Fixed-bottom offshore wind in Japan costs about ¥908,000/kW to build, according to an industry survey of developers. That is roughly ¥410 billion for a 450 MW project, and installation alone takes a third of it. Official documents also carry figures as low as ¥388,000/kW, so the number you choose changes how a project looks.
Installation work totals ¥297,000/kW, more than the ¥270,000 spent on buying turbines. Foundations cost ¥86,000 to procure and ¥115,000 to install.
The higher figure includes contingency and onshore transmission, and it is a developer estimate rather than an audited cost. Match the scope before reading anything into the ratio.
Both use a 3% discount rate in a mechanical calculation. The industry body puts the required price in the mid-¥30s, and the government’s guide for new projects is about ¥30/kWh.
👉 Background: offshore wind cost structure
Where ¥908,000/kW goes: the cost breakdown by item
CAPEX is the money spent before a wind farm generates power. The Japan Wind Power Association (JWPA) surveyed developers of fixed-bottom projects in general sea areas, the waters tendered under Japan’s offshore wind law. It submitted the results to the government’s price-setting committee in January 2026. Eight developers responded, and the table shows the average for five projects using monopiles, the single large steel piles that support each turbine.
These are planned costs that can still change. JWPA is also an industry body, and this document asks the government to revise its ceiling prices, the maximum a bidder may offer in a tender. Read the numbers with that in mind.
| Item (¥10,000/kW) | Procurement | Installation | Total | Share |
|---|---|---|---|---|
| Turbines | 27.00 | 8.10 | 35.10 | 38.6% |
| Foundations | 8.60 | 11.53 | 20.13 | 22.2% |
| Subsea cables | 2.44 | 4.53 | 6.97 | 7.7% |
| Onshore transmission (30 km) | 2.87 | 4.67 | 7.54 | 8.3% |
| Substation | 1.76 | 0.86 | 2.62 | 2.9% |
| Survey and design | 2.54 | 2.54 | 2.8% | |
| Contingency | 7.23 | 7.23 | 8.0% | |
| Other | 8.70 | 8.70 | 9.6% | |
| Total | 42.67 | 29.69 | 90.82 | 100% |
Source: JWPA submissions, November 2025 and January 2026. Totals and shares calculated by DeepWind. The procurement and installation totals exclude survey, contingency and other costs. Other covers grid costs, insurance, construction interest, sea-area fees, staff and port fees.
Turbines are the largest single item at nearly 40%, once installation is included. Yet all installation work combined, at ¥297,000/kW, exceeds turbine procurement at ¥270,000. Foundations are the clearest case: installing them costs a third more than buying them.
Applied to JWPA’s reference project of 450 MW and thirty 15 MW turbines, the total is about ¥410 billion. That works out to about ¥13.6 billion per turbine position, a DeepWind calculation that spreads the foundations, cables and installation across each unit. It is not the price of a turbine.
How much site conditions move the figure
The ¥908,000 is an average. JWPA gives these rough sensitivities, and says their validity still needs separate checking.
- Water depth: going from 20.6 m to 26 m raises CAPEX to ¥973,000/kW.
- Seabed: monopiles in rock raise it to ¥1,335,000/kW, adding about ¥11/kWh to generation cost.
- Port distance and sea state: the base port moves from 22 km to 222 km away, with fewer workable days. Offshore turbine and foundation installation rises from ¥196,000 to ¥272,000/kW.
¥388,000, ¥565,000, ¥779,000 or ¥908,000: four CAPEX figures in public documents
Each of these appears in a public document, and each measures something different.
- ¥388,000/kW: the assumption behind the Round 3 ceiling price, with only ¥4,000 of grid connection. JWPA says it comes from the NEDO cost model, and that model assumes a European-style supply chain with no adjustment for Japan’s price gap.
- ¥565,000/kW: the benchmark in the committee’s September 2026 review of reported costs. It matches the construction cost assumed for feed-in tariffs from fiscal 2014 to 2019, plus grid connection.
- ¥779,000/kW: the average of four commercial projects in the periodic reports that subsidized generators file with the government, 38% above that benchmark. The document does not name the projects. Two demonstration units averaged ¥2,056,000.
- ¥908,000/kW: JWPA’s survey of planned costs for projects not yet built, including contingency and onshore transmission.
JWPA compares its survey with Round 3 line by line and arrives at 2.3 times overall. By item, turbines are 1.6, foundations 2.7, array cables 1.1 and installation 4.2. JWPA estimated the Round 3 split itself, and the scopes differ. Leaving out onshore installation brings that 4.2 down to about 3.5, by DeepWind’s calculation.
JWPA says inflation is part of the reason but gives no split by cause. In DeepWind’s view, a range from 1.1 to more than 4 times is hard to explain with prices alone. The gap in installation likely reflects the distance between a model built on European conditions and developers’ own plans for Japanese waters.
On international comparison, Japan’s price-setting committee assumes a 1.36 times gap between Japan and Europe for fixed-bottom projects. The actual gap depends on the date and scope compared, so no single ratio settles it. Our analysis of the auction outside the Sea Area Act looks at how far reported costs sit from past ceilings.
👉 Japan Offshore Wind Auction Outside the Sea Area Act
OPEX breakdown: ¥12,300 to ¥36,000/kW a year, depending on scope
OPEX is the cost of running the wind farm each year. The same word covers very different scopes in Japanese documents.
- ¥12,300/kW/year: JWPA’s survey average, covering only equipment maintenance and staff.
- ¥18,300: the same with insurance, about 1.4 times the Round 3 assumption of ¥13,200.
