You’re out of free articles.
Log in
To continue reading, log in to your account.
Create a Free Account
To unlock more free articles, please create a free account.
Sign In or Create an Account.
By continuing, you agree to the Terms of Service and acknowledge our Privacy Policy
Welcome to Heatmap
Thank you for registering with Heatmap. Climate change is one of the greatest challenges of our lives, a force reshaping our economy, our politics, and our culture. We hope to be your trusted, friendly, and insightful guide to that transformation. Please enjoy your free articles. You can check your profile here .
subscribe to get Unlimited access
Offer for a Heatmap News Unlimited Access subscription; please note that your subscription will renew automatically unless you cancel prior to renewal. Cancellation takes effect at the end of your current billing period. We will let you know in advance of any price changes. Taxes may apply. Offer terms are subject to change.
Subscribe to get unlimited Access
Hey, you are out of free articles but you are only a few clicks away from full access. Subscribe below and take advantage of our introductory offer.
subscribe to get Unlimited access
Offer for a Heatmap News Unlimited Access subscription; please note that your subscription will renew automatically unless you cancel prior to renewal. Cancellation takes effect at the end of your current billing period. We will let you know in advance of any price changes. Taxes may apply. Offer terms are subject to change.
Create Your Account
Please Enter Your Password
Forgot your password?
Please enter the email address you use for your account so we can send you a link to reset your password:
Sweltering heat and earlier sunsets are a big problem for solar power.

The biggest problem in renewable energy goes by a few names.
Classically, it’s called the “duck curve,” which shows the relationship between solar generation and how much power the rest of the grid uses during the day. At the bottom of the curve, typically around midday, solar can sometimes generate 100% of the power demanded from the grid. But as the sun traces its arc towards the horizon, solar power generation falls and then quickly goes to zero as the sun sets. Often, temperatures and electricity use remains high, especially as people come home from work and start using home appliances, meaning non-solar sources of power must quickly come on line to fill in the gap.
It’s not a coincidence that utilities and grid operators tend to ask consumers to conserve in the later afternoon or evening. The phenomenon is classically associated with solar-heavy California, but it has come to Texas as well, where it goes by the name of the “Armadillo Curve” or the “Dead Armadillo Curve.”
But the relation between the sun and the Earth doesn’t just create darkness and light on daily scales but on annual ones as well. Yes, I know this isn’t breaking news, but it’s important, especially as the power system and climate are changing.
Right now we might be in the neck of the annual duck curve.
In case you haven’t noticed, the sun is setting earlier and it’s still really hot out. Kids are going back to school while much of the country is still facing summer temperatures.
In New York City this week, high temperatures are forecast to get into the 90s, while the sun will set before 7:30; in Washington, D.C., forecast highs are over 100 later this week with a sunset just past 7:30; in Houston, daytime highs to get over 100 later this week, with the sun setting before 7:40; and in Los Angeles , sunsets are at around 7:15 with expected daytime highs in the 90s this weekend.
And Septembers are only getting hotter. Septembers 2021 and 2022 were tied for the fifth hottest on record for the last 143 years, according to the National Oceanic and Atmospheric Administration; 10 of the hottest Septembers have occurred since 2012. The warmest was in 2020.
These higher temperatures mean prolonged periods of high electricity usage, even as one resource — solar — becomes less potent. This matters because, at least in the United States, we tend to organize our lives — and our electricity usage — around the clock, not the sun.
As the sun is setting earlier, our high electricity usage stretches longer compared to the length of the solar day, exacerbating the duck curve dynamics inherent to solar power. A dishwasher that runs when the sun’s still up in July is pulling the same power from the grid as one that runs during fall’s early twilight. The saving grace of shorter days in a grid that uses solar power is supposed to be that air conditioning usage goes down, but that doesn’t happen when summer temperatures persist past Labor Day.
If hot Septembers and even Octobers become the norm, grid conditions could tighten up both during and across the days, with higher cost, less reliable power or increased usage of fossil fuels to fill in the gap.
These longer, hotter summers can make operating electric grids more difficult. ERCOT, the electricity market that covers the vast majority of Texas, restricts power plants from having planned outages between May 15 and September 15 for maintenance. While still in the summer restriction window, ERCOT on Tuesday issued an alert for later this week, warning of “forecasted higher temperatures, higher electrical demand, and the potential for lower reserves.” If ERCOT extends its restrictions on outages for maintenance, there should be more unplanned outages, making power scarcer, meaning higher prices and a greater possibility of blackouts.
