Three Terms, Three-Layer Separation, Two Aprils —
Grid-Scale Battery Storage Contract Flow in Practice: 7 Failure Modes and 13 Checkpoints from the Field

In grid-scale battery storage (BESS) contract procedures, three terms — "Grid Connection Study" (接続検討), "Wheeling Service Contract" (接続供給契約), and "Generation Output Adjustment Supply Contract" (発電量調整供給契約) — are structurally prone to confusion. Carrying the procedural intuitions of the FIT-era solar PV world directly into grid-scale battery storage causes documents to bounce between recipients and premises to be misread. Project schedules shift by weeks or months as a result. The cause, in every case, is the same: the structural root of how these three terms were designed.

Behind that design lies a 66-character provision quietly embedded on April 1, 2024 into §8(2)(ho) of the wheeling tariffs of the 10 General Transmission and Distribution Utilities (TSOs) — §8(3)(ho) in Chubu Electric Power Grid alone.

Across the industry, hearsay circulates widely: "the rules changed in April 2026." Look at the tariff text, and the change isn't there. The reason is simple — the tariff hasn't moved. The real structural transformation had already happened two years earlier. These 66 characters rewrote the FIT-era and self-consumption-era assumption that "the Generator and the Generation Contract Holder are one and the same," replacing it with a three-layer separation: Generator ≠ Generation Contract Holder ≠ Trading Member. The legal foundation that makes aggregator-era contract flows possible was constructed right here.

The April 2026 tightening — 10% security deposits and a 50%-or-more initial installment requirement — is merely the first operational rule layered on top of that 2024 foundation. Without distinguishing which layer moved and which did not, the current state of the regulatory system cannot be grasped. This column unpacks the two Aprils structurally, breaks the three-term confusion into four layers, and reads — from primary sources — the seven failure modes observed in the field and the 13 checkpoints buyers should assemble in due diligence.

01 — The three terms in their proper places: statute, tariff, and form names live on different layers

Most confusion in grid-scale battery storage contract procedures stems from discussing three things on the same plane: the concept under the Electricity Business Act, the contract name in the wheeling tariff, and the application-form name used by each TSO. These are three different layers. They correspond, but not one-to-one. Without separating them first, every downstream discussion spins in place.

The table looks orderly at first glance. But in the field, multiple terms run in parallel and misreadings become routine. Three are particularly common. First, "Electricity Volume Adjustment Supply" (statute) and "Generation Output Adjustment Supply Contract" (tariff) are not separate concepts but stand in a containment relationship — upper concept and subordinate type (the tariff also has a parallel subordinate type, "Demand Suppression Volume Adjustment Supply Contract," for negawatts). Second, the word "Joint" (兼) in "Joint Application Form" is not a separate contract category, but a clerical convenience that merges forms. Third, "Grid Connection Study" (procedure) is not a contract at all — it is the pre-examination that precedes contracting, and the response letter carries a one-year validity period.

02 — The four structural roots of the confusion

The three-term confusion arises structurally from four layers. Each is independent, but they overlap to produce field-level confusion. Let me unpack them one at a time.

The four layers are independent yet interlock. Layer 1 is the containment structure of statute and tariff; Layer 2 is form merging; Layer 3 is the physical nature of batteries; Layer 4 is the agency-power provision created in April 2024. The three-term confusion is the product not of a single cause but of all four layers tangling together at once. That is why surface-level terminology cleanup alone never quite resolves it.

03 — The 66 characters of April 2024: the day the structural foundation was built

Why does Layer 4 deserve to be called "the structural transformation of April 2024"? To show this with structural facts, I need to put the old tariff and the new tariff side by side.

Before March 31, 2024, the wheeling tariffs did not even contain the contract category "Grid Connection Reception Contract" (系統連系受電契約). The tariffs were built on the unspoken assumption that Generator and Generation Contract Holder were the same entity. The new tariff effective April 1, 2024 newly created the "Grid Connection Reception Contract" for the first time. The reason was practical: with the introduction of the generation-side wheeling charge (the Grid Connection Reception Service Fee), the direct fee relationship paid by generators to the TSO had to be legally structured. Alongside this new contract category, a provision was simultaneously introduced — uniformly across the 10 TSOs — empowering the Generation Contract Holder to conclude that contract on behalf of the TSO. Not a partial amendment — a complete new creation.

