The US cuts the mileage new cars must average in 2031 from 50.4 to about 35 miles a gallon, and missing it already costs carmakers nothing

The stories

12 on this beat today.

Every story told the same way: what happened, who is involved, why it matters, how it works, the truth and the good news.

1. 01

   The US cuts the mileage new cars must average in 2031 from 50.4 to about 35 miles a gallon, and missing it already costs carmakers nothing

   50.4 to about 35

   miles a gallon a carmaker's new 2031 vehicles must average, before and after Monday

   the sources give the new figure as 34.5 and 34.9 [1][2]

   $0

   fine for a carmaker whose vehicles miss the standard

   the US Congress cut it before Monday's rule [1][2]

   $185bn

   more spent on fuel, by NHTSA's own estimate

   Electrek reported it with a rise of about 5% in carbon from these vehicles [1]

   $50,089

   average price of a new US car in August, by Kelley Blue Book's count

   the first time over $50,000 since last December [2]

   What happened

   • The US Transportation Department finalised new fuel-economy standards for cars and light trucks on Monday. [1][2]
   • A fuel-economy standard sets how many miles a carmaker's new vehicles must go on a gallon of petrol, on average across everything it sells. [1][2]
   • For 2031 models, that average falls to about 35 miles a gallon, from 50.4 under rules set in 2024 under President Biden. [1][2]
   • The US Congress had already cut the fine for missing the standard to zero, so falling short costs a carmaker nothing. [1][2]
   • President Trump said the change would save families thousands of dollars on a new car. [2]
   • NHTSA, the US road-safety agency that writes the standard, estimated the change adds $185 billion to what people spend on fuel, Electrek reported. [1]
   • The same NHTSA estimate puts the rise in carbon from these vehicles at about 5%. [1]
   • Petrol averaged $4.47 a gallon in the US on Sunday, up from $4.09 a month earlier, as the war with Iran disrupts fuel supplies. [2]
   • Electric cars were 6.5% of new US vehicle sales in February, down from 7.4% across 2025, by the count of Edmunds, a car research firm. [2]
   • President Trump has also ended tax credits of up to $7,500 for people buying an electric car. [2]
   • The Sierra Club, a US environmental group, said it would fight the rule. [2]
   • The standards began after the Arab oil embargo of the 1970s and the energy crisis that followed it. [1][2]

   50.4 mpg2024 rules, 2031 cars

   vsvs

   about 35 mpgMonday's rules

   Who is involved

   • Sean Duffy the US transportation secretary; his department wrote the rule, and he said on Saturday it was coming on Monday
   • NHTSA the US road-safety agency that sets mileage standards; its own estimate puts the extra fuel spending at $185 billion
   • Donald Trump the US president; he said the rule would save families thousands of dollars on a new car
   • GM, Ford and Stellantis three of the biggest carmakers selling in the US; AP could not reach them, and carmakers in general say the rule widens the choice of petrol vehicles
   • The Sierra Club a US environmental group; it said the rule makes driving dearer and that it would fight it

   How it unfolded

   1. 1970s Mileage standards begin after the Arab oil embargo [1][2]
   2. 2024 Rules set under Biden aim for 50.4 miles a gallon by 2031 [2]
   3. Dec 2025 NHTSA projects about 34.5 miles a gallon under new rules [2]
   4. Before Monday The US Congress cuts the fine for missing the standard to zero [1][2]
   5. Sat 26 Sep Sean Duffy says the rule is coming on Monday [1][2]
   6. Mon 28 Sep The rule is finalised [1]

   Why it matters

   Watch whether the Sierra Club or other groups take the rule to court, and whether GM, Ford or Stellantis change the mix of vehicles they plan to sell, since missing the target already carries no fine. [1][2]

   The truth

   • What is really going on On Monday the US Transportation Department lowered the average mileage a carmaker's 2031 vehicles must reach, from 50.4 to about 35 miles a gallon.The US Congress had already cut the fine for missing that target to zero, so since then no carmaker has had to pay anything for falling short of the old number or the new one. [1][2]
   • Why it works on people The change was sold as savings on a new car, which President Trump put at thousands of dollars, and a price paid once in a showroom is easier to picture than extra petrol bought every week for years. [2][1]
   • Who gains GM, Ford, Stellantis and other carmakers — They can sell more petrol cars and trucks without missing a federal target, and missing it already cost them nothing. [1][2]
   • Who pays US drivers — Less efficient new cars burn more petrol per mile, and NHTSA's own estimate, reported by Electrek, is $185 billion more spent on fuel. [1]
   • Who pays People breathing car exhaust in the US — AP reports that without the 2024 rules, cars in 2035 could put out 90 more tons of soot a year and 4,870 more tons of the gases that make smog. [2]
   • Nobody knows yet

     What the final 2031 figure is.

