Constellation Energy Corporation (NASDAQ: CEG) closed Thursday’s session (December 18, 2025) sharply higher and held steady in after-hours trading—capping a volatile stretch for one of the market’s most closely watched “AI power” and nuclear-linked names.
By the close, investors were weighing three fast-moving catalysts that can influence CEG at Friday’s open (December 19): (1) record-high PJM capacity auction prices tied to data-center demand, (2) a late-day Federal Energy Regulatory Commission (FERC) order directing PJM to create clearer rules for “colocated” AI/data-center connections, and (3) a meaningful procedural step in the antitrust review of Constellation’s planned acquisition of Calpine, including required divestitures. Reuters+2Reuters+2
Below is what happened after the bell, what the day’s biggest news means for Constellation Energy stock, and what traders typically focus on before the next market open.
CEG stock price check after the bell: where Constellation finished Thursday
Constellation Energy stock ended Dec. 18 at about $361.05, up roughly 5.9%, after trading in a wide range (roughly $346 to $371) on the day. Volume was about 3.77 million shares, near normal for a headline-driven utilities/independent power producer tape.
In after-hours trading, the stock was essentially unchanged around $361, with after-hours volume reported around ~125K shares shortly after 4:30 p.m. ET.
Why the “flat” after-hours matters: it suggests the market had largely digested the late news flow—particularly the FERC decision—without triggering another major repricing in extended trading. Friday’s premarket and first hour of cash trading will be the real test of conviction.
The biggest driver behind power stocks this week: PJM capacity prices hit the cap again
The dominant fundamental story for CEG right now is PJM Interconnection—the largest U.S. grid operator and the center of gravity for the Mid-Atlantic data-center power boom.
What PJM announced
PJM’s latest Base Residual Auction (for the 2027/2028 delivery year starting June 2027) cleared at $333.44/MW-day, the FERC-approved price cap, and again signaled a tightening supply-demand picture. Reuters reported the auction also fell short of PJM’s reliability requirement by roughly 6,600 MW, enough to power millions of homes.
PJM’s own release put the headline numbers this way:
- 134,479 MW of capacity procured
- $333.44/MW-day clearing price (cap)
- Total auction cost around $16.4 billion
- A shortfall of 6,623 MW relative to PJM’s target
- PJM also tied the demand jump to data centers, citing forecast peak load growth where ~5,100 MW of the increase is attributed to data-center demand
Why PJM’s auction matters so much to Constellation Energy
Constellation owns the largest nuclear fleet in the U.S., and a meaningful portion of its generation footprint participates in PJM markets. In Reuters-linked market commentary, Melius Research highlighted that CEG is among the more PJM-exposed large generators.
When PJM capacity prices rise, it can translate into higher forward capacity revenues for generators whose units clear the auction—especially for existing “always-on” resources (nuclear and gas) that the market leans on for reliability during tight conditions.
The pushback risk: political and consumer affordability pressure
The same auction that can be a revenue tailwind for producers is also drawing rising scrutiny because capacity prices are part of customer utility bills. Reuters notes some areas have already seen utility bill increases of more than 20% starting last summer and that governors have pushed for price controls.
What to watch before Friday’s open: any overnight follow-ups from state officials, consumer advocates, or utilities—because “windfall” narratives can spark calls for rule changes that ultimately affect PJM pricing, capacity market mechanics, or cost allocation.
Late Thursday headline: FERC directs PJM to write clearer rules for AI/data-center “colocation”
Thursday night brought a potentially market-moving regulatory update.
What FERC did (and why markets care)
Reuters reported that FERC directed PJM to establish rules governing the connection of AI-driven data centers and other large loads located next to power plants—an issue often described as “colocation” or “behind-the-meter” load. Reuters
Key takeaways from the Reuters report:
- Backers argue colocation improves efficiency and reduces the need for new transmission.
- Opponents warn it can reduce electricity available to the broader grid and raise bills.
- FERC said PJM’s tariff was “unjust and unreasonable” due to unclear terms and ordered revisions to detail conditions for serving colocated load. Reuters
The Associated Press framed the decision as a long-awaited order that could become a blueprint for how FERC handles these arrangements more broadly, noting the policy grew out of disputes tied to proposed colocation deals and concerns about cost shifting to regular ratepayers.
What it could mean for Constellation Energy stock
For CEG, the stakes are straightforward:
- If rules provide more certainty on how plants can serve colocated loads, it may support new data-center contracting models (especially for nuclear assets prized for carbon-free baseload).
- If rules evolve toward higher fees or stricter requirements to protect ratepayers, it could limit some economics of colocated deals—or slow the pace of implementation.
What to watch into Friday: investors will parse whether the market sees this as a net positive for incumbent generators (a “clarity + monetization” story) or as a sign of looming constraints (a “regulatory brakes” story). Reuters cited an advisory firm calling it a “major victory” for existing nuclear and gas plants because it directs PJM toward rules allowing power stations to reduce output to the grid to serve behind-the-meter customers. Reuters
Calpine acquisition update: DOJ settlement moves into a public-comment phase
Another notable “today” development wasn’t a flashy press release—it was a legal process milestone that matters for deal risk.
On December 18, 2025, the U.S. Department of Justice Antitrust Division published a Federal Register notice related to United States et al. v. Constellation Energy Corporation et al., tied to Constellation’s proposed acquisition of Calpine.
