Free benchmark
Nuclear Availability Index
How much of the U.S. nuclear fleet is actually producing, as a single number. 100 means the fleet is running flat out; lower means more megawatts offline. Updated every morning, free to cite.
NukeGryd NAI · Sep 15, 2026
93.0
1-day +0.6
7-day -2.4
NAI, last 3 months
The availability index is a U.S. total and stays national: it cannot be re-cut per market by dropping units. The ISO-NE, PJM, Duke Progress, CAISO, BPA filter applies to the lists and boards on this page.
The seasonal dips are spring and fall refueling, when utilities take units down in the mild shoulder seasons.
Availability distribution
How many days the fleet ran at each availability level, 2026 to 2026 The fleet sits near 100 most days; the lower-availability bars are the spring and fall refueling seasons, when the biggest supply swings happen. An availability of 96 means 4% of nuclear capacity was offline that day.
Daily availability heatmap
Every day, colored by fleet availability, 2026 to 2026
Lower availability
Higher
No report
Each cell is one day. Refueling seasons show up as warm vertical bands every spring and fall. Hover a cell for the exact date and availability.
By ISO / region, today
lowest availability first| ISO / Region | NAI | MW offline | Nuclear capacity | Units |
|---|---|---|---|---|
| PJM | 94.1 | 1,939 | 32,692 | 31 |
| Duke Progress | 100.0 | 0 | 3,593 | 4 |
| BPA | 100.0 | 0 | 1,151 | 1 |
| CAISO | 100.0 | 0 | 2,240 | 2 |
| ISO-NE | 100.0 | 0 | 3,352 | 3 |
Methodology & citation
The NAI is U.S. nuclear generation divided by available nuclear capacity, expressed as a percent, summed over every operating unit reporting that day. It is the positive framing of "MW offline": an NAI of 96.0 means 4% of the fleet's capacity is offline for refueling, maintenance or a forced outage. Source data is the NRC Daily Power Reactor Status Report and EIA net-summer capacity, updated every morning. It is an availability measure, not a forecast.
Cite as: NukeGryd Nuclear Availability Index (NAI), 93.0 as of Sep 15, 2026. NukeGryd, NukeWorker.com.
Ontario (IESO) separate fleet
Ontario detailMW Offline
3,632 MW
29.9% of the Ontario fleet
Units Offline
4 of 16
Bruce, Darlington, Pickering
Delivering
8,528 MW
of 12,160 MW installed
Resolution
1 hour
vs. once-daily for the U.S. fleet
Ontario availability, tracked separately from the U.S. index. Ontario is reported as a separate fleet and is never added into the U.S. national figures above. IESO grid-operator market data (MW delivered), not NRC percent-power.