     AP gave NHTSA's December projection of about 34.5 miles a gallon, and Electrek gave 34.9 from the proposal. We did not read the final text. [2][1]

   • Nobody knows yet

     What carmakers will actually build.

     With the fine already at zero, the standard no longer forces any mix of cars, and AP could not reach GM, Ford or Stellantis for comment. [2]

   • Nobody knows yet

     How much more petrol Americans will buy.

     NHTSA's own estimate, reported by Electrek, is $185 billion more spent on fuel. How much petrol is really burned depends on which cars people choose to buy, and nobody knows that yet. [1]

1. 02

   Hurricane Polo reaches Mexico's Baja coast

   What happened

   • Hurricane Polo bore down on Baja California Sur, a Mexican state on a long Pacific peninsula, on Monday as a Category 3 storm. [4][6]
   • Its winds were near 115mph, and the US National Hurricane Center warned of 15 to 30cm of rain, flash floods and mudslides. [4]
   • Water began to flood some streets along the coast on Monday. [7]
   • Officials said 90% of Puerto San Carlos, a fishing town of about 5,700 people, could flood. [6]
   • In Jalisco state, two children died after their home was swept away, and their parents are missing. [4]

   Why it matters

   After crossing the peninsula, Polo could hit mainland Mexico as a hurricane late on Monday or early on Tuesday. [4]

   San Juanico, a small fishing town in its path, has had electricity all day only for a few years and still loses it often. [6]

   The truth

   • Nobody knows yet

     How much damage Hurricane Polo did when it came ashore.

     Every report we read was written before landfall, and forecasters said it could hit mainland Mexico a second time late on Monday or early on Tuesday. [4][6]

1. 03

   A new kind of geothermal plant sells power

   What happened

   • Fervo Energy began selling electricity to the grid from Cape Station in Utah, the first time a large next-generation geothermal plant has done so anywhere. [8][9]
   • Older geothermal plants use hot water and steam that are already underground. [8]
   • Fervo uses drilling methods from the oil and gas industry to make its own reservoir in hot, dry rock, where water turns to steam. [8]
   • Its first 33-megawatt unit starts full commercial service this week, selling to Shell Energy. [8]
   • Fervo raised $1.9 billion when it listed its shares in May. [10]

   Why it matters

   Geothermal makes only 0.4% of US electricity, and it runs day and night. [8]

   Fervo told Canary Media its first phase would cost about $7,000 per kilowatt to build and the second about $5,500, against $2,157 for an average new US gas plant in 2025. [8]

   How it works

   What is underground is not a supply until someone can get it out

   Hot rock has always sat under southern Utah, and Fervo's oil-field drilling is what turned it into electricity for sale this month.

   The twist

   The heat under Utah is no bigger than it was a year ago. Fervo found a way to get it out at a price Shell Energy agreed to pay, and so it became electricity on sale in California.

   The picture

   Fervo, first phase$7,000 per kW

   Fervo, second phase$5,500 per kW

   Average new gas plant, 2025$2,157 per kW

   Step by step

   1. 1 Heat, metal and gas sit in rock deep underground
   2. 2 Most of it is too deep or too locked in to take out at a price anyone will pay
   3. 3 Then a method arrives, often from another industry, that makes getting it out cheaper
   4. 4 Once the cost falls below what a buyer will pay, a company drills and builds
   5. 5 From then on that rock counts as a supply, and buyers sign contracts for it

   The same force, elsewhere today

   Where this chain is also running, in today's other stories.

   • A new kind of geothermal plant sells power

     The heat under southern Utah was always there, and drilling methods from oil wells let Fervo make its own reservoir in hot, dry rock and sell the power.

   • Lithium from hot water under Cornwall

     Lithium is dissolved in hot, salty water deep under Cornwall, and a plant planned for 2029 would take out about 1,500 tonnes a year, helped by a government offer of nearly 10 million pounds.

   • Azerbaijan approves more gas from the Caspian

     SOCAR brought in ExxonMobil to run the search for oil and gas held in tight rock in the Middle Kura basin, fuel that ordinary wells cannot drain.

   Where you've seen this

   Oil in Texas shale

   oil held in tight rock sat untouched for decades, until drilling sideways and cracking the rock made it pay

   Sunlight on roofs

   it fell on every roof long before anyone used it, and became household power only once panels got cheap enough

   Old mine waste

   heaps of rock dumped as worthless get dug up again when a new process or a higher price makes their last bits of metal pay

   The catch

   A way to get something out does not make it cheap. Fervo's first plant is set to cost about $7,000 per kilowatt to build, more than three times an average new gas plant in 2025.

   And the whole of it

   A family in California buying power from Shell Energy, or a driver whose car battery may one day hold lithium from Cornwall, cannot tell which rock their energy came from. Which rocks get drilled is settled by engineers, lenders and governments that most of us never meet.

