A power purchase agreement is not simply a cheaper replacement for a data center utility bill. A PPA may hedge an energy price or provide environmental attributes while the grid still charges for delivery, demand, system services and backup.
A useful comparison reconciles physical electricity delivery, contractual financial settlement and sustainability accounting before choosing which price belongs in the model.
What to include in the decision
- Distinguish onsite, physical and virtual PPAs
- Compare generation output to the load profile
- Do not erase utility charges from the comparison
- Stress-test contract obligations
Distinguish onsite, physical and virtual PPAs
An onsite PPA generally involves a third party owning generation installed at the customer location and selling its output to the customer. An offsite physical PPA involves remote generation and delivery arrangements that depend on local market structure.
A virtual PPA commonly settles financially against an agreed market reference; the facility still buys its operational electricity separately. The volume and timing of output are not automatically synchronized with 24-hour data center demand.
Compare generation output to the load profile
A site with 24/7 IT demand should model monthly and hourly production rather than assuming one contracted annual MWh amount covers every hour. Solar generation, for example, is intermittent, while load can stay high overnight.
Volume mismatch can create exposure to merchant prices, storage costs or residual utility supply. Include curtailment, congestion, basis risk and potential settlement differences where appropriate.
Do not erase utility charges from the comparison
The utility invoice may contain transmission, distribution, demand, standby, ancillary and fixed charges as well as purchased energy. Some components remain even when onsite assets reduce metered kWh.
A responsible business case states whether its PPA price is bundled or energy-only, where renewable certificates sit and which party is accountable for transmission and scheduling.
Stress-test contract obligations
Ask who carries construction delay, underproduction, credit, change-in-law, early termination and environmental-attribute delivery risk. A long contract can lock in price while also creating a large mark-to-market exposure.
For a data center planning multiple phases, align contract delivery dates and contracted generation with the actual energized IT capacity, not just the master-plan announcement.
Illustrative energy-only comparison
If 30,000 MWh annually are priced at $65/MWh under a hypothetical fixed PPA versus $90/MWh under a hypothetical energy supply rate, the simple energy difference is $750,000 per year (30,000 × $25). This does not establish an all-in saving: profile mismatch, transmission, demand charges, certificate value, settlement and credit risk must be evaluated separately.
A three-case procurement sensitivity test
The first case should use the utility-only tariff at the projected hourly load profile. The second adds a PPA with contracted output, basis or shape settlement and any retained utility charges. The third evaluates a delayed facility ramp, in which contracted production arrives before full load and excess energy or financial settlements must be managed.
For each case, compare annual cash cost, 95th-percentile monthly cost, collateral requirement and contract termination exposure. A PPA that improves the average annual price may still create higher short-term cash demands or mismatch risk under some market conditions.
Keep the environmental claims as a separate assessment. Energy cost savings and matching renewable electricity consumption across hours are not equivalent promises, and certificate treatment should be documented rather than inferred.
Why matching annual MWh is not enough
A continuously operating 50 MW facility consumes 50 × 24 = 1,200 MWh per day at that load. A hypothetical 10 MW solar project delivering five full-load-equivalent hours generates 50 MWh on that day, or about 4.2% of the facility’s daily consumption. That 4.2% is an energy comparison; it says nothing about guaranteed delivery at the hours the data center needs it.
In a virtual PPA, the offsite project and the data center commonly settle financially against market indices. The data center still buys physical grid power under its applicable supply and delivery arrangements. The project’s contracted strike price alone cannot determine the facility’s net electric cost without considering the market settlement and timing or basis differences.
For onsite third-party generation, specify who owns the interconnection, retains the environmental attributes, maintains the system and delivers energy during an outage. Even a physical onsite PPA is not automatically a 24/7 backup-power product.
Procurement model to compare
| Case | Include in cash model | Main uncertainty |
|---|---|---|
| Utility tariff only | kWh, kW, capacity and fixed charges | Escalation and load-shape changes |
| Offsite virtual PPA | Utility bill + contract settlements + fees | Market basis, hourly profile and credit |
| Onsite physical PPA | Purchased output + residual utility service | Availability, ownership and maintenance |
| Delayed project ramp | All above with lower initial load | Contracted output exceeds usable demand or hedge need |
Practical evaluation and governance
Compare hourly scenarios rather than using only annual average prices. Show a base case and stressed cases for a delayed data hall, low-price hours when generation is abundant, curtailment, counterparty default and termination. Contract review should cover settlement index, shape delivery, negative pricing, credit support and environmental certificate ownership.
Separately report expected annual spend, worst realistic monthly cash requirement and any emissions or renewable-matching claim. The latter needs its own methodology; an annual contract volume is not proof of hour-by-hour carbon-free operation.
Questions to ask before signing or building
- Is energy physically delivered to the facility or financially settled?
- Who owns energy attribute certificates and who can make a renewable claim?
- How does hourly generation align with 24/7 site load?
- Which utility charges remain payable and who bears basis risk?
Methodology: illustrative figures are deliberately separated from sourced claims. Utility rates, commercial charges and engineering performance must be validated against site documents. Publication date: October 19, 2026.
Research and technical references
- US DOE: Commercial Energy Financing Primer — background reference, not a project quotation
- US DOE: Evaluating Utility Rate Options — background reference, not a project quotation