Not every country sees peak electricity usage in late summer. In New England, peak electricity demand tends to hit in July. In the sprawling PJM Interconnection last year, the electricity market that spans from the Chicago area to Virginia, demand peaks tended to be in June or August. In New York, peak demand is often in July.
But summer peaks are later in the year in two the country's largest electricity markets: California and Texas.
The Texas energy market had hit its peak day in July in 2022, but it moved out to August this year. And Texas is already bursting through its September demand records. It reached over 78,000 megawatts in just the first week of this month, well over its previous record of 72,370 megawatts, which it set in 2021.
And California hit its power demand record last September amidst a heat wave that covered much of the western United States.
It’s not just there being literally fewer hours of sunlight that drags down solar production later in the year, but also the lower angle of the sun. “As the sun gets lower in the sky we see solar production numbers will drop,” Joshua Rhodes, a senior research scientist at the University of Texas, told me.
“As the sun is lower in the sky it’s up fewer hours ... the photons are coming in at a steeper angle, the panels are not going to get as much light. Even when the sun is at the highest point of the day, the panels are not getting the same level of irradiance as when the sun is at the highest point of the day [at other times of year].”
The best angle for solar panels can change around 15 degrees a year, depending on the year and solar panels are more efficient when they can track the sun during the day. Most homeowners who install solar panels won’t have tracking technology, while utility-scale solar developers are more likely to. This means that a state like Texas, whose renewable mix is more focused on large solar arrays, could see less dramatic drop-offs in solar power throughout the day or throughout the year than a state like California, which has more residential solar.
A roof-mounted four kilowatt-hour solar PV system with standard specs where I grew up in Northern California would get 7.45 kilowatts-hours per meter squared per day in July, generating 689 kilowatt-hours of power, according to National Renewable Energy Laboratory PVWatts tool; in September, solar radiation would drop down to 6.6 kilowatt-hours per meter squared per day and 587 kilowatt-hours per month.
This admittedly basic math suggests it's possible California could struggle this month — and in future Septembers — with meeting electricity demand.
In the past 10 years, California’s annual load peak has occurred in September five times, with the peak loads in 2022 and 2021 occurring on September 6 and 8 respectively.
This year has been, so far, not particularly stressful for the Golden State’s grid thanks to some good luck — no region-wide, prolonged heat waves that max out California’s grid and make imports scarce, mild temperatures on the coasts where the state’s population is concentrated, no major wildfires, and plentiful hydro power thanks to massive snowfall this past winter — as well as massive deployment of batteries across the grid. The batteries especially can help alleviate these duck curve dynamics, as they essentially redistribute power from the sunniest part of the day to the evenings.
While Texas set several new records this year in electricity usage, California has stayed well short of its 52,000 megawatt record last September. California set records for solar power in June and July, with almost 16,000 megawatts, while total demand over 40,000 megawatts.
“While we haven’t seen substantial stress on the grid this summer, we haven’t been fully tested. If we got the kind of west-wide heat we experienced in September 2022, we could need to tap into the state’s emergency or strategic reserves again,” Anne Gonzales, a spokesperson for the California Independent System Operator, told me in an email.
Log in
To continue reading, log in to your account.
Create a Free Account
To unlock more free articles, please create a free account.
The former FERC chair explains why Chris Wright is likely to succeed where Rick Perry failed.
Neil Chatterjee thinks it’s going to go better this time.
Eight years ago, Chatterjee was the chairman of the Federal Energy Regulatory Commission, and Trump was the president. When Trump’s then-Secretary of Energy, Rick Perry, asked the commission to ensure that generators able to store fuel on site — which in the U.S. largely means coal and nuclear — get extra payments for doing so, thus keeping struggling power plants in business, it rejected the proposal by a unanimous vote.
“There’s no doubt my 2017 experience — that was politically driven,” Chatterjee told me, though he did concede that Perry was “right to be concerned about retiring generation at the time.” The Perry plan had been heavily influenced by the coal industry, he told me, and the regulatory structure of “compensating plants for having the attribute of on-site fuel … it was just a bit of a stretch.”
Now there’s a new Trump administration, with a new Secretary of Energy and a new FERC — and on Thursday, Energy Secretary Chris Wright asked the commission to do something else. He put forward what’s known as an advance notice of proposed rulemaking, directing FERC to come up with ways to help to make sure the grid can deal with another large-scale transition.
“They’re just apples and oranges,” Chatterjee said of the two requests. “This is a much more elegant, much more thoughtful exercise.”