   The truth

   • Who gains Fervo Energy — Its first unit is selling power to Shell Energy, four months after a share listing that raised $1.9 billion. [8][9][10]
   • Nobody knows yet

     What Fervo's power costs the people who buy it.

     Fervo has not disclosed the prices in its contracts. Its own count is about 900 megawatts sold ahead at Cape Station, while Canary Media counts about 1,000 across its projects. [8][9]

   Good news

   • Fervo Energy's Cape Station in Utah began selling electricity to the grid, the first time a large next-generation geothermal plant has done so anywhere.

1. 04

   New York picks its first big battery projects

   What happened

   • NYSERDA, New York State's energy agency, picked eight large battery projects on Wednesday with 950 megawatts between them. [11]
   • They are lithium batteries that can each run for four to eight hours. [11]
   • They include a 150-megawatt battery in Suffolk County and the eight-hour, 140-megawatt Lighthouse project in Chautauqua County. [11]
   • The agency also chose 13 solar, wind and hydro projects with 719 megawatts. [11]
   • The state's goal is 6,000 megawatts of storage by 2030, and it pays each project only once it is running. [11]

   Batteries picked this week950 MW

   State storage goal for 20306,000 MW

   Why it matters

   The batteries would more than double the large-scale storage New York has built or contracted, the agency said. [11]

   The state has fallen behind its clean-power goals, and this year it changed its targets for cutting greenhouse gases. [11]

   The truth

   • Who gains Battery builders in New York, such as Key Capture Energy and Neoen US — Their projects won state contracts that pay once the batteries are running. [11]

   Good news

   • New York picked eight battery projects with 950 megawatts between them, enough to more than double the large-scale storage the state has built or contracted.
2. 05

   US limits solar imports before new tariffs

   What happened

   • The US Commerce Department issued an emergency rule capping imports of solar panels, cells, wafers and polysilicon, the purified silicon they are made from. [12]
   • From 4 December these imports pay a 15% tariff and must meet minimum prices. [12]
   • The rule is meant to stop importers bringing in far more than usual before that date. [12]
   • Importers registered after 6 August may bring in only 55 panels and 2,000 cells a week. [12]
   • Customs brokers who help anyone dodge the limits can lose their licences. [12]

   Why it matters

   Hanwha Qcells, which makes solar panels in the US, welcomed the rule. [12]

   Clean-energy trade groups and developers warn the tariffs will raise the cost of building solar farms and slow the move away from fossil fuels. [12]

   The truth

   • Who gains Hanwha Qcells and other US solar factories — The import caps stop rivals filling US warehouses with panels before the 4 December tariffs, and Qcells welcomed them. [12]
   • Who pays US solar farm builders — Clean-energy trade groups warn the tariffs and import caps will raise the cost of building solar farms. [12]
   • Nobody knows yet

     How many solar importers the US will stop.

     Commerce is comparing each importer with its past volumes and answering waiver requests within 14 days, but no count of blocked shipments was reported. [12]

3. 06

   EU warns 18 countries over sharing home power

   What happened

   • The European Commission sent formal letters to 18 EU countries, including France, Spain, Poland and Sweden, over an energy law agreed in 2024. [13]
   • The law lets households, small firms and public bodies share the renewable or stored power they make with other customers, and the shared power comes off those customers' bills. [13]
   • Countries had until 17 July to write it into their own laws and report it. [13]
   • The 18 have two months to answer, and the case can end at the EU's top court. [13]

   18 of 27

   EU countries sent letters

   Why it matters

   The letters are about failing to report, not a finding that the rules are missing: Spain and France already had schemes for sharing power people make themselves. [13]

   The Commission also wrote to 26 countries over a separate hydrogen and gas law, whose deadline only Italy met. [13]

   The truth

   • Nobody knows yet

     Which of the 18 EU countries have really brought in the right to share power.

     The Commission's letters are about failing to report the law, not a finding that it is missing, and Spain and France already had schemes. [13]

4. 07

   Britain's leader plans a state-owned grid company

   What happened

   • Andy Burnham, Britain's prime minister, was expected to announce Great British Grid, a publicly owned company to invest in the electricity grid, in a speech on Tuesday. [14]
   • It would compete with the three private companies that own Britain's main power lines to build connections for new power plants and businesses. [14]
   • Its money would come from the budget of GB Energy, the state-owned green energy company. [14]
   • Full details have not been set out. [14]
   • Ofgem, the energy regulator, estimates 70 billion pounds of grid investment is needed from 2025 to 2031. [14]

   Why it matters

   Burnham ties it to a goal of bringing UK energy costs into line with other European countries within ten years. [14]

   Some forecasts have household energy bills in Britain rising by about 500 pounds from January, and Unite, Labour's biggest union funder, has proposed a cap on energy prices. [15][16]

   The truth

   • Nobody knows yet

     What Great British Grid will cost and how it will work.

