Fixed-Price vs Indexed PPA
Definition
A fixed-price PPA sets the price per megawatt-hour for the contract term, either flat or rising by a set escalator each year. An indexed PPA ties the price, in whole or in part, to a moving reference: a wholesale market price, an inflation index or a commodity price. The choice decides who bears changes in power prices and costs: under a fixed price the project gives up upside and the buyer gives up the benefit of falling prices; under an index, the project's revenue moves with the reference.
Why it matters
Investors in a contracted project usually assume the price is fixed. If it is indexed, revenue and debt service coverage move with the index, and a downturn in the index can cut cash flow even when output is normal. Reading the price clause, and any floors, caps or escalators, shows how much price risk the project still carries.
Common misconceptions
- •A fixed price is not inflation-protected unless it escalates in line with costs.
- •An indexed PPA is not a merchant contract; volume and term can still be fixed while price moves.
- •A floor or cap changes the risk materially; read the whole price formula, not the starting price.
- •The label is only a starting point. Investor outcomes usually depend on the governing documents, cash-flow priority, valuation policy, disclosure quality, and manager discretion surrounding the term, not just the shorthand definition used in marketing materials.
Technical details
Common price structures
Flat fixed price for the term.
Fixed price with an annual escalator (for example a set percentage).
Market-indexed: a hub price plus or minus a spread, sometimes with a floor.
Inflation-indexed: price adjusted by a consumer or producer price index.
Commodity-indexed: price tied to the buyer's product, such as aluminum.
Worked example: Century Aluminum, 2025 10-K
Grundartangi: power from Landsvirkjun, Orkuveita Reykjavikur and HS Orka through 2026 to 2036; about 70% 'fully-indexed to the price of primary aluminum,' described as 'a natural hedge of one of our largest production costs.'
Sebree (Kentucky): all power 'under a market-based power agreement' through May 31, 2028.
Mt. Holly (South Carolina): Santee Cooper supplies all power through 2031 at cost-of-service rates.
How investors apply the term
Investors usually apply this term by tying the definition back to the controlling documents and then asking which cash flows, rights, restrictions, or valuation assumptions it changes. A useful review looks at the term alongside fees, leverage, liquidity, reporting frequency, and manager discretion rather than treating it as a standalone concept.
The practical diligence test is simple: identify who benefits if the assumption is wrong, who has control when conditions change, and what evidence the investor receives after closing. Terms that cannot be reconciled to documents, cash movements, and monitoring data should be treated as marketing shorthand until proven otherwise.
Frequently asked questions
- Do fixed-price PPAs rise over time?
- Often. The EPA notes that many physical PPAs 'include a price escalator,' generally below historic increases in utility rates. An escalator protects the project against cost inflation only to the extent it matches actual costs.
- What can a PPA be indexed to?
- A wholesale power price at a hub, an inflation index, or the buyer's own product price. Century Aluminum's Grundartangi smelter in Iceland buys about 70% of its power at rates 'fully-indexed to the price of primary aluminum,' and about 30% at 'a fixed price with an additional LME-linked component,' under contracts running to 2026 to 2036.
- Why would a seller accept an index tied to the buyer's product?
- To win a large, long-term buyer whose ability to pay depends on its product price. The seller takes on commodity risk in exchange; when the index falls, so does its revenue.