Wright’s letter lays out the challenge of integrating large loads — i.e. data centers — onto the grid, arguing that they “must be able to connect to the transmission system in a timely, orderly, and non-discriminatory manner.” Doing so, he said, will “require unprecedented and extraordinary quantities of electricity and substantial investment in the Nation’s interstate transmission system.”
The overall thrust of the proposal is to make things easier and faster, including suggesting that interconnection studies for large loads that have their own generation or are flexible could be finished in just 60 days — which, if successful, could take a process that can last for years and get it done in less than a season.
The notice suggests a number of reforms for FERC to consider, including faster interconnection for “large loads that agree to be curtailable and hybrid facilities that agree to be curtailable and dispatchable” — touching on what has been the hottest subject in energy policy this year.
Tyler Norris, a Duke University researcher who has been one of the leading promoters of load flexibility, called Wright’s notice a “BFD” — that is, big effing deal — in a brief email to Heatmap.
Norris elaborated further on X. The proposal “appears to have done the near-impossible — generate overwhelming bipartisan enthusiasm — in what may be the most positive cross-sector response we’ve seen yet to DOE action under Secretary Wright,” he wrote.
Wright’s proposal suggests that both new data centers and new sources of power should be studied together for interconnection. While this sounds like it would be adding complexity, it may actually be simplifying the process. “Such an approach will allow for efficient siting of loads and generating facilities and thereby minimize the need for costly network upgrades,” the proposal says, reflecting the twinned desire to get more data centers on line faster while shielding electricity consumers from higher costs.
Another of Wright’s suggestions, however, might face more opposition. He argues that “load and hybrid facilities should be responsible for 100% of the network upgrades that they are assigned through the interconnection studies.”
This is designed to address the possibility — already being realized in parts of the country — that the network infrastructure required to bring data centers online could lead to higher costs for all electricity customers served by a given utility as it spreads out those costs to its rate base. The risk, however, is that utilities won’t like it. That’s because in most of the country, utilities earn a regulated rate of return on their investment in grid upgrades (by way of customer bill payments, of course), creating an incentive for them to continue to spend.
Those dynamics may be changing. Utilities once enjoyed primacy in Washington on electricity policy, especially among Republicans, but have seen their status slip of late in favor of a new force: big tech companies with big data centers.
“The hyperscalers have the influence to counteract the utilities here,” Chatterjee told me. “And that’s a new dynamic, historically — when it came to FERC, when it came to DOE, when it came to, quite frankly, Congress. People are sensitive to their utilities.”
Wright’s proposal, Chatterjee said, is trying to balance several different considerations the White House faces.
“This is the most vexing issue before the commission right now. And the reality is, it’s not clean politically within FERC, within DOE, even within the White House. There are differences of opinion on how best to thread this needle,” he told me, pointing to divides between those who want to drive AI development as fast as possible and those who are concerned about electricity prices.
By contrast, the Perry proposal to FERC was widely recognized as being primarily about supporting the coal (and to some extent nuclear) industry.
“I really think what DOE has put forward here is kind of an elegant solution that touches on everything,” Chatterjee said. “It’s not preferring particular sources of generation. It’s for flexibility — flexibility is having its moment.”
The proposal has already won some plaudits from the technology industry. In a letter to the White House, OpenAI Chief Global Affairs Officer Christopher Lehane wrote that the company “welcomed the news last week that DOE recommended to FERC that it assert jurisdiction and create standardized rules for large load interconnections.” He also noted that OpenAI’s data centers “are designed to be curtailable — reducing their draw or even returning power during peak demand, helping to protect reliability and avoid higher costs for consumers.”
The DOE gave FERC an April 2026 deadline for final action on the proposed rulemaking, and FERC said Monday night that comments would be due by November 14.
Chatterjee said he expects FERC to eventually issue rules based on the proposal on a unanimous and bipartisan basis.
“I think the initial thought was, Oh, here goes the Trump administration again, leaning on FERC. This is actually a thoughtful exercise that I think most people in the energy space recognize is necessary to be done.”
On global emissions, Bill Gates on Chinese nuclear, and a geothermal breakthrough
Current conditions: Hurricane Melissa made landfall over Jamaica as one of the strongest Category 5 storms on record before barreling north toward Cuba • A cold front will send temperatures plunging as far as 15 degrees below average across the mid-Atlantic and the Northeast • The Colombian Andes are bracing for flooding amid up to 8 inches of rain forecast for Wednesday.