     Full details have not been set out, and Labour says it will be paid for within GB Energy's existing budget. [14]

5. 08

   Boston sues over a grant cut for car chargers

   What happened

   • Boston sued the US Transportation Department on Monday for cancelling a $20 million grant to rebuild three busy streets in Roxbury, a Boston neighbourhood. [17]
   • The department said the grant clashed with its priorities because the project included chargers for electric cars. [17]
   • The city says the chargers were less than 1% of the cost, and it offered to drop them. [17]
   • The department refused to restore the money, and says it is reviewing the lawsuit. [17]

   Why it matters

   Boston is the second city to sue over these cancelled grants: Albuquerque's case over an $11.5 million grant is still going. [17]

   The grants came from a 2021 infrastructure law signed by President Biden. [17]

   The truth

   • Who pays Roxbury, a Boston neighbourhood — It lost a $20 million grant for three busy streets because less than 1% of the project was chargers for electric cars. [17]
6. 09

   Azerbaijan approves more gas from the Caspian

   What happened

   • SOCAR, Azerbaijan's state oil company, TotalEnergies of France and XRG of Abu Dhabi agreed to fully develop the Absheron gas field in the Caspian Sea. [18]
   • President Ilham Aliyev said its second phase would raise Azerbaijan's gas output by about 5 billion cubic metres within three to four years. [18]
   • SOCAR also signed with ExxonMobil, the US oil company, to look for unconventional oil and gas, meaning fuel held in tight rock, in the Middle Kura basin. [18]
   • ExxonMobil will run that work. [18]

   Why it matters

   About half of Azerbaijan's 25 billion cubic metres of gas exports last year went to EU countries. [18]

   Selling Europe more would need new pipeline capacity, and Aliyev said oil and gas would keep leading the economy. [18]

   How it works

   SOCAR brought in ExxonMobil to run the search for oil and gas held in tight rock in the Middle Kura basin, fuel that ordinary wells cannot drain.

   The idea, in story 03: What is underground is not a supply until someone can get it out →

   The truth

   • Who gains SOCAR, TotalEnergies, XRG and ExxonMobil — They get more Caspian gas to sell, at a time when supply disruptions have made buyers worry about secure supplies. [18]
7. 10

   Lithium from hot water under Cornwall

   What happened

   • Geothermal Engineering, a company in Cornwall in south-west England, plans to spend about 43 million pounds on a plant that takes lithium out of hot, salty water from deep underground. [19]
   • It aims to start commercial production in 2029, making about 1,500 tonnes of lithium carbonate a year. [19]
   • That is enough for more than 180,000 typical electric-car batteries. [19]
   • The UK government has offered the project nearly 10 million pounds from a fund for the car industry. [19]

   Why it matters

   Lithium is used to make the batteries in electric cars, and demand for it is expected to rise 1,100% by 2035, the company said. [19]

   The plant would create nearly 50 jobs and support about 80 more, officials said. [19]

   How it works

   Lithium is dissolved in hot, salty water deep under Cornwall, and a plant planned for 2029 would take out about 1,500 tonnes a year, helped by a government offer of nearly 10 million pounds.

   The idea, in story 03: What is underground is not a supply until someone can get it out →
8. 11

   Dear loans slow clean power in poorer countries

   What happened

   • A study in Nature Climate Change looked at how much it costs to borrow for energy and industry projects in different countries. [20]
   • The computer models used to plan the world's carbon cuts usually assume every country borrows as cheaply as the safest ones. [20]
   • When the authors put in each country's own estimated borrowing rate, the price of keeping warming well below 2C rose by about 9% up to 2100. [20]
   • The cheapest cuts also moved to lower-risk regions. [20]

   Why it matters

   In the model, poorer countries got less money for their grids and made more of their central heat from gas. [20]

   Green hydrogen, made with clean electricity, came out dearer there, so it spread more slowly. [20]

   The truth

   • Who pays Poorer countries building clean power — In the Nature Climate Change study, their higher borrowing costs meant less money for their grids and dearer green hydrogen. [20]
9. 12

   The UN agrees a plan on rising seas

   What happened

   • The UN General Assembly in New York unanimously approved a resolution on how to deal with rising seas, Carbon Brief's daily digest reported. [21]
   • The US did not block it, although it mentions climate change and climate aid for poorer countries. [21]
   • In the same week, a fund aiming to raise $100 million to fight forest fires in South America was launched in New York. [21]
   • A report the same week found a gap of millions of dollars in money for protecting tropical forests. [21]

   Why it matters

   Grist, a climate news site, called the vote a rare win for countries acting together. [21]

   The fire fund leaves out large forests in Africa and south-east Asia. [21]

   Good news

   • The UN General Assembly unanimously approved a resolution on how to deal with rising seas.