PPA vs. Merchant Revenue
Executive Summary
Key Takeaways
- ✓ PPA revenue is set by an agreed formula largely insulated from market price movements; merchant revenue is sold at prevailing market price, carrying genuine, undetermined price risk.
- ✓ PPA revenue carries counterparty (offtaker credit) risk as its primary risk driver; merchant revenue carries market price risk as its primary driver — different risk types requiring different mitigation and disclosure.
- ✓ A project's actual revenue is frequently a blend of both — a PPA for a defined tenor, followed by a merchant tail — and each component should be modelled and, where a DCF is used, discounted separately.
- ✓ Debt sizing and lender comfort are typically materially higher for PPA-backed revenue than for merchant revenue, given the difference in cash flow predictability each provides.
- ✓ Blending PPA and merchant revenue into a single revenue-per-unit assumption is a common construction error that conceals the project's actual exposure to market price risk and misstates achievable debt capacity.
Objective¶
This comparison sets out the differences between power purchase agreement (PPA) contracted revenue and merchant power revenue, within Energy Revenue Models.
Side-by-Side Comparison¶
| Dimension | PPA Revenue | Merchant Revenue |
|---|---|---|
| Pricing basis | Agreed contractual formula | Prevailing market price |
| Primary risk | Offtaker counterparty (credit) risk | Market price risk |
| Cash flow predictability | High, subject to contract terms | Low, dependent on market conditions |
| Typical debt sizing implication | Supports higher debt sizing and more conservative coverage | Requires more conservative sizing or structural protection |
| Modelling basis | Contract's pricing formula, volume structure, and escalation | Independent forward price curve and sensitivity range |
Why the Distinction Matters for Debt Sizing¶
Lenders typically extend more debt capacity against PPA-backed revenue than against merchant revenue at the same nominal cash flow level, because PPA revenue's contractual pricing gives materially more confidence in sustained debt service coverage across the debt tenor. Merchant revenue's price uncertainty means the same nominal revenue figure carries a wider range of plausible outcomes, which a lender typically addresses through more conservative sizing, a shorter tenor, or additional structural protection such as a cash sweep.
The Common Blended Structure¶
Many projects carry both revenue types across their life — most commonly a PPA for a defined initial tenor followed by a merchant tail once the PPA expires, or a partial PPA covering only a portion of output with the remainder sold merchant throughout. In either case, each component should be modelled, and where a discounted cash flow valuation is used, typically discounted, separately — applying a single blended discount rate or price assumption across both components understates the risk premium the merchant-exposed portion actually carries.
Common Construction Pitfalls¶
Blended revenue-per-unit assumption. Combining PPA and merchant revenue into a single price assumption conceals the project's actual exposure to market price risk.
Single discount rate applied to both. Where a DCF is used, applying one blended discount rate across contracted and merchant-exposed cash flow understates the merchant portion's genuine risk premium.
Debt sized against blended revenue without differentiation. Sizing debt against a combined revenue figure without reflecting the materially different coverage confidence each component provides can overstate sustainable debt capacity.
Continue Reading¶
Prerequisites¶
- Energy Revenue Models — the parent guide
- Power Purchase Agreement (PPA) Modelling
- Merchant Power Models
Related Glossary¶
How OXXON tests thisRun a free structural check with FMAE
Frequently Asked Questions
What is the core difference between PPA and merchant revenue?
PPA revenue is set by an agreed contractual formula, largely insulated from market price movements subject to the contract's own terms; merchant revenue is sold at prevailing market price with no fixed contract, carrying genuine, undetermined price risk dependent on future market conditions.
What is the primary risk driver for each revenue type?
PPA revenue's primary risk driver is counterparty (offtaker credit) risk — whether the offtaker can and will pay under the contract; merchant revenue's primary risk driver is market price risk — what price the project will actually realize when it sells into the market.
Can a project have both PPA and merchant revenue?
Yes, commonly — a PPA covering a defined initial tenor, followed by a merchant tail once the PPA expires, or a partial PPA covering only a portion of output with the remainder sold merchant — each component should be modelled, and where a DCF is used, typically discounted, separately given their different risk profiles.
Why does debt sizing typically favor PPA-backed revenue?
Because PPA revenue's greater cash flow predictability gives lenders more confidence in debt service coverage across the debt tenor, whereas merchant revenue's price uncertainty introduces coverage ratio volatility that typically requires more conservative debt sizing or additional structural protection.
What is the most common error in modelling projects with both revenue types?
Blending PPA and merchant revenue into a single revenue-per-unit assumption, which conceals the project's actual exposure to market price risk and can materially misstate the debt capacity a lender would actually be willing to size against the project's true, risk-differentiated cash flow.
Related Articles
Energy Revenue Models
A power project's electricity revenue is rarely a single price applied to total output — it is typically a stack of contracted (PPA), capacity, and merchant components, each with its own price-setting mechanism and risk profile. This guide covers how to build that revenue stack as separately priced, explicitly modelled modules, and how to combine them into a single reconciled revenue output without losing the visibility each component requires.
Power Purchase Agreement (PPA) Modelling
A power purchase agreement is rarely a single flat price for the life of a project — it typically carries a specific pricing formula, a defined volume structure (take-or-pay versus as-available), a tenor shorter than the asset's full operating life, and its own escalation mechanics. This guide covers how each of these PPA components should be built explicitly into a power project financial model, and how the model should represent the transition once the PPA expires.
Merchant Power Models
Merchant power revenue is sold at prevailing market price rather than under a fixed-price contract, carrying genuine, undetermined price risk that a static assumption understates. This guide covers how to build merchant exposure into a power project model: constructing a forward price curve, testing an explicit sensitivity range around it, representing any hedging arrangement, and modelling the merchant tail that follows PPA or contract expiry.
Merchant Tail
The merchant tail is the period following power purchase agreement or other contract expiry during which a power project sells its output at prevailing merchant market price rather than a fixed contracted price. It carries materially higher revenue risk than the preceding contracted period and should be modelled as its own explicit period with its own price assumption and discount rate.