What the Federal Register notice says
The notice states that the U.S. filed a complaint alleging the Calpine acquisition would violate Section 7 of the Clayton Act, and that a proposed Final Judgment requires Constellation to divest specific Calpine generating facilities in:
ERCOT (Texas):
- Jack A. Fusco Energy Center (near Houston)
- Calpine’s minority ownership interest in Gregory Energy Center (near Corpus Christi)
PJM:
- Bethlehem Energy Center (Bethlehem, Pennsylvania)
- Edge Moor Energy Center (Wilmington, Delaware)
- Hay Road Energy Center (Wilmington, Delaware)
- York Energy Center (York 1 and York 2, near York, Pennsylvania)
It also notes public comment is invited within 60 days of the notice.
Why this matters for CEG before Friday’s open
Even if the market isn’t repricing the entire deal on this step alone, it’s a reminder that:
- The Calpine transaction remains a regulatory headline risk.
- Required divestitures can affect the eventual asset mix and synergy math.
- Timeline perception matters: procedural steps can shape investor expectations on when the deal can close.
What to watch: any commentary from antitrust specialists, utility analysts, or state officials reacting to the specific divestiture list—especially because it includes PJM plants, where the market is already hyper-focused on pricing and reliability.
Nuclear fleet headlines investors are still trading: license renewals and Three Mile Island restart messaging
Constellation is also getting “classic nuclear utility” news flow alongside the AI/data-center narrative.
NRC renewals: Clinton and Dresden (Illinois)
Constellation announced the NRC approved:
- a 20-year initial license renewal for Clinton, allowing operation through 2047
- a 20-year subsequent renewal for Dresden, allowing operation through 2049 and 2051
The company also said it is investing more than $370 million in upgrades tied to relicensing and noted that continued operation remains contingent on financial viability (with Clinton’s viability tied to a long-term agreement with Meta referenced in the release).
Three Mile Island / Crane Clean Energy Center: renewed political spotlight
A Pennsylvania public media report Thursday highlighted that U.S. Energy Secretary Chris Wright toured the site and that Constellation CEO Joe Dominguez said he expects the Crane Clean Energy Center (former Three Mile Island Unit 1) to be operational in summer 2027, describing PJM interconnection timing as a key hurdle.
Separately, DOE previously announced a $1 billion loan intended to help finance the restart of the 835 MW plant, framing it as support for reliability and AI-era power needs in PJM (subject to licensing approvals).
Why these nuclear updates matter for the stock: investors have been valuing CEG as both (a) a cash-flowing nuclear operator and (b) an AI-era power infrastructure play. Licensing and restart timelines directly affect perceptions of duration and growth runway.
What Wall Street is forecasting for CEG stock right now
For a snapshot of current sell-side sentiment, one widely cited compilation shows:
- Consensus rating: Buy
- Average price target: about $392.93 (roughly high-single-digit upside from the latest levels)
- Range: about $258 (low) to $478 (high)
This isn’t a “tomorrow morning” trading signal—but it’s a useful context check: the Street is still broadly constructive, while acknowledging a very wide range of outcomes (consistent with the regulatory and power-market uncertainty in the PJM story).
What to know before the stock market opens Friday, Dec. 19
Here are the most practical things to monitor overnight and into premarket if you’re following Constellation Energy stock:
1) Any fresh reactions to the FERC PJM colocation order
The Reuters and AP coverage frames this as a major national template issue for AI-era power access and cost allocation. Expect follow-up commentary from utilities, consumer groups, and grid experts.
2) PJM capacity auction “second-order” headlines
The auction price itself is known; what moves stocks next is interpretation: Who benefits most? Will politicians push back harder? Will PJM change market rules again? The shortfall and $16.4B cost figure keep this in the news cycle.
3) Deal-risk chatter around Calpine
The Federal Register posting is a reminder that divestitures are part of the pathway. Any sign that the market believes remedies are insufficient—or conversely, that they de-risk approval—can influence CEG’s next move.
4) The “quiet” after-hours action
CEG’s after-hours flatline near $361 suggests no immediate shock—but it also means Friday’s move could be driven by macro sentiment and early institutional positioning rather than a single late-breaking headline.
5) Key reference levels traders will talk about
Without turning this into a technical-analysis piece, note the obvious “tape levels” from Thursday:
- Thursday’s high near $371 and low near $346 define the immediate battleground.
- Earlier this week, a MarketWatch data note referenced CEG trading below a 52-week high of $412.70 (reached Oct. 15). That’s a psychological reference point for momentum investors.
Bottom line for Constellation Energy stock heading into Friday
Constellation Energy (CEG) goes into Friday’s session with momentum from a strong Thursday close—but also with policy and market-structure headlines that can cut both ways:
- Bull case near-term: PJM pricing tightness + regulatory clarity on colocation + ongoing nuclear fleet “duration” news keeps CEG positioned as a scarce large-scale clean baseload provider. Reuters+2Reuters+2
- Bear case near-term: the louder the “ratepayer pain” narrative gets, the higher the odds of political and regulatory interventions that could reshape PJM economics or slow certain data-center pathways. Reuters+1
- Deal watch: Calpine remains a live variable, with divestitures and process steps now in sharper focus.
