Mechanical Completion to COD: Fox Run Has a 24-Day Contract Gap Worth $1.43 Million
Fox Run Solar survives its interconnection process and finally reaches construction.
Now the project team starts using a familiar sentence:
"We should be complete by the end of June."
That sentence is not precise enough to finance.
Give Fox Run the following illustrative timeline:
Mechanical Completion 10-Jun
EPC Substantial Completion 28-Jun
Guaranteed PPA COD 1-Jul
IA / grid commercial operation 25-Jul
Actual PPA COD 25-Jul
Tax-equity final funding 5-Aug
Term conversion 15-Aug
EPC Final Completion 30-Sep
Nothing in that schedule is contradictory.
The project can be mechanically complete on June 10, substantially complete under one EPC definition on June 28, late under the PPA from July 2, physically unable to achieve commercial grid operation until July 25, and still remain "in construction" for financing purposes until August 15.
Those are not six names for the same date.
They are six different contractual tests.
Start with the definitions, not the industry vocabulary
Mechanical Completion, Substantial Completion and Commercial Operation Date sound standardized.
They are not.
Recent filed EPC contracts make the point cleanly.
The Axial Basin Solar EPC filed with the SEC makes Commercial Delivery of Power a condition to Substantial Completion. Its commercial-delivery definition includes, among other things, testing required for commercial delivery, initial synchronization at the point of interconnection, placed-in-service status and required inspections.
That means its Substantial Completion milestone is already downstream of actual commercial power delivery.
Other contracts can draw the line earlier.
A project-finance model therefore should never assume:
Mechanical Completion
→ Substantial Completion
→ COD
as a universal legal sequence.
The actual sequence is whatever the contracts define.
Fox Run's Mechanical Completion is a physical-construction gate
For the running example, assume Fox Run's EPC defines Mechanical Completion as the point when the major plant systems are physically installed and ready to enter final energization / commissioning activities, but commercial export has not yet been achieved.
So on June 10:
Major equipment installed YES
Collection system complete YES
Project substation substantially complete YES
Commercial export NO
PPA COD NO
Debt conversion NO
Mechanical Completion is meaningful.
It can trigger:
- milestone payments;
- owner / IE certification;
- commissioning rights;
- tax-equity or bridge funding conditions;
- release of some contractor obligations; or
- movement into the next phase of testing.
It is still not revenue.
A model that treats Mechanical Completion as COD has converted physical progress into cash before the contracts do.
Substantial Completion is where the risk allocation starts to matter
Assume Fox Run's EPC is written so that Substantial Completion can occur once:
- Mechanical Completion is achieved;
- performance testing is passed;
- punch-list work is below an agreed threshold;
- owner-side permits and contractor deliverables are complete; and
- the contractor has completed the grid-interface work within its own EPC scope.
But assume the definition does not require final transmission-owner commercial-operation authorization.
Fox Run therefore reaches EPC Substantial Completion on June 28.
At that date, assume:
EPC schedule-LD clock stops
Retainage partly released
Performance security steps down
Warranty period begins
Care / custody / control shifts per EPC
Final punch-list obligations remain
The transmission owner's final grid condition is still open.
That is the interface gap.
The PPA asks a different question
Fox Run's PPA does not care that the EPC contractor has satisfied its own Substantial Completion definition.
The PPA cares whether the seller can perform the contracted delivery obligation.
Assume the Guaranteed COD is July 1.
Actual PPA COD requires:
- the plant to be complete enough for commercial operation;
- metering in service;
- required testing completed;
- interconnection / grid authorization;
- relevant permits and notices; and
- any other defined PPA conditions.
The grid-side condition is not satisfied until July 25.
So:
Guaranteed PPA COD 1-Jul
Actual PPA COD 25-Jul
Delay period 24 days
The EPC contractor can be "done" for Substantial Completion purposes while the PPA seller is late.
That is sponsor interface risk.
The 24-day gap is worth $1.43 million in the teaching case
Put money on the dates.
Assume:
Illustrative PPA delay damages $25,000/day
Average construction debt outstanding $180m
Construction debt rate 7.0%
PPA delay period 24 days
PPA delay damages:
24 × $25,000
= $600,000
Additional debt carry:
$180m × 7% × 24 / 365
≈ $828,000
Combined sponsor exposure:
PPA delay damages $0.600m
Additional debt carry 0.828m
-------
Illustrative exposure $1.428m
That number exists even though:
EPC Substantial Completion = achieved
Plant physical construction = largely complete
The financing risk lives in the days between documents.
Now change only the EPC definition
Keep every physical fact the same.
Create Contract A and Contract B.
Contract A — commercial delivery is required for EPC Substantial Completion
This resembles the structure visible in the Axial Basin filing.