3-1 Uniform across all 10 TSOs — 66 characters embedded in near-identical wording

The exact wording of the newly created provision is the 66 characters quoted at the head of this column. It is embedded in near-identical form into §8(2)(ho) of the 10 TSOs' wheeling tariffs (§8(3)(ho) in Chubu Electric Power Grid alone). Including Okinawa Electric Power — which has not implemented legal unbundling — the wording is aligned nationwide. (Punctuation style — commas — may differ slightly across utilities.) The press release issued by Chugoku Electric Power Transmission & Distribution on January 17, 2024 captures the essence of the new scheme most plainly: "Tariff collection shall be performed by the Generation Contract Holder on behalf of the Company; the Generation Contract Holder shall, as a general matter, remit payment to the Company by utilizing the framework of the Generation Output Adjustment Supply Contract." Nine months after the effective date, in January 2025, the secretariat of the Electricity and Gas Market Surveillance Commission released "Reference Materials for Generators on the Generation-Side Charge," stating in writing: "At the formation of the contract, the Generation Contract Holder responds as agent for the General Transmission and Distribution Utility."

It is worth noting that even Okinawa Electric — which has not undergone legal unbundling — follows the same chapter structure (Chapter II), the same section number (§8), and the same wording. Regardless of whether legal unbundling has been completed, the agency-power provision was incorporated at the tariff level nationwide. This was not "the independent response of a few utilities" but a cross-industry standard model change.

3-2 The new scheme has two stages

This two-stage structure is what makes the aggregator-intermediated scheme legally feasible. Once an aggregator (a Specified Wholesale Supplier) takes the position of "Generation Contract Holder," it automatically holds the position of agent-for-contract-conclusion under Stage 1, and additionally functions as agent-for-fee-collection under Stage 2. The Generator performs only the physical generation (operation of the battery), while contract administration and the entire fee flow are handled between the Generation Contract Holder and the TSO — this structure was made possible at the tariff level for the first time in April 2024.

04 — The three-layer separation of the aggregator era: Generator, Generation Contract Holder, Trading Member

Against the backdrop of §8(2)(ho) of April 2024, the contractual parties around a single grid-scale battery can separate into three layers.

These three may all be the same entity, or all different. EPRX (the Japan Electric Power Reserve and Adjustment Exchange, distinct from JEPX), in its published "Guide on Participating in the Balancing Market Using Pumped Storage or Battery Storage Facilities" (Edition 2, dated April 1, 2025), states the point explicitly: "The party concluding the Generation Balancing Contract and the Trading Member do not need to be the same entity." The same logic applies to the charging side.

What this means in practice: the BESS owner (Generator) may itself contract directly with the TSO as Generation Contract Holder, or it may have a Specified Wholesale Supplier (an aggregator) step in as Generation Contract Holder in its place. The trading member, in turn, may be yet another aggregator. Ownership, contracting, and trading are designed so that all three layers can be separated.

Once the three-layer separation is understood, a common field remark becomes legible: "We'll submit the main application once the aggregator's documents come together next week." When an aggregator steps in as Generation Contract Holder, the Joint Generation Output Adjustment Supply and Basic Contract Application cannot be submitted to the TSO until the aggregator's corporate information, market participation setup, and supply-demand plan submission setup are all in place. The project is not one the owner can drive alone, so the sequencing is keyed to the aggregator.

4-1 "You can't proceed until you decide the retailer" is an explicit tariff requirement at all 10 TSOs

The flip side of the three-layer separation is a requirement repeatedly raised in the field by TSOs: "The Wheeling Service Contract application cannot proceed until the Retail Electricity Provider is decided." This is often treated as an operational convention, but in fact it is an express requirement in the wheeling tariffs of all 10 TSOs.

Two streams of provisions form the core. First, the definition of "contracting party" itself is limited — in the tariffs of Chubu PG, Kansai Transmission & Distribution, Hokuriku Transmission & Distribution and others — to a party "supplying electricity to the contracting party for use in the contracting party's retail electricity business, specified transmission and distribution business, or supply to itself." Second, as an attachment requirement for the consumer consent document, §8(1)(he) and §9 of the tariffs of Hokkaido NW, Tohoku NW, TEPCO PG and others expressly require: "a copy of the consumer's consent to the contracting party… shall be submitted together [with the application]."

