Published: November 9, 2025 | Updated: June 16, 2026
PROJECT EXECUTION
Japan’s “Preparation Zones” — junbi kuiki under the Offshore Renewable Energy Act — are the first formal step in the country’s three-stage designation ladder before an offshore wind area can be auctioned. As of June 2026, 17 areas carry this designation, and 11 of them (65%) are classified as floating wind sites. That concentration is not incidental. Fixed-bottom areas with favorable water depths have largely been absorbed into the higher-tier Promising and Promotion Zone categories; what remains in Preparation Zone status are predominantly deep-water sites where floating technology is a prerequisite and the technical and regulatory groundwork is more complex.
👉 Japan’s Offshore Wind Policy & Regulatory Framework — Legal Basis, Auctions, and Revenue Design
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Eleven of the 17 Preparation Zone areas require floating wind technology. Fixed-bottom areas with suitable water depths have progressively moved into Promising and Promotion Zone status, leaving the Preparation Zone tier as Japan’s deep-water floating wind inventory.
Oshima, Niijima, Kozushima, Miyake, and Hachijo are all floating-wind Preparation Zones. Each island has a small, isolated power system disconnected from the mainland grid, creating a structural mismatch between large-scale offshore wind economics and local demand scale.
Preparation Zone → Promising Zone → Promotion Zone is the pathway. Each step requires environmental assessment, fisheries consultation, and grid feasibility confirmation. Preparation Zone areas are not near-term auction candidates.
With floating CAPEX materially above fixed-bottom (JWPA baseline: approximately ¥908,000/kW for fixed-bottom offshore), advancing Preparation Zone areas into viable project pipelines depends on floating cost convergence over the 2030s.
Where Preparation Zones Fit in Japan’s Designation Ladder
The Offshore Renewable Energy Act — Saiene Kaiki Riyo Ho — structures Japan’s offshore wind development through a three-tier area classification system. Understanding where Preparation Zones sit in that ladder is essential for interpreting what the designation means and does not mean for developers and investors.
- Promotion Zones (Sokushin Kuiki): Areas fully designated for auction. Winners receive long-term ocean occupancy rights (30 years as a rule) and may proceed to construction. Twelve areas are currently designated. 👉 Promotion Zone Projects
- Promising Zones (Yūbō Kuiki): Areas that have advanced sufficiently through environmental studies, fisheries coordination, and grid assessment to be identified as Promotion Zone candidates. Nine areas are currently designated. 👉 Promising Zone Projects
- Preparation Zones (Junbi Kuiki): Areas at the earliest stage of the process — basic surveys under way, but not yet eligible for auction. This article covers the 17 currently designated areas.
Preparation Zone designation is a policy signal, not a development guarantee. It means the government has identified the area as a candidate for future offshore wind development and that baseline surveys have begun. It does not imply cost viability, grid access, fisheries clearance, or any timeline commitment. Advancement to a higher designation tier is determined through area-specific technical, regulatory, and economic assessment.
Preparation Zone status is not an occupancy permit, an auction announcement, or a project approval. The designation covers candidacy and survey initiation. Procurement pricing, grid constraints, and cost viability fall outside the scope of what designation determines — those are market conditions that each project must clear independently.
Preparation Zone Project Summaries
The following table lists all 17 areas currently designated as Preparation Zones under Japan’s Offshore Renewable Energy Act. Source: METI and MLIT publicly available records (as of June 2026). ※ Updated as new designations are made.
| Area | Technology | Details |
|---|---|---|
| Hokkaido Iwau / Minami-Shiribeshi Offshore (floating) | Floating | — |
| Hokkaido Shimamaki Offshore (floating) | Floating | — |
| Aomori Mutsu Bay | Fixed-bottom | — |
| Iwate Kuji Offshore (floating) | Floating | — |
| Chiba Asahi Offshore | Fixed-bottom | — |
| Tokyo Oshima Offshore (floating) | Floating | — |
| Tokyo Niijima Offshore (floating) | Floating | — |
| Tokyo Kozushima Offshore (floating) | Floating | — |
| Tokyo Miyake Offshore (floating) | Floating | — |
| Tokyo Hachijo Offshore (floating) | Floating | — |
| Toyama Eastern Offshore (floating) | Floating | — |
| Fukui Awara Offshore | Fixed-bottom | — |
| Wakayama Offshore (East) | Fixed-bottom | — |
| Wakayama Offshore (West, floating) | Floating | — |
| Saga Karatsu Offshore | Fixed-bottom | — |
| Nagasaki Goto South Offshore (floating) | Floating | — |
| Kagoshima Ichikikushikino Offshore | Fixed-bottom | — |
Breakdown: Floating — 11 areas (65%); Fixed-bottom — 6 areas (35%). Source: METI / MLIT public records, DeepWind analysis.
