a known price and a claim to clean power.

PPAs fall into a few broad families:

• Utility PPAs. The traditional form, in which a regulated utility buys power from an independent producer to supply its customers. In the United States, utilities have been required since the Public Utility Regulatory Policies Act of 1978 to buy power from certain qualifying facilities.
• Physical corporate PPAs. A company buys electricity directly from a generator and takes delivery through the grid, either on-site or through a "sleeved" arrangement in which a utility or supplier delivers the power and passes it through. These are common where retail markets allow customers to choose suppliers.
• Virtual or financial PPAs. The buyer never takes the electricity. The generator sells its power into the wholesale market, and the two sides settle the difference between the market price and a fixed "strike" price, while the buyer receives the certificates. This works like a contract for difference or a fixed-for-floating swap, one of the derivatives used in commodity markets, and is a form of hedging.
• Residential solar PPAs. In the third-party-ownership model, a solar company installs panels on a home, owns and maintains them, and sells the electricity they produce to the homeowner at a set rate per kilowatt-hour, often with an annual escalator, for about 20 to 25 years. A solar lease is similar but charges a fixed monthly fee instead of a per-kilowatt-hour price.

In a virtual PPA, settlement each period is the difference between the market price and the strike price, multiplied by the volume generated:

• $P_{\text{market}}$ is the wholesale price at the agreed settlement point, per megawatt-hour (MWh).
• $P_{\text{strike}}$ is the fixed price in the contract.
• $Q$ is the volume of electricity the project produced in the period, in MWh.

For example, if the strike price is $50 per MWh, the market price averages $60 and the plant produces 10,000 MWh in a month, the generator pays the buyer $(60 - 50) \times 10{,}000 = 100{,}000$, that is $100,000. If the market averages $40 instead, the buyer pays the generator $100,000. Either way, the generator ends up with an effective $50 per MWh, while the buyer's net cost of power is roughly fixed, much as in a forward contract.

The main risks include:

• Price risk. If market prices fall well below the strike, the buyer makes ongoing payments, which may need to be marked to market and, under US GAAP and IFRS, can be accounted for as a derivative unless an exemption applies, making hedge accounting relevant.
• Basis and shape risk. The project's settlement point and generation profile may differ from where and when the buyer consumes power, a form of basis risk.
• Volume risk. Wind and solar output varies with the weather, which some contracts address with fixed-shape or "baseload" structures and others with weather derivatives.
• Credit risk. Each side depends on the other paying for decades, so counterparty risk is managed with credit ratings, guarantees and collateral.

Corporate PPAs became a major route in sustainable finance and a common way for companies to meet renewable electricity commitments and to report lower market-based Scope 2 emissions under the Greenhouse Gas Protocol. Contracted project revenue often supports green bonds and project loans. Institutional owners such as members of the Net-Zero Asset Owner Alliance (NZAOA) count such projects towards transition-financing goals, and buyers often cite PPAs as part of their response to the Paris Agreement and in corporate responsibility reporting. Banks such as JPMorgan, through its Center for Carbon Transition (CCT), have advised clients on structuring them.

Critics argue that virtual PPAs and certificate purchases can let companies claim "100% renewable" while their actual consumption is supplied by fossil plants at other hours, which has prompted interest in hourly, location-matched procurement. Residential solar PPAs have drawn consumer complaints about long terms, price escalators, and difficulties selling homes with contracts attached and some US state attorneys general have taken action against misleading solar sales practices. Homeowners in a PPA also generally do not own the system or claim the related tax credits, which go to the system owner.

• US EPA: Physical Power Purchase Agreements
• US Department of Energy: Homeowner's Guide to Going Solar