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Fossil fuel plant retirements are slowing down, and projected load growth is to blame.

To fully decarbonize the electricity system will require more than just the rapid deployment of non-carbon-emitting generation capacity, plus the transmission necessary to get that electricity to where it needs to go. It will also require that our existing stock of electricity generation — which is largely natural gas- and coal-powered — get mostly mothballed. So far, this process has been proceeding briskly. Renewable deployment is on the way up and is projected to accelerate, and older electricity generation was sliding quickly but gracefully into retirement — until recently.
Retirements of existing generation have slowed down dramatically in the first half of this year, which is on pace to be the slowest for existing generation retirements since 2011, according to new data from the Energy Information Administration.
In the first half of the year, some 5.1 gigawatts of generating capacity have been retired, and another 2.4 gigawatts are scheduled to be retired by year’s end, for a projected total of 7.5 retired gigawatts. From 2004 to 2023, by contrast, just over 12 gigawatts of capacity were retired each year on average, with almost 15 gigawatts retired per year this decade. Since 2022, according to EIA data, over 90% of retired capacity has been coal or natural gas.
What’s behind the slowdown? “Reliability is threatened because the grid conditions are tightening,” Douglas Giuffre, executive director of gas, power and renewables analysis at S&P Global Commodity Insights, explained in an email. “This is partly due to the recent pace of coal and natural gas retirements in the U.S., which worked off some of the excess capacity in power markets. Now we are seeing tighter reserve margins, and a relatively thin pipeline of new gas-fired projects that can come online quickly.” That’s especially concerning for utilities at a time when projected electricity demand is way, way up.
The wave of retirements was a national phenomenon, often having nothing to do with state-level plans to decarbonize. Coal and gas were being retired so steadily over the past 20 years not just because plants were aging, but also because power use was essentially flat from the early 2000s through, essentially, yesterday. This meant that older plants — especially dirty coal plants — became uneconomic to run, especially as natural gas prices began to fall.
Now, we are in a completely different world. Electricity use is forecast to start growing again, thanks to a buildout of new data centers and manufacturing, plus the ongoing electrification of automobiles and home heating and cooling.
The Southeast offers an example of how these trends have played out on the ground. In December 2020, the Mississippi Public Service Commission determined that the state had “excess reserves … largely due to decreases in projected load” and ordered a 950 megawatt reduction in generating capacity by Mississippi Power by 2027. A consulting firm hired by the commission determined that Plant Daniel, a coal plant, was “relatively inefficient compared to other available resources;” a few months later, the utility said it would decommission Plant Daniel by 2027.
Then Georgia Power, the utility that covers most of the state (and, like Mississippi Power, a subsidiary of Southern Company), rushed out a new three-year plan for its future power usage less than a year after finalizing its old one. Its demand forecast through the end of the decade had jumped from 400 megawatts to 6,600 megawatts, the result of a projected boom in data center construction.
“They came in with a preselected list of ways it wanted to meet that power need,” including buying power from Plant Daniel and new gas, Bob Sherrier, a staff attorney at the Southern Environmental Law Center, told me. Georgia Power told the state’s utility commission that to respond to growing demand it would need to extend contracts with its sister utility in Mississippi — which meant not only that Daniel would remain open for at least another year — and build new new plants that could run on gas or diesel, plans for which regulators approved on Tuesday. The utility also hinted that its existing plans to euthanize, for the most part, its coal-fired generation fleet by the end of 2028 were likely to be revised.
“To meet that projected need, the utilities are reverting to what they know, which is fossil fuels,” Sherrier said.
In vertically integrated markets, where utilities own generating assets and sell power to customers, environmentalists have seen delayed retirements and the building of new fossil plants as examples of utilities slipping into their comfort zone, building and operating expensive projects instead of developing or procuring renewables to handle rising demand.
