As rising energy demands push the U.S. toward a massive power grid expansion, a new MIT study is offering insight into how different policy approaches could shape the nation’s energy future—balancing cost, emissions, and reliability in complex ways.

The research, conducted by a team from the MIT Climate Policy Center, analyzed federal legislation aimed at strengthening the national grid, including the BIG WIRES Act, which would require each transmission region to share at least 30 percent of its peak load capacity with others by 2035. The findings appear in Nature Energy under the title “Implications of Policy-Driven Transmission Expansion on Costs, Emissions and Reliability in the United States.”

The team modeled two main scenarios for nationwide grid expansion. One approach focused on building more infrastructure in regions with strong renewable energy potential, such as the Midwest’s untapped wind resources. The second, described as a “prescriptive” approach, envisioned a more evenly distributed grid buildout with stronger national interconnections.

Each strategy, the study found, offers distinct advantages. A regionally focused expansion would cost about 1.13 percent less and cut carbon emissions by 3.65 percent compared to the prescriptive model. However, the nationally interconnected grid could dramatically improve reliability—reducing power outages caused by extreme weather by 39 percent in some cases.

“There’s a tradeoff between the two things that are most on policymakers’ minds: cost and reliability,” said Christopher Knittel, an economist at the MIT Sloan School of Management and co-author of the paper. “The prescriptive approach ends up being better in the face of extreme weather and outages.”

To conduct their analysis, the researchers used MIT’s GenX energy generation model to simulate how legislative proposals, like the BIG WIRES Act, would influence future grid configurations. Results suggest that stronger national interconnections would help prevent crises such as the devastating Texas power outages in 2021 by ensuring electricity can flow across state lines during periods of peak stress.

“The U.S. grid is aging and it needs an upgrade,” said Juan Ramon L. Senga, a postdoctoral researcher at MIT’s Center for Energy and Environmental Policy Research and lead author of the study. “Implementing these kinds of policies is an important step to improve the grid, lower costs, lower emissions, and improve reliability. Some progress is better than none.”

Still, cost considerations remain significant. As Senga noted, an “optimized” grid that concentrates infrastructure near high-potential renewable zones may be cheaper—but only modestly so. “It’s not that much cheaper,” he said. “It’s single percentage points.”

The study also highlights the environmental dimension. As Knittel explained, building more connections near low-cost renewable resources tends to reduce emissions naturally. “Emissions fall when you let the optimizing action take place,” he said.

Ultimately, the team suggests a hybrid pathway may be the most practical—combining national interconnectivity mandates with regional buildouts around renewable hotspots. “You can find a balance between these factors,” Senga noted, “where you still have an increase in reliability while also getting cost and emission reductions.”

The research underscores the growing collaboration between academic experts and policymakers. “Working with legislation as the basis for academic studies can be productive for everyone,” Knittel added. “Scholars get to test their models in real-world scenarios, and lawmakers get evidence-based assessments of how their proposals might perform.”

The study’s authors include Senga; Audun Botterud, principal research scientist in MIT’s Laboratory for Information and Decision Systems; John E. Parsons, deputy director for research at MIT’s Center for Energy and Environmental Policy Research; Drew Story, managing director at MIT’s Policy Lab; and Knittel, the George P. Shultz Professor at MIT Sloa

A rapid global shift to renewable energy, energy efficiency and methane cuts could halve the rate of global warming by 2040, dramatically altering the world’s climate trajectory, a new Climate Action Tracker (CAT) assessment finds.

The analysis shows that implementing the three core COP28 energy and methane goals—tripling renewable energy capacity, doubling energy efficiency improvements, and delivering steep methane cuts by 2030—would bring down projected warming from the current 2.6°C to 1.7°C by the end of the century.

Crucially, these actions would sharply slow near-term warming, reducing the pace of temperature rise by a third by 2035 and nearly half by 2040, compared to today’s rate of ~0.25°C per decade. This slowdown is critical not just for long-term climate goals but for immediate survival, the report stresses.

A Turning Point

The world is already struggling to cope with accelerating climate impacts. With ecosystems collapsing faster than species can adapt and communities facing worsening heatwaves, storms and crop failures, “catching up” on adaptation has become a global emergency.

CAT warns that under current policies, warming could continue rising throughout the century, leaving governments perpetually behind on adaptation planning. But halving the warming rate would give both people and ecosystems a fighting chance to adjust.

