How big are reactors, and has that changed?
The median operating reactor is 1,000 MW gross. Typical size rose for decades, from 50 MW in the 1950s to 1,188 MW in the 2020s. That median has not yet turned down, but 19 of today's operating units are 300 MW or under, the IAEA's line for an SMR.
The operating fleet by size
| Gross capacity | Units |
|---|---|
| Under 100 MW | 3 |
| 100-300 MW | 16 |
| 300-600 MW | 43 |
| 600-900 MW | 64 |
| 900-1,200 MW | 202 |
| 1,200-1,500 MW | 82 |
| 1,500 MW and over | 9 |
Median size by decade connected
Start year on record, for units now operating or retired. A decade with few units is a thin sample.
| Decade | Units | Median gross MW |
|---|---|---|
| 1950s | 17 | 50 |
| 1960s | 77 | 160 |
| 1970s | 159 | 784 |
| 1980s | 223 | 1,000 |
| 1990s | 44 | 1,013 |
| 2000s | 33 | 1,000 |
| 2010s | 61 | 1,086 |
| 2020s | 39 | 1,188 |
Sources
- Global Nuclear Power Tracker, Global Energy Monitor, August 2026 release , CC BY 4.0 · retrieved 2026-09-06
How these sources are used, including the corrections applied on top of them and what is deliberately left blank · download the underlying data
Cite this page
NuclearChain. "How big are reactors, and has that changed?." https://nuclearchain.net/capacity-distribution/. Accessed 2026. Built on the Global Nuclear Power Tracker, Global Energy Monitor, CC BY 4.0.
Free to reuse under CC BY 4.0 with that attribution. Download the data.