Under the simplified example:
Grid commercial operation 25-Jul
EPC Substantial Completion 25-Jul
The EPC schedule-remedy clock can potentially continue through the grid-delay period, subject to:
- causation;
- contractor responsibility;
- force majeure / owner relief;
- grid-risk allocation;
- extension-of-time rights;
- sole-remedy language; and
- the LD cap.
Assume, purely for teaching, EPC delay LDs would otherwise accrue at:
$30,000/day
for the same 24 days.
Gross EPC LD amount:
24 × $30,000
= $720,000
The sponsor's $1.428 million exposure is now partially matched by a possible $720,000 EPC recovery.
Before caps and other limitations:
Sponsor exposure $1.428m
Potential EPC LD recovery (0.720m)
-------
Illustrative uncovered amount $0.708m
Contract B — grid-side commercial authorization is outside EPC Substantial Completion
Fox Run reaches EPC Substantial Completion on June 28.
EPC delay LDs stop.
PPA COD remains July 25.
Now the same grid delay leaves the sponsor with the full illustrative:
$1.428m
unless another agreement transfers it.
Same plant.
Same grid delay.
Different definition.
Different financing result.
"Who caused the delay?" matters more than the milestone name
The Contract A comparison above is deliberately incomplete.
An EPC definition can require commercial delivery and still give the contractor schedule relief for delays caused by:
- the owner;
- the transmission provider;
- force majeure;
- permit authorities;
- grid outages;
- buyer conditions; or
- other excusable-delay events.
So the model should not use:
Substantial Completion late
→ EPC LDs owed
It should use:
Milestone missed
↓
What caused the delay?
↓
Is the cause contractor-risk?
↓
Was time relief available / properly claimed?
↓
LD amount
↓
cap / security / sole-remedy analysis
Part 2 of this series is about that waterfall.
Part 1 is about getting the milestone clock right before calculating a dollar.
PPA COD and IA Commercial Operation can be the same date and still be separate conditions
In Fox Run's base case:
IA commercial operation 25-Jul
PPA COD 25-Jul
Keep them in separate model cells anyway.
The IA asks whether the project has satisfied the transmission-provider / interconnection conditions for the relevant operating status.
The PPA asks whether the seller has satisfied the contractual commercial-operation definition.
They can coincide.
They do not become the same defined term.
A missing PPA notice can delay PPA COD without moving the grid authorization.
A grid test can delay IA commercial operation and therefore PPA COD.
The direction of dependency depends on the documents.
A good model should show the dependency rather than infer it from two equal base-case dates.
Backfeed and initial energization can happen even earlier
Fox Run can receive backfeed before it can export commercial power.
That can allow:
- inverter commissioning;
- tracker commissioning;
- transformer testing;
- BESS charging;
- SCADA testing; and
- auxiliary systems
to proceed.
So the construction schedule may look like:
Backfeed available 25-May
Mechanical Completion 10-Jun
Initial project energization 15-Jun
EPC performance testing 20-Jun
EPC Substantial Completion 28-Jun
IA commercial operation 25-Jul
PPA COD 25-Jul
Collapsing those into "energization" destroys useful schedule logic.
For BESS, the distinction can be even more important because import rights and charging availability can be prerequisites to performance testing.
PPA COD is not necessarily financing completion
Fox Run begins earning contracted revenue on July 25.
The construction financing is still not done.
Assume tax-equity final funding occurs August 5.
Assume term conversion occurs August 15.
The 21 days between PPA COD and term conversion can still carry:
- construction-loan pricing;
- completion support;
- undrawn reserve requirements;
- hedge conditions;
- completion certificates;
- lien releases;
- debt-service tests; and
- sponsor contingent obligations.
So a financing model should not use:
Construction loan ends at COD
unless the credit agreement actually says so.
For Fox Run:
PPA COD 25-Jul
Term conversion 15-Aug
Gap 21 days
That gap is another financing period with its own cost and conditions.
Tax-equity funding can have yet another completion definition
Tax-equity documents can use Mechanical Completion, Substantial Completion, placed-in-service status, tax opinions, appraisals, partnership conditions and project-document deliverables in combinations that differ from the EPC and PPA.
A 2026 SEC-filed tax-equity amendment shows exactly why these dates should stay separate: Mechanical Completion, Substantial Completion, PPA COD and interconnection milestones can each be tracked as distinct funding conditions.
The model should therefore have:
Tax-equity initial funding
Tax-equity mechanical-completion funding
Placed-in-service funding / true-up
Final funding
where applicable.
Do not infer investor funding from EPC milestone names alone.
Final Completion can still control real cash
Fox Run's EPC reaches Final Completion on September 30.