A 0.9°C Improvement in the Global Outlook

If all countries implement the three goals, the resulting emission cuts—14 GtCO₂e by 2030 and 18 GtCO₂e by 2035—would reduce expected warming this century by 0.9°C, one of the most significant improvements since the Paris Agreement.

“This is the single biggest step governments can take this decade, using goals they have already negotiated and agreed to,” the report notes.

Where the Reductions Come From

• Tripling renewables: ~40% of total emission reductions
• Doubling energy efficiency: ~40%
• Methane cuts: ~20%, but delivering disproportionate warming benefits due to methane’s strong short-term impact

Finance Is the Missing Link

The report underscores that technology is not the barrier—finance is. Many emerging economies cannot deploy renewables or upgrade grids at the necessary pace without scaled-up international support.

Still, the authors say the pathway is feasible and grounded in technologies already available at commercial scale.

While the world is almost certain to overshoot 1.5°C by the early 2030s, the duration and magnitude of that overshoot will determine future levels of loss and damage. Delivering the COP28 energy and methane goals, the report concludes, is the most powerful tool the world currently has to limit that overshoot and avoid runaway climate impacts.

The world’s power sector is on the verge of a historic turning point, with no growth in fossil fuel generation expected in 2025 for the first time outside of a global crisis year, according to the latest Q3 Global Power Report by the energy think tank Ember.

Record-breaking increases in solar and wind power have met — and even exceeded — the rise in global electricity demand in the first three quarters of 2025, pushing fossil fuel use into stagnation.

“Record solar power growth and stagnating fossil fuels in 2025 show how clean power has become the driving force in the power sector,” said Nicolas Fulghum, senior data analyst at Ember. “Historically a growth segment, fossil power now appears to be entering a period of stagnation and managed decline.”

Solar Surges, Fossils Stall

Between January and September 2025, solar generation rose by 498 terawatt-hours (TWh) — up 31% year-on-year — marking the largest increase ever recorded over a nine-month period. Wind power added another 137 TWh, growing 7.6% compared to 2024. Combined, solar and wind generation expanded by 635 TWh, exceeding the global demand rise of 603 TWh (2.7%).

Nuclear output grew modestly by 33 TWh, while hydropower declined by 54 TWh due to unfavourable weather conditions. As a result, fossil fuel generation remained virtually unchanged, falling by 17 TWh (–0.1%) compared to the same period last year.

Ember forecasts that this balance will continue through the end of 2025, leading to the first year since the Covid-19 pandemic in which fossil generation does not increase despite global demand growth.

Clean Power Takes the Lead

The rise of clean power has reshaped the global electricity mix. In the first three quarters of 2025, wind and solar accounted for 17.6% of global electricity generation, up from 15.2% during the same period in 2024. Meanwhile, fossil fuels’ share fell from 58.7% to 57.1%.

All renewables combined — including hydro, solar, and wind — now supply 34.2% of global electricity, surpassing coal’s share for the second consecutive year.

China and India Tip the Global Balance

A fall in fossil fuel generation in China (–52 TWh, –1.1%) and India (–34 TWh, –3.3%) has been pivotal in keeping global fossil growth flat.

In China, the drop signals a structural shift, as fast-expanding solar and wind capacity met all new electricity demand.

In India, the decline is described as temporary, resulting from milder weather conditions that reduced cooling demand and allowed renewable generation to offset the slower rise in electricity use.

“China, the largest source of fossil growth, has turned a corner, signalling that reliance on fossil fuels to meet growing power demand is no longer required,” said Fulghum.

Demand Growth Decoupled from Fossil Fuels

Ember notes that 2025 is expected to record the sixth-largest increase in electricity demand in history — around 831 TWh — yet fossil generation remains flat. This marks the first time a significant rise in global demand has been met entirely by clean sources.

Prior to this year, falls in fossil generation occurred only during global downturns — in 2009 (financial crisis) and 2020 (pandemic lockdowns).

A Managed Decline Begins

Ember’s analysis concludes that fossil fuel power is entering a new phase of “managed decline,” driven by the accelerating deployment of clean energy and moderated electricity demand. The challenge, the think tank says, lies in sustaining renewable growth to achieve deeper cuts in fossil generation beyond 2025.

“Solar power has replaced fossil fuels as the dominant driver of growth in the power sector,” the report states. “The task now is to sustain this momentum in 2026 and beyond — not only to meet rising demand but to actively drive down fossil generation.”