Top 10 Countries Commissioning Nuclear Power Plants in 2025
This page compares where nuclear power projects are already in the construction-to-startup pathway. To keep cross-country comparisons clean, the ranking uses a single, consistently defined global database: IAEA PRIS.
The goal is not to predict who will finish “fastest”. It is to show where commissioning work is concentrated in 2025 as a pipeline signal: which countries have the largest number of reactor units beyond planning and in formal construction status.
Table of contents
What “commissioning” means here
In everyday speech, “commissioning a nuclear power plant” can mean anything from announcing a project to declaring commercial operation. In engineering practice, commissioning is narrower: it is the controlled transition from an installed system to a verified, operating system. For power reactors, that transition typically moves through staged handovers and tests before the unit becomes a steady grid asset.
A useful way to think about the commissioning path is as a sequence of verification steps that gradually increase system integration and operating complexity. The steps commonly include structured system turnover from construction to commissioning teams, cold functional testing (verifying systems without heat), hot functional testing (verifying systems under thermal conditions), low-power physics tests, first criticality where applicable, first synchronization to the grid, power ascension tests, and trial operation before a commercial date is declared.
Why PRIS matters for a global ranking: public communications often mix milestones and rely on planned dates that change. A comparable list needs a definition that is global and consistently applied. This page therefore uses PRIS reactor status “under construction” as the proxy for a country’s commissioning pipeline, because it is anchored to a defined start milestone and is maintained as projects move through status changes.
This pipeline lens is intentionally narrow. It measures how many units are already in formal construction status. It does not measure electricity generation, construction speed, total cost, or operational performance.
Indicator snapshot
Indicator: number of nuclear power reactors listed as under construction in IAEA PRIS, by country. The ranking also reports net electrical capacity under construction in MW(e), because a unit count alone can hide important scale differences. Two countries can have the same number of units while representing very different capacity additions.
Why this indicator works for 2025 comparisons: it is updated as a reactor’s formal status changes, and it is anchored to a construction start milestone rather than political announcements. For readers, it is also straightforward to interpret: a higher count generally implies more parallel project execution, more commissioning sequences to manage, and a deeper near- to medium-term addition pipeline.
Ranking rule: countries are ranked by reactor count. If countries tie on count, the tie-break is total net MW(e) under construction.
Method and calculations
The ranking is a PRIS snapshot that aggregates all reactors shown as under construction by country at the time of data capture. It is designed as a consistent “status-first” view, not a forecast model. A status-based ranking is less sensitive to narrative framing and avoids the common trap of comparing shifting planned dates across countries.
To keep the output transparent, the two share metrics are calculated directly from the PRIS global totals: share of global units is a country’s under-construction reactor count divided by the global count, and share of global MW(e) is a country’s total net MW(e) under construction divided by the global net MW(e) total.
Share formulas used in Table B:
share_units = reactors_country ÷ 63
share_mwe = mwe_country ÷ 66,297
A pipeline snapshot can change as projects enter construction, complete, or are reclassified in PRIS. If you update the page later, keep the same definitions and formulas so year-to-year comparisons remain meaningful.
Top 10 ranking tables
The ranking is split into multiple tables to keep typography readable and prevent overflow. Each table has no more than four columns.
Global baseline (PRIS): 63 reactors under construction worldwide, totaling 66,297 MW(e). Shares below are computed against these totals.
Table A — Pipeline size (units and MW)
| Rank | Country | Reactors | Net MW(e) |
|---|---|---|---|
| 1 | China | 29 | 30,954 |
| 2 | India | 6 | 4,768 |
| 3 | Russia | 5 | 5,000 |
| 4 | Türkiye | 4 | 4,456 |
| 5 | Egypt | 4 | 4,400 |
| 6 | United Kingdom | 2 | 3,260 |
| 7 | Korea, Republic of | 2 | 2,680 |
| 8 | Japan | 2 | 2,653 |
| 9 | Bangladesh | 2 | 2,160 |
| 10 | Ukraine | 2 | 2,070 |
Table B — Shares of the global pipeline
| Rank | Country | Share of global units | Share of global MW(e) |
|---|---|---|---|
| 1 | China | 46.0% | 46.7% |
| 2 | India | 9.5% | 7.2% |
| 3 | Russia | 7.9% | 7.5% |
| 4 | Türkiye | 6.3% | 6.7% |
| 5 | Egypt | 6.3% | 6.6% |
| 6 | United Kingdom | 3.2% | 4.9% |
| 7 | Korea, Republic of | 3.2% | 4.0% |
| 8 | Japan | 3.2% | 4.0% |
| 9 | Bangladesh | 3.2% | 3.3% |
| 10 | Ukraine | 3.2% | 3.1% |
How to read the list
A “Top 10 commissioning countries” list is easy to misread as a scoreboard of who will finish next. That is not what this indicator measures. “Under construction” confirms that a unit has crossed into formal execution and therefore belongs to the construction-to-startup pathway, but it does not guarantee a finish date. A country can rank highly because it is building many units in parallel, because it is building fewer but large units, or because it has clustered projects at one site. All three patterns create commissioning workload, but they imply different delivery profiles.