The Trump administration’s all-of-government approach to thwarting construction of offshore wind turbines has included the Department of the Interior de-designating federal waters to turbine development and the Department of Transportation yanking funding, in addition to various steps taken by other agencies. Now the Department of Health and Human Services is taking its swing at the industry. On Tuesday, Bloomberg reported that Secretary of Health and Human Services Robert F. Kennedy, Jr. directed the Centers for Disease Control and Prevention to open an investigation into the potential harms offshore wind farms pose. In late summer, the agency instructed the CDC’s National Institute for Occupational Safety and Health to prepare research about wind farms’ impact on fishing businesses. The effort included Kennedy personally meeting with NIOSH director Josh Howard, in the course of which he gave Howard — a career physician and lawyer who previously oversaw federal efforts on September 11 victims’ health — specific experts to contact, according to the newswire report. The U.S. Surgeon General’s office has also been involved in the initiative.
It’s part of what Heatmap’s Jael Holzman called “Trump’s total war on wind,” an assault that started on President Donald Trump’s first day back in office. Earlier this month, oil major Shell’s top executive in the United States warned that the precedents the administration was setting risked being weaponized against fossil fuel companies once Trump exited power.
In the first real decline ever forecast by the United Nations, global emissions are now expected to fall by 10% below 1990 levels by 2035, according to a report issued Tuesday. But the world remains far off from the 60% reduction goal scientists say is necessary to keep warming below 1.5 degrees Celsius, the target leaders committed to when they signed the Paris Agreement a decade ago. “Humanity is now clearly bending the emissions curve downwards for the first time, although still not nearly fast enough,” Simon Stiell, executive secretary at the UN Framework Convention on Climate Change, told Bloomberg on Tuesday. “We have a serious need for more speed.”
The latest assessment comes as the U.S. is withdrawing from the Paris climate negotiations and other countries are paring back spending on decarbonization ahead of the UN climate talks in Belem, Brazil, next month.
On Tuesday, Bill Gates released a provocative new treatise on climate change in which he laid out what he sees as necessary ahead of November’s climate summit. Before that, on Friday afternoon, the billionaire philanthropist gathered with half a dozen journalists in a conference room in Manhattan to discuss his latest ideas over lunch. Heatmap’s Robinson Meyer, who was in attendance, has a good breakdown of some of what Gates discussed. I also attended the lunch and wanted to highlight another point Gates made: The West is losing the race for new nuclear power. When it comes to fission, China is building more reactors than anyone else, and helped perfect the Westinghouse AP1000 before its successful construction in the U.S. Gates’ own reactor developer, TerraPower, had plans to build its debut plant in China prior to the souring in relations between Washington and Beijing nearly a decade ago. When it comes to fusion, he said, there’s no topping how much funding China has directed toward the technology.
“The amount of money they’re putting into fusion is more than the rest of the world put together, times two,” Gates told us. “There is a substantial amount of Chinese capital going into that, and in fission, they built the most reactors.”
Chemical giant Honeywell has announced a new technology that converts agricultural and forestry waste into ready-to-use renewable fuels that can directly replace the carbon-intensive fuel used by large ships and airplanes. The so-called “Biocrude Upgrading” processing hardware can be provided in modular form and equipped to ships at a moment when global regulators are seeking to slash the roughly 3% of planet-heating emissions that come from cargo vessels. “The maritime industry has a real need for renewable fuels that are immediately available and cost effective,” Ken West, Honeywell’s energy and sustainability solutions president, said in a statement. The news comes nearly two weeks after Trump “torpedoed” — as Heatmap’s Katie Brigham put it — efforts at the International Maritime Organization to slash emissions from regulated ships.
The geothermal startup Eavor said Tuesday that its breakthroughs in drilling had slashed the time it takes to drill its wells underground. The Canadian company said that the results of two years of drilling at its flagship project in Geretsried, Germany, showed its efforts to dig to hotter and deeper locations are working. “Much like wind and solar have come down the cost curve, much like unconventional shale [oil and gas] have come down the cost curve, we now have a technical proof-point that we’ve done that in Europe,” Jeanine Vany, a cofounder and executive vice president of corporate affairs at Eavor, told Canary Media’s Maria Gallucci.