That date can control:
- completion of remaining punch-list items;
- final lien releases;
- as-built drawings and manuals;
- final permits / close-outs;
- final milestone payment;
- release of retainage;
- security release; and
- remaining contractor default rights.
A project can therefore be:
Producing revenue YES
PPA COD YES
Term converted YES
EPC finally complete NO
for weeks or months.
That matters if retainage or contractor security is the sponsor's remaining leverage over unfinished work.
The project schedule should not simply disappear after COD.
Build one milestone matrix before building the delay model
Fox Run's core completion matrix should look like this:
| Milestone | Primary document | Illustrative date | What changes |
|---|---|---|---|
| Backfeed | Utility / IA process | 25-May | Commissioning power available |
| Mechanical Completion | EPC | 10-Jun | Physical construction gate |
| EPC Substantial Completion | EPC | 28-Jun | EPC schedule remedies / payment / risk shift |
| Guaranteed COD | PPA | 1-Jul | PPA lateness starts |
| IA Commercial Operation | IA | 25-Jul | Grid operating right |
| Actual PPA COD | PPA | 25-Jul | Contracted revenue begins |
| Tax-equity final funding | Tax equity | 5-Aug | Investor cash / true-up |
| Term conversion | Credit agreement | 15-Aug | Construction debt transitions |
| EPC Final Completion | EPC | 30-Sep | Final contractor close-out |
The dates are teaching assumptions.
The structure is not.
Every live deal should have this table.
The schedule needs dependency arrows, not just dates
A model with nine separate dates can still be wrong if it does not show which dates depend on which others.
For Fox Run:
Backfeed
→ commissioning tests
Mechanical Completion
→ final energization / testing work
IA Commercial Operation
→ one PPA COD condition
PPA COD
→ revenue start
Tax-equity final funding
→ debt repayment / funding source
Term conversion
→ release or reduction of sponsor completion support
Final Completion
→ retainage / security release
When the transmission-owner date moves, the model can then propagate only the milestones that actually depend on it.
That is much better than:
COD +30 days
Tax equity +45 days
Term conversion +60 days
with fixed offsets that have no contractual basis.
The completion risk is the mismatch between remedy clocks
Return to the June / July gap.
PPA clock
Guaranteed COD 1-Jul
Actual COD 25-Jul
PPA delay 24 days
EPC clock under Contract B
Substantial Completion 28-Jun
EPC delay clock stops 28-Jun
The sponsor has a period where:
PPA remedy clock = running
EPC remedy clock = stopped
That is the uncovered interface.
Under Contract A, if the contractor remains responsible and no time relief applies:
PPA remedy clock = running
EPC remedy clock = also running
Now the sponsor has an offsetting remedy, subject to the next article's limitations.
A contract review should search for these periods explicitly.
The word "completion" by itself does not reveal them.
The lender's completion definition should be built from the cash waterfall backward
The credit agreement needs its own completion test because the lender cares about a different question:
Is the project stable enough to move from construction risk to operating risk?
That can require more than PPA COD.
For Fox Run, a sensible financing checklist might include, depending on the actual deal:
- PPA COD achieved;
- IA operating status achieved;
- tax-equity funding received;
- no material construction defaults;
- reserve accounts funded;
- final title / lien / insurance items delivered;
- minimum performance / output test;
- completion certificates;
- hedge conditions;
- projected DSCR / sizing condition; and
- no outstanding issue requiring sponsor completion support.
That is why term conversion occurs August 15 in the teaching case rather than July 25.
The lender is not redefining COD.
It is testing a different risk transition.
The diligence questions are now document-specific
For every Fox Run milestone:
- What document defines it?
- What exact conditions are included?
- Who certifies it?
- Can conditions be waived, and by whom?
- Does the milestone require interconnection or commercial delivery?
- Which party controls those conditions?
- Does delay in a third-party condition give the EPC contractor time relief?
- What remedy starts or stops at the milestone?
- What payment or retainage moves?
- Does warranty start?
- Does care / custody / control transfer?
- Does security step down?
- Does tax-equity funding depend on it?
- Does term conversion depend on it?
- Is there a long-stop date after it?
- What evidence does the lender require?
The model should contain the dates.
The closing checklist should contain the evidence.
The contract summary should contain the consequences.
Fox Run does not have one COD.
It has a series of completion tests that happen to converge in a good case and separate in a bad one.
The financing risk is in the separation.
Primary sources: SEC — Axial Basin Solar EPC Contract · SEC — SolarMax / Longfellow BESS EPC Transaction Disclosure · SEC — SolarMax 2025 Form 10-K / BESS EPC Status · SEC — Project Tax Equity / Completion Funding Conditions (2026)