The two dimensions in the tables are separated on purpose. Unit count approximates how many parallel commissioning sequences must be planned: turnover packages, integrated tests, commissioning procedures, and grid coordination events. Net MW(e) approximates the scale of capacity represented by that workload. The United Kingdom is a good example of why both matter: its unit count is small, but its MW(e) share is larger than several peers with the same count, meaning the capacity represented per unit is high.
Finally, pipeline size should not be confused with system outcomes. Electricity supply and decarbonization impacts depend on what is already operating in the fleet, capacity factors, outage management, grid constraints, and demand patterns. This page stays narrow by design: it is a commissioning pipeline snapshot for 2025, built on one database and one rule, so comparisons remain consistent.
Country-by-country notes
The ranking is dominated by countries with sustained multi-unit construction programs. That matters because commissioning is not a single event; it is a repeating workflow. When several units move forward in parallel, industrial routines become more repeatable: test programs, training pipelines, and specialized contractors can be scheduled as a continuous stream rather than assembled from scratch for one unit. The PRIS count does not measure that operational maturity directly, but it often correlates with it: many active builds usually imply repeated commissioning sequences and a broader base of site and vendor activity.
The split between units and MW(e) helps avoid a common analytical mistake. Some countries have a small number of projects, but each project represents a large capacity block. Others build more units with smaller average unit sizes. The unit count is often a better proxy for parallel commissioning workload, while MW(e) is a better proxy for the scale of capacity additions represented by that workload. Reading both allows you to say not only “who is busiest”, but also “how much capacity is at stake”.
Practical use-case: use this section for the “pipeline map”, then consult unit-level PRIS pages when you need specific milestone dates such as first grid connection or commercial operation. The ranking is a snapshot; the unit pages are the audit trail.
China
China dominates the pipeline by both unit count and capacity. With 29 units under construction, it holds about 46% of global under-construction units and about 46.7% of global MW(e) under construction in this snapshot. That alignment between the unit share and MW(e) share tells you that the program’s scale is not only “many projects” but also “a large share of global capacity under execution”. In commissioning terms, this concentration usually implies a high cadence of late-stage testing and grid synchronization events over time, because parallel projects create overlapping commissioning windows.
India
India’s pipeline sits in the next tier by unit count. The interesting detail is the contrast between India and Russia: India shows 6 units and 4,768 MW(e), while Russia shows 5 units and 5,000 MW(e). In other words, the programs look similar by capacity, but India manages a slightly broader set of parallel commissioning sequences. This is exactly why keeping both lenses is useful: the “busy-ness” signal (count) and the “capacity block” signal (MW) are not always the same.
Russia
Russia’s MW(e) total is slightly higher than India’s despite fewer units, indicating a higher average unit capacity in the pipeline. For commissioning analysis, that can matter because larger units tend to have longer integrated test campaigns and more consequential grid integration planning. The PRIS snapshot should not be read as a schedule promise; it should be read as confirmation that these projects are in formal construction status and therefore carry real commissioning obligations rather than tentative plans.
Türkiye and Egypt
Türkiye and Egypt each show four units under construction, which is a meaningful concentration for countries scaling a nuclear program. Four units usually implies that commissioning processes cannot remain “one-off”. Site infrastructure, training, licensing work, and grid coordination must be organized across multiple units. In pipeline terms, that often marks a shift from a single-project build to a programmatic build where commissioning is planned as a repeated sequence rather than as an isolated milestone.
United Kingdom
The United Kingdom illustrates why MW(e) share should always be checked alongside unit count. With only two units in the pipeline, it still represents about 4.9% of global MW(e) under construction—higher than the MW(e) share of several other two-unit countries in the list. Put simply, the UK has fewer units but a heavier capacity footprint per unit. That difference changes how you interpret risk and impact: a delay or acceleration affects a larger capacity block.
Korea, Republic of and Japan
Korea and Japan both appear with two units under construction. In mature nuclear systems, a smaller construction pipeline can reflect policy cycles, a focus on operating performance, life-extension work, or timing effects where new builds are clustered in certain periods. A small pipeline does not equal low nuclear activity; it means fewer units are in the construction-to-startup pathway at the snapshot moment. If the question is “energy output”, you would pair this with operating-fleet metrics; if the question is “commissioning workload”, the under-construction status remains the relevant lens.
Bangladesh and Ukraine
Bangladesh and Ukraine close out the top 10 with two units each. Even at two units, the commissioning workload is substantial: integrated testing, readiness reviews, and the operational handover path require strong coordination. Where new-build is infrequent, institutional learning can be steeper, making standardized definitions and reporting even more important. PRIS provides that common status language and milestone definitions, which is why it is a useful backbone for a cross-country pipeline ranking.
