Market Briefing · updated daily

Markets

Where U.S. nuclear supply is tightest right now, and what is coming off line next. As of Sep 15, 2026 · Updated every morning from the NRC Daily Power Reactor Status Report.

Most-stressed Market

SPP

5.9% offline · 116 MW

MW in Refueling Now

1,227 MW

1 unit at a full outage

MW at Risk · Next 60 Days

megawatts due off line within 60 days

Biggest 30-day Mover

TVA

availability ▼ 15.0 pts

By Market

Available nuclear MW now, the day's move, vs 7-day and a year ago, and the 30-day trend, by balancing authority

ISO / RTO 13u

MISO

11,296 MW

98.1% available ↗ 183 MW DoD

vs 7d avg−14 MW (−0.1%)

vs 1 yr ago██

Fleet record ██ ██

Fall 26 avg offline 587 MW

What to watch Active: Clinton · −183 MW since Sep 12, 2026

Vertically Integrated 7u

TVA

6,953 MW

85.0% available 0 MW DoD

vs 7d avg−565 MW (−7.5%)

vs 1 yr ago██

Fleet record ██ ██

Fall 26 avg offline 183 MW

What to watch Active: Browns Ferry 1 · −1,227 MW since Sep 6, 2026

ISO / RTO 2u

SPP

1,832 MW

94.1% available 0 MW DoD

vs 7d avg−8 MW (−0.4%)

vs 1 yr ago██

Fleet record ██ ██

Fall 26 avg offline 38 MW

What to watch Active: Cooper · −116 MW since Aug 13, 2026

Available MW = nuclear generating MW now (installed nuclear MW minus what is offline), at the 98% full-power floor. DoD is the change since yesterday; the 30-day spark is the market's availability (% of its nuclear fleet generating). "What to watch" is the largest unit offline now, with the date it went down.

Biggest 30-Day Movers

Signed change in nuclear availability over the last 30 days

TVA

↘ −15.0 pp

SPP

↘ −3.9 pp

MISO

↗ +3.7 pp

Change in each market's nuclear availability (generating MW as a share of installed nuclear MW) between 30 days ago and today. Positive points = more nuclear back online.

Most-stressed Markets

By share of nuclear fleet offline, lowest availability first

Market	Type	Units	Availability	MW Offline	% Offline	Grid tomorrow	30d Δavail
TVA	Non-ISO	7	85.0%	1,228	15.0%	—	▼ 15.0
SPP	ISO/RTO	2	94.0%	116	5.9%	soft	▼ 3.9
MISO	ISO/RTO	13	98.1%	216	1.9%	soft	▲ 3.7

Availability = nuclear generating MW ÷ installed nuclear MW. "Grid tomorrow" is the day-ahead demand forecast vs the trailing-30-day norm, where a nuclear loss bites hardest. 30d Δavail is the change in the market's nuclear availability over the last 30 days.

Which market is about to be short, and by how much

Which units come off line next, when, and how much capacity is at risk by market (our sourced dates plus model projections) is part of NukeGryd Individual and up. Today's live market stress stays free.

See plans

Ontario (IESO) separate fleet

Ontario detail

MW 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 supply, for the northeast picture. 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.