But it's not just in vertically integrated markets where fossil retirements are being delayed. In Maryland, for instance, Brandon Shores, a coal-fired power plant that was scheduled to close in 2025, is staying open because PJM Interconnection, the regional electricity market, determined that a plan to replace it with battery storage was not a “realistic option at present” nor “technically viable to resolve the reliability violations or avoid the need for an RMR agreement at this time,” PJM president Manu Asthana said in a letter to Paul Pinsky, the director of the Maryland Energy Administration. The transmission investments required to make up the difference, meanwhile, would take several years.
Along with the neighboring Wagner plant, which burns a mix of coal, oil, and natural gas, Brandon Shores will likely stay open more than three years past its planned retirement date thanks to what’s known as a “reliability must run” contract, which “would put Maryland ratepayers on the hook for over $600 million dollars in out-of-market payments,” according to a letter written by several Maryland congressional representatives to PJM.
Environmental advocates have blamed PJM for not doing enough proactive transmission planning to account for predictable and scheduled plant retirements.
The slowing retirements mean that emissions from the electricity sector, which have been falling since the mid-2000s (with occasional bumps up as the economy has recovered from downturns), are expected to plateau over the next year or so. EIA forecasts show carbon dioxide emissions from electricity as essentially flat from 2023 to 2025, with increased natural gas emissions essentially offsetting falling coal emissions.
There is a bright side to the data, however. So far this year, the U.S. has installed just over 20 gigawatts of new generation, 80% of which has been solar and battery storage, including a 600-plus megawatt projects in Nevada and Texas. If added generation comes on in the second half of this year as planned, the EIA projects we’ll have 15 gigawatts of battery storage by year’s end. Along with the large and growing solar generation in states like California, Nevada, and Texas, the U.S. is getting closer to a grid that can, at least, run without carbon emissions day or night.
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The spinoff of Lawrence Livermore National Lab has a new 10-point plan to get onto the grid by the 2030s.
One of fusion energy’s newest startups, Inertia Enterprises, is betting that the fastest route to commercial fusion runs through one of the field’s oldest ideas. The company, which raised a $450 million Series A earlier this year, plans to build a power plant based on the laser-driven fusion system pioneered at Lawrence Livermore National Laboratory’s — the only tech yet to have produced more energy from a fusion reaction than it took to initiate it. Now, Inertia has shared its commercialization roadmap exclusively with Heatmap, detailing the 10 near-term capabilities it must demonstrate before this landmark experiment can become a grid-scale power plant by the mid-2030s.
The roadmap offers a route from the national lab’s impressive but commercially impractical fusion demonstrations to an economical power plant capable of producing electricity for the grid. At its core are a set of milestones — mostly aimed at developing cheap, mass-manufacturable components — that Inertia says it must clear before those individual systems can be integrated into a working plant. This road is not necessarily linear, however, as various teams will likely be working on many of these goals simultaneously.
At least the physics of Inertia’s approach are already proven, the startup’s CEO Jeff Lawson told me, pointing to the fusion experiments at Lawrence Livermore’s National Ignition Facility as a proof-of-concept. The lab’s demonstration of net energy gain caps more than six decades and $30 billion (in 2026 dollars) of U.S. fusion research. The remaining challenges, he argued, are all engineering-related, requiring “elbow grease, hard work, and smart people” rather than breakthroughs in fusion science.
"It seems to us like a startup or a commercial company of any variety should be focused on commercializing a proven scientific result, as opposed to actually trying to demonstrate the basic science to begin with," Lawson told me. Basic science, he argues, is better left to national labs and universities, where researchers can pursue "unbounded problems" that don’t align with the expectations and timelines of venture-backed startups.
Indeed, no fusion startup has yet achieved scientific breakeven, the milestone Lawrence Livermore first hit in 2022, and has since repeated numerous times. But leading players such as Commonwealth Fusion Systems and Helion Energy maintain that it’s only a matter of time before they validate the physics behind their own reactor designs, which they claim will be highly cost-competitive.