In other words, this requirement is not TSO operational discretion or case-by-case judgment — it is the architecture of the tariff itself. Unless the BESS owner either obtains a retail electricity license itself or fixes a specified Retail Electricity Provider as the contracting party, the Wheeling Service Contract application cannot proceed by the structure of the tariff. The hope that "the TSO will be flexible here" misses the mark.

4-2 The "via-retailer flow" does not fall within the tariff's use requirements

Another typical misunderstanding is the framing: "the Wheeling Service Contract goes via the retailer, while the Generation Output Adjustment Supply Contract goes directly to the TSO." In reality, for grid-scale battery storage, both filings on the generation side are made directly to the TSO as standard.

The most lucid answer comes from materials published by the Agency for Natural Resources and Energy's Working Group on System Design in Light of the Verification of Electricity System Reform (7th meeting), dated November 28, 2025: "Under the General Transmission and Distribution Utilities' Wheeling Supply Tariffs, Retail Electricity Providers and similar entities may use the grid only when conducting retail supply." "Of the electricity supplied to battery storage operators, the portion other than the 'storage and similar losses'… is not the subject of wheeling supply conducted by the General Transmission and Distribution Utilities, and is understood not to permit grid use." The very act of a Retail Electricity Provider using the grid on behalf of a battery is structurally not contemplated under the tariff. The "via-retailer flow" is not so much prohibited as it simply does not satisfy the tariff's use requirements — and therefore cannot exist.

05 — April 2026: setting a regulatory zero point with no transitional measures

If the agency-power provision of April 2024 was "the foundation of the aggregator era," then the first operational rule layered on top of it is the BESS-only tightening of April 1, 2026. Following the consolidation work at METI's Next-Generation Power Grid WG sessions (6th meeting on December 24, 2025; 7th meeting on February 9, 2026), OCCTO published a nationwide uniform rule revision on March 18, 2026, which was then implemented in each TSO area.

5-1 The boundary line is the "contract application receipt date" — and that alone

Editorially, the most important feature of this measure is that no across-the-board transitional measure was set. As TEPCO Power Grid expressly stated in its April 1, 2026 notice, the boundary condition is, in principle, the single point of "whether the contract application was received on or after April 1, 2026."

In other words, a project that has already received its Grid Connection Study response within 2025 and is about to proceed to contract application is fully in scope of the new rules (10% deposit; 50%+ initial installment) if the contract application is received on or after April 1, 2026. There are, however, narrow carve-outs by category: (i) the congestion-mitigation process remains at 5% and is out of scope; (ii) for batteries co-located with generation or demand, the project is in scope only when "the principal facility" is judged to be the battery based on facility capacity (the judgment is made by each area's TSO/distribution utility); (iii) where installment payment is genuinely difficult, the TSO retains room for an exception with stated reasons. These are individual judgment frameworks — not a "transitional measure" that uniformly excludes a category of projects on a time axis. The expectation "we cleared the Grid Connection Study last year so we can proceed under the old rules" does not survive under this measure. This column calls this design "setting a regulatory zero point with no transitional measures." Read another way, it is a deliberate design choice that refuses to leave the question of retroactivity ambiguous — in order to suppress speculative Grid Connection Study filings.

5-2 OCCTO as the rule-making body

The other striking point is that this tightening was implemented not as a series of independent responses by each utility, but as a nationwide uniform measure led by OCCTO. OCCTO revised the "Security Deposit Calculation Methodology" and "Approach to Construction Cost Contribution Payment Term Changes"; each General Transmission and Distribution Utility then issued individual notices to follow. The agency-power provision of April 2024 was implemented as a wheeling tariff amendment under EBA Art. 18(1) (requiring ministerial approval from METI), whereas the April 2026 tightening was implemented as a revision of OCCTO's business rules and Transmission and Distribution Business Guidelines under the Art. 28-41 family, together with accompanying published materials (ministerial approval is still required for business rule and guideline revisions, but the route and the principal body differ). The industry's locus of rule-making has shifted — from the tariff-approval route to the OCCTO wide-area-rule revision route. This is a key observation point for reading the future direction of contract flow regulation.