- ¥27,600: JWPA’s modelling figure, which adds port fees, sea-area fees, balancing costs and property tax.
- ¥36,000: the reported average of four commercial projects, 60% above the ¥22,500 assumption.
At ¥27,600 a year for 35 years, the undiscounted total reaches ¥966,000/kW, more than the original build cost (DeepWind’s simple sum).
IRENA, the International Renewable Energy Agency, puts the global weighted average at USD 100/kW/year. It splits that into turbine maintenance at about 60%, operational support 19%, insurance 11%, balance-of-plant maintenance 7% and other costs 3%. Treat that split as a global one. Floating wind has its own cost structure, covered separately.
👉 Floating Offshore Wind Cost Structure and LCOE Reality
Onshore transmission adds ¥75,000/kW, and distance pushes it higher
The line from the cable landing point to the grid connection averages 30 km in the survey and costs ¥75,400/kW. With contingency and onshore substations, JWPA puts the full onshore system at about ¥120,000/kW, or ¥3.4/kWh, and wants it added to ceiling-price calculations. Stretching the line to the survey’s maximum of 50 km adds another ¥1.6/kWh.
DNV expects the same pressure elsewhere. In Europe, fixed-bottom CAPEX falls toward 2060, but grid connection costs rise 14% as wind farms move farther out. Japan has now opened its exclusive economic zone to offshore wind, so more distant sites would likely push in the same direction.
LCOE of ¥21.1 and ¥22.4/kWh: similar numbers, different assumptions
Levelized cost of energy (LCOE) divides lifetime costs by lifetime output to give a cost per kWh, which lets different power sources be compared on one scale. The government and JWPA reach similar numbers today from very different inputs.
| Assumption | Gov. 2023 | Gov. 2040 | JWPA today |
|---|---|---|---|
| Construction (¥10,000/kW) | 51.5 | 32.5-33.7 | 90.8 (onshore system excluded from the LCOE) |
| O&M (¥10,000/kW/year) | 2.25 | 1.17-1.21 | 2.76 |
| Capacity factor | 30% | 40.2% | 36.6% |
| Operating life | 25 years | 25 years | 35 years |
| LCOE (¥/kWh) | 21.1 | 9.5-10.1 | about 22.4 |
Source: METI power generation cost review, draft summary (January 2025); JWPA submission (January 2026). All at a 3% discount rate. Government figures exclude policy costs.
JWPA’s construction cost is far higher, yet its LCOE nearly matches the government’s 2023 figure. One reason is a higher capacity factor, the share of maximum possible output a wind farm actually produces. The other is a 35-year life that relies on a 10-year extension of sea-area rights. The 36.6% comes from past ceiling-price settings, while the survey average is about 32%. JWPA estimates that using 32% adds ¥4.7/kWh.
The government’s ¥9.5-10.1 for 2040 starts from the ¥388,000 Round 3 assumption and lowers it 12-15% in line with International Energy Agency projections. That starting point is less than half of today’s survey, so the two cannot be read side by side. The report itself warns that its results are mechanical and do not match any price target.
Across sources, the 2023 figures are ¥10.0 for utility solar, ¥12.1 for onshore wind and ¥21.1 for fixed-bottom offshore wind. For 2040 they are ¥6.6-8.4, ¥10.1-11.6 and ¥9.5-10.1. None of these includes the system cost of balancing variable output.
The 3% discount rate is a common setting the government uses to compare all power sources, and it differs from a project’s cost of capital. IRENA assumes a real after-tax WACC of 7.30% for Japanese offshore wind in 2025. JWPA says a 6% project IRR needs a price in the mid-¥30s/kWh, including onshore and grid costs. The government’s guide for new projects is about ¥30/kWh. These measures are defined differently, so setting them side by side does not make them comparable. To test your own assumptions, use the DeepWind Simulator.
What it takes to reach ¥13.4/kWh by 2045
JWPA expects generation cost to reach about ¥13.4/kWh by 2045. That requires 30 GW of fixed-bottom projects by 2040, construction near ¥600,000/kW, 20 MW turbines at a 41% capacity factor and a 40-year life. It assumes costs fall 10% each time cumulative capacity doubles and that Rounds 2 and 3 reach operation on schedule. The figure excludes inflation.
Government targets point the same way. The first industry vision set 10 GW of projects by 2030 and 30-45 GW by 2040. The second, in 2025, added at least 15 GW of floating wind and a 65% domestic procurement share by 2040. Its summary also calls for an early review of the fixed-bottom cost target of ¥8-9/kWh by 2035.
For the differences between designated zones, see our comparison.
👉 Promotion zone LCOE and IRR comparison
In Japanese offshore wind, what a cost figure includes matters more than the figure itself.
The government’s ¥21.1 and ¥9.5-10.1 exist to compare power sources. Exercise caution if you are using them as a guide to revenue or project returns. For a project view, consider starting from JWPA’s line items and adjusting for water depth, seabed, port distance and onshore line length. Those are still planned costs, gathered by a body that is asking for higher ceiling prices.
Installation deserves the closest watch. It shows the widest gap, and it depends on base ports, vessels and workable days, so cheaper equipment alone will not fix it. As Rounds 2 and 3 move into construction, planned costs will start to become actual ones. Only then can anyone test which of the four CAPEX figures sits closest to reality. Until that happens, a range is a safer planning basis than any one number.
Related DeepWind Articles
- Offshore Wind Cost Structure and Economics
- Offshore Wind Disadvantages in Japan
- Japan Offshore Wind Auction Outside the Sea Area Act
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