Why Floating Wind Dominates — The Deep-Water Structural Logic
The concentration of floating wind areas in the Preparation Zone tier reflects how Japan’s offshore wind designation process has worked. Fixed-bottom areas where water depth, seafloor conditions, and grid proximity support viable development have progressively been elevated into Promising and Promotion Zone status. What remains in the Preparation Zone is disproportionately composed of areas where floating technology is not optional — it is the only technically feasible approach.
The five Tokyo island areas illustrate this clearly. The Izu Island chain lies more than 100 km from the mainland grid. Each island operates an isolated small power system. Introducing large-scale floating offshore wind on these islands requires resolving a structural question that precedes project economics: whether the electricity is fed to the mainland via subsea cable, consumed locally, or some combination. Each scenario carries fundamentally different cost structures and grid investment requirements.
Nagasaki Goto South Offshore (floating) is geographically proximate to the existing 16.8 MW floating demonstration project at Goto — currently the only operational commercial-scale floating offshore wind project in Japan under the Promotion Zone framework. That geographic proximity creates a data-sharing and learning-transfer opportunity that could accelerate the advancement of the Goto South area through the designation ladder.
On cost, the gap matters: Japan’s fixed-bottom offshore wind CAPEX baseline is approximately ¥908,000/kW (JWPA, November 2025). Floating adds a significant premium above that level. For further detail on how this cost structure affects project viability, see: 👉 Offshore Wind Cost Structure and Economics in Japan
For the engineering basis of why platform type determines so much of the supply chain, see: 👉 Floating Offshore Wind in Japan: Market Structure, Costs, and Policy
Floating offshore wind faces a higher bankability bar than fixed-bottom: P90 energy yield uncertainty is greater where comparable deployment data is limited, and lenders require wider DSCR coverage to compensate. For Japan’s Preparation Zone floating areas, project finance conditions will remain challenging until the Goto demonstration and NEDO Phase 2 (2029 target) generate the operational data that allows lenders to model P90 yield with confidence. Under current lender risk appetite, achieving DSCR ≥1.35x for floating offshore wind in Japan remains difficult, placing most Preparation Zone floating areas outside near-term project finance scope.
Preparation Zones are strategic reservoirs for Japan’s floating wind pipeline — but the conditions for drawing on that reservoir are not yet in place.
The 17 Preparation Zone areas occupy the third tier of Japan’s offshore wind pipeline — behind Promotion Zones where FID (final investment decision) has not been reached, and behind Promising Zones where auction eligibility is the nearer-term question. In the current environment, where Promotion Zone FID failure is the dominant concern, a discussion of areas two steps further back may appear low-priority. That reading misses the structural logic.
The 65% floating composition of the Preparation Zone tier is not a characterization of difficulty — it is a characterization of where Japan’s future offshore wind capacity must come from. Fixed-bottom areas are finite. As they are absorbed into the promotion pipeline, the commercial pipeline for the 2030s and beyond is necessarily floating-dominated. Preparation Zones are the inventory that must supply that future.
The real question is the unlock sequence: floating CAPEX convergence and grid extension economics must both move before Preparation Zone areas can become real project pipelines. DeepWind’s focus is on whether NEDO Phase 2 demonstration data and platform standardization — through the semi-submersible pathway — can create financeable conditions for select Preparation Zone areas within the 2030s. The Tokyo island cluster remains a structurally distinct challenge requiring island energy system design before offshore wind economics can be evaluated independently.
Related DeepWind Articles
- Japan’s Offshore Wind Promotion Zone Projects — The Execution Structure Behind the Designations
- Japan’s Offshore Wind Promising Zone Projects — Next Auction Candidates
- Japan’s Offshore Wind Policy & Regulatory Framework
- Floating Offshore Wind in Japan: Market Structure, Costs, and Policy
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