06 — Nine phases and the "who submits what to whom" matrix

With the three terms and the three-layer separation now organized, the contract flow can be laid out chronologically. From a Grid Connection Study application to commercial operation date (COD), a grid-scale battery passes through nine phases.

6-1 "Who submits what, and to whom" at each phase

Across the nine phases, the submitting party and the recipient change frequently. Mistakes here leave documents in mid-air. The matrix below reflects the three-layer separation (Generator, Generation Contract Holder, Trading Member).

What the matrix makes visible is that the submitting party switches frequently — Retailer (E-3) → Generation Contract Holder (E-4) → Generator (E-5, E-6) → Trading Member (E-9). When these layers are different legal entities, the entire phase stalls whenever inter-party coordination breaks down. An owner can drive all nine phases alone only if it has itself acquired a retail electricity license, registered as Generation Contract Holder, and obtained trading membership in its own name. In aggregator-intermediated projects, the rate-limiting step shifts every time the responsible party changes.

6-2 Pre-Use Self-Confirmation and TSO documents are on separate tracks

What must not be missed at E-6 is the relationship between the Pre-Use Self-Confirmation Result Notification and the documents issued by the TSO. The former is a public-law safety regulatory filing submitted by the installer (i.e., the Generation Contract Holder) to the Competent Minister (Director-General of the Industrial Safety Inspection Department) under EBA Art. 51-2(3) and Enforcement Regulation Art. 78 (Form No. 53). The latter is a private-law contractual document evidencing contract formation and start-of-interconnection. The two run on independent tracks. Operationally, the sequence is:

Acceptance of the Pre-Use Self-Confirmation Result Notification is what satisfies the legal "commencement of use" requirement. The TSO-issued document (or email notice) is what satisfies the contractual COD requirement. If the two are conflated, the date of operation start can diverge between law and contract. In buyer-side due diligence, the rule of thumb is to assemble both — as two separate tracks.

07 — There is no "interconnection completion notice": the transparency shadow

One issue regularly shakes buyer-side due diligence in BESS transactions. No stand-alone standard form titled "Receiving Test Pass Certificate" or "Interconnection Completion Notice" exists — neither in OCCTO's Transmission and Distribution Business Guidelines, nor in the 10 TSOs' wheeling tariffs, application flows, or FAQs. Within this column's research scope — a sweep of the 10 TSOs' public web pages — only four standard forms could be confirmed: (i) the Grid Connection Study Response, (ii) the Interconnection Approval / Contract Application Response, (iii) construction cost contribution documents, and (iv) the Pre-Use Self-Confirmation Result Notification (addressed to METI, prepared by the installer).

So in practice, what fixes the start-of-interconnection date? Each utility handles it through documents or email notices.

To consolidate: no standard document attests to "passing the receiving test" on a stand-alone basis. In practice it is absorbed into contract execution notices and start-of-interconnection notices, and at some utilities — notably TEPCO PG — it is delivered as an email rather than a paper document. Several utilities publish forms or samples. Two points deserve special attention: Shikoku Electric Power Transmission & Distribution publishes a sample PDF of "Notice on Contracts Concerning Grid Interconnection," and Tohoku Electric Power Network's "Concerning the Commencement of Grid Interconnection" is a notification from the Generator to the TSO (to be submitted at least one week before the planned start date) — not a completion notice from TSO to Generator. When buyer-side due diligence asks "what evidence do you have of interconnection completion?", in many cases there is no physical document — only an email from the TSO to the Generator. That is precisely what shakes buyers' footing in DD.

08 — Seven failure modes observed in the field

With the three-term confusion, the misreading of the three-layer separation, and the two-April boundary all in view, the failure modes observed in the market come into focus. The seven enumerated below are patterns generalized from cases that have actually occurred in the field. None of them show up in the standard project financial model, but each directly shakes project schedule and cash flow.

What unifies all seven is that they arise from carrying FIT-era solar procedural intuitions into the battery world. Each is the kind of failure that can be avoided in advance, simply by working through the three-term confusion structurally. The order — "tidy up first, then go into the field" rather than "stumble first, then tidy up" — is what stabilizes project schedules and cash flows.