The breakup of the ancient supercontinent 1.5 billion years ago transformed the Earth’s surface environments and laid the groundwork for the emergence of complex life. That’s according to new research by Australian scientists at the University of Sydney and the University of Adelaide. The findings challenge what has long been called the “boring billion,” a time when biological and geological changes effectively stalled. The plate tectonics that reshaped the planet triggered conditions that supported oxygen-rich oceans and fostered the appearance of the first eukaryotes, the ancestors of all complex life. “Our work reveals that deep Earth processes, specifically the breakup of the ancient supercontinent Nuna, set off a chain of events that reduced volcanic carbon dioxide emissions and expanded the shallow marine habitats where early eukaryotes evolved,” Dietmar Müller, a University of Sydney professor and the study’s lead author, said in a press release.
Rob talks New Jersey past, present, and future with Employ America’s Skanda Amarnath.
Electricity prices are the biggest economic issue in the New Jersey governor’s race, which is perhaps next month’s most closely watched election. Mikie Sherrill, the Democratic candidate and frontrunner, has pledged to freeze power prices for state residents after getting elected. Can she do that?
On this week’s episode of Shift Key, Rob talks to Skanda Amarnath, the executive director of Employ America, a center-left think tank that aims to encourage a “full-employment, robust-growth economy.” He’s also a nearly lifelong NJ resident. They chat about how New Jersey got such expensive electricity, whether the nuclear construction boom is real, and what lessons nuclear companies should take from economic history.
Shift Key is hosted by Robinson Meyer, the founding executive editor of Heatmap, and Jesse Jenkins, a professor of energy systems engineering at Princeton University. Jesse is off this week.
Subscribe to “Shift Key” and find this episode on Apple Podcasts, Spotify, Amazon, YouTube, or wherever you get your podcasts.
You can also add the show’s RSS feed to your podcast app to follow us directly.
Here is an excerpt from our conversation:
Robinson Meyer: Is there a nuclear bubble? … As people who are interested in long-term decarbonization, number one, this is quite reminiscent of the environment that hit clean energy companies right as Biden was taking office. And number two, is there a nuclear bubble, and what does this mean for how we should think about nuclear going forward? Because at the end of this, I think the only way that any of this helps the climate is if we build a lot more plants.
Skanda Amarnath: We are definitely in a moment when there’s a lot of froth. I don’t want to say everything — it’s always like, it’ll feel unfair and not accurate to go after every single proposition that’s in markets. Like for example, Rick Perry’s Fermi America, they did an IPO and raised a lot of capital pretty successfully. And they have a plan for how they want to build a lot of stuff out — gas, solar, batteries. They want to build four AP1000s, the large, light-water reactors that are seen as the most recent that we’ve built in the United States, and they think they could do them at the same speed that China builds those same reactors.
On the surface of it, there are parts of it that seem interesting and promising. On the other hand, there’s also parts of it that feel very much wrapped up in the speculative frenzy. It gets more exaggerated when you get to like examples like Oklo. They seem to be very politically connected, specifically to Chris Wright. That plus some very small milestone successes in the fuel supply chain are now being sort of magnified into, They’re going be very successful in building out there first of a kind technology. And even in the space of small modular reactors, what they’re offering seems at least substantially more risky than what may be — outside of the space, so even compared to GE’s proposition for a small boiling water reactor, the technology that’s involved with like Oklo is kind of out there.
And one of the things, the lessons of nuclear, if you look through the history, is the more new stuff you’re doing, the harder it is, the more likely it is that you will get heartburn in terms of cost, in terms of schedule, and you never want to do this again. And it’ll involve a lot of bankruptcy, as it did with the case of the Georgia reactors that were built in the last decade. And so this is a sign that there’s clearly a lot of hype and a lot of willingness to take risk, and it’s not really backed up by fundamentals. That can be sometimes overrated in a boom. But that is something that people will look to in a bust and say, what were we doing here? Why was the price of the stock so high?
Mentioned:
How Electricity Got So Expensive
New Jersey’s Next Governor Probably Can’t Do Much About Electricity Prices, by Matt Zeitlin for Heatmap
Previously on Shift Key: The Last Computing-Driven Electricity Demand Boom That Wasn’t
Meta lays off 600 workers
Amazon lays off 14,000 workers
This episode of Shift Key is sponsored by …
Hydrostor is building the future of energy with Advanced Compressed Air Energy Storage. Delivering clean, reliable power with 500-megawatt facilities sited on 100 acres, Hydrostor’s energy storage projects are transforming the grid and creating thousands of American jobs. Learn more at hydrostor.ca.
A warmer world is here. Now what? Listen to Shocked, from the University of Chicago’s Institute for Climate and Sustainable Growth, and hear journalist Amy Harder and economist Michael Greenstone share new ways of thinking about climate change and cutting-edge solutions. Find it here.
Music for Shift Key is by Adam Kromelow.