These notes intentionally avoid plan-date narratives and focus on what the PRIS indicator supports: confirmed pipeline size, plus how to interpret count versus MW(e).
What changed in 2025
Pipeline depth and annual delivery are related but not identical. A country can have a large pipeline and still show only a small number of milestone events in a given calendar year, because late-stage testing can take time and milestones often cluster once integrated system readiness is achieved. PRIS tracks progress with milestone dates, most notably first grid connection and commercial operation, and it treats the period between those dates as trial operation.
To keep the 2025 picture concrete, the table below lists PRIS-highlighted first grid connections in 2025. This does not replace the ranking. It complements it by showing a “near-term movement” slice: which units reached grid synchronization during the year, independent of how large the longer pipeline is.
Table C — First grid connections in 2025 (PRIS highlights)
| Unit | Country | Net MW(e) | Date |
|---|---|---|---|
| Rajasthan 7 | India | 630 | 17 March 2025 |
| Zhangzhou 2 | China | 1,126 | 22 November 2025 |
Interpretation guardrail: first grid connection is not commercial operation. If you compare countries by “delivery in 2025”, keep the same milestone definition across the entire comparison set.
Visual comparison
The chart below scales each country to the top value (China, 29 units).
If you want a capacity-weighted intuition, compare net MW(e) in Table A and the MW(e) shares in Table B. Unit count emphasizes parallel commissioning sequences; MW(e) emphasizes the scale of capacity represented by those sequences.
FAQ
1) Why use “under construction” as the core ranking metric?
Because it is a defined status maintained in one global database and anchored to a construction start milestone rather than narrative announcements. That makes cross-country comparison more consistent than relying on plan dates that are frequently revised.
2) Is commissioning the same as commercial operation?
No. Commissioning covers the staged verification path from installed systems to operating status. PRIS distinguishes first grid connection from commercial operation and treats the period between them as trial operation, which is why milestone definitions must be kept consistent when comparing countries.
3) Why not rank only by units that entered commercial operation in 2025?
Annual completions can be sparse and sensitive to timing. A pipeline metric is more stable and answers a different question: where confirmed construction-to-startup work is concentrated, independent of which specific milestones happened to fall inside the calendar year.
4) Does a larger pipeline imply faster delivery?
Not necessarily. Delivery speed depends on execution, licensing, quality assurance, supply chain stability, workforce capacity, and site conditions. Use milestone dates (grid connection or commercial operation) for schedule analysis, and use the pipeline metric to describe breadth of active builds.
5) Why include net MW(e) as well as unit count?
Units vary in size. Net MW(e) describes the capacity available to the grid after internal plant consumption, making it a practical comparator. Two units can represent very different capacity blocks depending on unit size, so MW(e) prevents misleading “equal count” interpretations.
6) What exactly does PRIS mean by construction start?
PRIS defines construction start using a specific milestone commonly described as the first major placing of concrete for the reactor building base mat. That milestone is used to keep status reporting consistent across projects and countries.
7) Are small modular reactors included here?
The ranking includes whatever PRIS classifies as nuclear power reactors under construction at the time of the snapshot. Whether a project is marketed as an SMR is less important than its inclusion and status within PRIS for a consistent global comparison.
8) How should I verify one number for a specific country?
Use the PRIS country and unit pages to confirm current status and unit-level milestone dates. If you supplement with national regulator statements, keep the milestone definition consistent with PRIS (grid connection vs commercial operation) to avoid comparing different events.
Primary sources
The references below are used to extract the country totals, define status and milestone terms, and keep the indicator interpretation consistent. Each item includes a short note describing how it supports the page.
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IAEA PRIS — Under Construction Reactors by Country
Primary table for country totals and global totals used in Tables A and B.
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IAEA PRIS — World Statistics
Official PRIS statistics hub that explains global coverage and status categories.
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IAEA PRIS — Glossary
Definitions for construction start, first grid connection, commercial operation, and trial operation used for consistent terminology.
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IAEA PRIS — Home / Updates
PRIS update context and status-change highlights that help interpret snapshot timing.
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IAEA — Reference Data Series
Official IAEA statistical series that complements PRIS for reactor reference reporting conventions.
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IAEA — PRIS database description
IAEA description of PRIS as the reference database and its role as a reactor information source.
Method note: the ranking is intentionally status-based (PRIS) rather than plan-based. If you extend the page with time-to-milestone analysis, pull milestone dates from unit-level PRIS pages and keep milestone definitions consistent across countries.
Nuclear commissioning pipeline (2025) — tables and charts
Download the full assets pack used in this page: CSV tables, PNG chart images, and a machine-readable JSON dataset.
What’s inside
- tables/ — Table A, Table B, Table C in CSV format
- charts/ — PNG charts (units, net MW(e), unit share, MW(e) share)
- data.json — all tables in one JSON file
- README.txt — contents + calculation notes