09 — M&A DD: 13-point checklist

In buyer-side due diligence, the document sets expected at each phase become standardized. The 13 items below are the lowest common denominator of the document list a buyer should request from the seller.

※ Check results persist only within the browser session. Whether the 13 items are complete — or not — visualizes the project's progress depth and the buyer's risk perception. For unchecked items, proceed on the basis that the seller should explain what each missing item means (unpaid deposit / undetermined aggregator / unconfirmed construction cost contribution, etc.).

10 — "How to move from today" for five reader profiles

Even after the three-term confusion, the two Aprils, and the three-layer separation have been organized, the column does not help in the field unless each reader can translate the analysis into action from their own position. This chapter sets out, by reader profile, what to do starting tomorrow.

11 — Track the layer that is moving: regulatory monitoring points

Holding the April 2024 agency-power provision and the April 2026 tightening side by side reveals that the industry's locus of rule-making has shifted. April 2024 was implemented via a wheeling tariff amendment passing through METI's approval (EBA Art. 18(1)); the April 2026 tightening was implemented as a revision of OCCTO's wide-area rules (ministerial approval is still required for business rule and guideline revisions, but the route and principal body differ). To read the operational rules that will continue to accumulate going forward, the reader must look in the right place.

Hearsay that "something big changed in April 2026" is widely circulated, but at the level of wheeling tariffs, statutes, and the grid interconnection technical guidelines, it is a factual error. What moved was the OCCTO business rules and balancing market regime — "OCCTO wide-area rules and the markets," not "the tariffs." Checking the tariff text yields no change. The movement is happening on a different layer. For this column's readers, the place to track the latest regulatory movement is not the wheeling tariff but METI Next-Generation Power Grid WG materials and the operational manuals of the balancing and capacity markets.

Conclusion — The three-term cleanup, the two Aprils, and the field instinct for avoiding failure modes

What I wanted to convey through this column reduces to three points.

First, what rewrote the grid-scale battery storage contract flow was not April 2026, but April 2024. The 66 characters embedded in near-identical wording into §8(2)(ho) of the 10 TSOs' tariffs (§8(3)(ho) in Chubu PG alone) established at the tariff level the three-layer separation "Generator ≠ Generation Contract Holder ≠ Trading Member," constructing the structural foundation of the aggregator era. The April 2026 tightening (10% deposit; 50% initial installment) is merely the first operational rule layered on top of that foundation. Without distinguishing which layer moved and which did not, the current state of the regulatory system cannot be grasped.

Second, the three-term confusion can be resolved structurally. "Electricity Volume Adjustment Supply" and "Generation Output Adjustment Supply" are not divergent — they stand in a containment relationship. "Wheeling Service Contract" and "Generation Output Adjustment Supply Contract" are not the same thing — they are two parallel tracks. The "via-retailer flow" does not satisfy the tariff's use requirements and therefore cannot exist. The three-layer separation (Generator, Generation Contract Holder, Trading Member) is legally organized through the combination of the Specified Wholesale Supplier regime (effective April 2022; source: Act No. 49 of 2020) and the §8(2)(ho) agency-power scheme (effective April 2024).

Third, failure modes can be avoided in advance. All seven failure modes enumerated above arise from carrying FIT-era solar procedural intuitions into batteries. Once the three terms are sorted out, the meaning of the three-layer separation is understood, and the two-April boundary is internalized, all seven are avoidable. The order — "tidy up first, then go into the field" rather than "stumble first, then tidy up" — is what stabilizes project schedules and cash flows materially.

The grid-scale battery storage contract flow is too complex to be read through the FIT-era solar vocabulary. But complexity that has structure becomes a basis for judgment once decoded. Without amending the Electricity Business Act, the aggregator-era contract flow has been assembled out of tariff and operational guidance — this is the editorial message of this column. To read the operational rules that will continue to accumulate, the starting point must be the tariff-level foundation that sits beneath them — the single phrase, "the Generation Contract Holder, acting as agent for the Company."

Investment decisions in grid-scale battery storage are decided by the capacity to read the structure embedded in the tariff. If this column serves as one foothold for that reading — and for avoiding stumbles in the field — its purpose is fulfilled.