Lawson, on the other hand, readily acknowledged that Lawrence Livermore’s tech is uneconomical in its current form. His bet is simply that the more predictable path to a commercial reactor is to drive down the cost of the lab’s validated fusion approach, known as inertial confinement. This system relies on high-powered lasers firing at a millimeter-scale pellet of fusion fuel, compressing it to extreme temperatures and pressures until the atoms fuse. Today, the National Ignition Facility makes each individual fusion target by hand, a workable solution given that it only uses about a dozen per year.
That production model, however, isn’t remotely plausible for a grid-scale power plant. Because each fusion reaction lasts just a fraction of a billionth of a second, a commercial facility must fire its lasers at a fresh target about 10 times per second to generate continuous electricity — requiring the production of hundreds of millions of targets each year.
Scaling production to roughly a million pellets per day and making them inexpensive enough for commercial operation without compromising the strength or precision required for fusion ignition is central to Inertia’s roadmap. That includes goals five, seven, eight and nine — industrializing the manufacturing of the carbon shells that hold the fusion fuel, making the thin films that hold those carbon shells both durable and cheap, scaling up and automating fusion target assembly, and speeding up how fast targets are filled with the requisite deuterium-tritium fuel.
The other central focus of the roadmap is the laser system, which will ultimately consist of 1,000 individual units operating in concert to compress and heat the fusion fuel. Key priorities include reducing the system’s cost (goal two), dramatically increasing its firing cadence (goal three), and bolstering its durability to withstand high-intensity operations (goal four). Goal six also complements these efforts, calling for the development of a control system capable of tracking moving fusion targets to precisely align each laser shot.
Goals one and 10 bookend the journey with some broader milestones. The first focuses on increasing the fusion target’s energy gain — the ratio of fusion energy produced to laser energy delivered — to more than 25 times ignition. Today, the National Ignition Facility’s best-performing laser shot has yielded a gain of just over four times what it took to start the reaction. Goal 10 then zooms out to the ultimate objective: integrating all these technologies into a commercially viable power plant that can deliver either electricity or industrial heat to end customers.
To reach that point, Inertia has embarked on an industrial engineering hiring spree, recruiting folks with experience taking complex hardware systems from prototype to mass production, “not unlike the processes that are used in the semiconductor or consumer electronics world,” Lawson explained. The company has been making progress on its component development goals since the beginning of the year, he told me, and expects to announce the successful demonstration of a few of these milestones in the coming months. Lawson ultimately expects Inertia to complete the core components of its laser and target manufacturing systems by the middle of next year.
The team will spend the next two to three years integrating these individual pieces into two fully operational subsystems, a prototype laser system and a target manufacturing line. Around 2030, the company will begin combining those subsystems into a first-of-a-kind fusion power plant, which will also serve as the proving ground for the target chamber, tritium fuel breeding system, and power conversion system that turns fusion heat into electricity. By the middle of the next decade, Inertia aims to be generating power from this first plant, setting the stage for the company to build and connect additional grid-scale commercial power plants.
There are plenty of engineering trade-offs that the company will have to solve for. Take the decision around how to size the target chamber, for example. “If you make it bigger, your walls have an easier time and survive longer, but it’s more expensive. If you make it smaller, your walls have a tougher time because they’re closer to all the heat and energy that the fusion reaction is creating, but now your power plant costs less to build.”
But to Lawson, this represents exactly the type of problem Inertia was built to solve: complex engineering issues that come to the fore once scientists have demonstrated the fundamental physics are sound. He thinks other fusion companies may someday reach this stage, as well — though he’s unwilling to hazard a guess on exactly what approach or startup is best positioned to do so.
“There have been generations of scientists who’ve made their predictions about fusion energy and gotten it wrong,” he told me. “I’m not going to pretend to be smarter than them. All I’m here to say is, just knowing that one did work, we can commercialize it.”