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Doubters of the transition have always been quick to share doom scenarios about grids losing stability once wind and solar supplied a large share of their power. In the Energy Transition Show's early episodes, our host Chris noted how defenders of the status quo "have claimed for decades that the grid can't support more than 3 percent or 5 percent or 20 percent, it's a moving target, of variable renewables without risking blackouts…"

Years later, reality leaves transition skeptics less and less room to maneuver. So is there really an upper limit on how much wind and solar a grid can handle? In 2025, renewables provided more than 77% of South Australia's electricity generation, nearly half of it from wind. And for half an hour in April 2026, 98.8% of the power on Britain's transmission grid came from zero-carbon sources, by NESO's own measure.

Certainly along the way there have been blackouts blamed on renewables, such as 2016 in South Australia, or Spain and Portugal in 2025. If you only followed the headlines, you'd think the doubters had been right all along.

But grid engineers keep learning how to adapt, and the target keeps moving. In this episode of our documentary series, we start with conversations from the show's past and how they connect to recent ones about grid stability, including what the official investigation into Spain's blackout actually found, and how Britain gives its grid inertia without burning fuel.

Featured in this episode, in the order we hear their conversations, with titles as they were at the time of each recording:

Thanks to Fraunhofer ISE’s Energy-Charts Talk, Giordano Scarciotti and his Prof Gio channel, and Modo Energy’s Transmission podcast for permission to use their clips. Every clip in this episode is used with permission, under license, or from the public domain.

Over the summer, the IEA projected that carbon emissions from the world's power sector are on track for a new record in 2026. Electricity demand is expected to grow 20% faster than it did a year ago, and this year's gas shock has pushed some countries to use more coal.

But we're fresh off a new milestone for the energy transition. Last year, wind and solar grew enough to cover virtually all of the world's new electricity demand and fossil power fell, so emissions from power plants didn't rise.

So was last year a peak we can count on, or simply a pause? Over the Energy Transition Show's history, we've seen carbon emissions stall out before. In 2017, global emissions had barely grown for three years, and some thought that was it. But then they started to rise again.

How confident can we be that fossil power emissions are truly close to their peak? In this second episode of our documentary series, we follow that question through Chris Nelder's conversations with the analysts who have been tracking it, from 2017 to today. We'll hear the signs of a lasting decline versus a temporary dip, why emerging markets can stop fossil power from growing even if the coal plants they already have don't shut down, and why so much of the answer depends on what China does next.

Featured in this episode, in the order we hear their conversations:

When we first created the Energy Transition Show in 2015, solar generated about 250 terawatt hours worldwide. That was roughly as much electricity as California used the same year. A decade later, as the energy transition moved ahead, solar generates more than ten times as much, matching the European Union's total electricity demand.

Though sometimes progress can seem like it isn't happening nearly fast enough. Renewables only edged past coal in 2025, by supplying around a third of global electricity. But everything built over those ten years matters now more than ever. As we reviewed on Episode #272, soon after the US and Israel attacked Iran, the Strait of Hormuz closed, and the aftermath has created a persistent disruption in global energy flows that sent oil, gas and diesel prices surging. Ember's Global Electricity Review, which we covered with Nic Fulghum on Episode #274, found that the growth in solar generation in 2025 alone could displace gas-fired electricity equal to all the LNG exported through the strait that year. Without it, this crisis would be far harder to weather against the reality of constrained fossil fuel supplies.

For decades, forecasts for where the energy transition would be by now kept coming in low. Researchers from the LUT University team featured on Episode #95 went back through the International Energy Agency's World Energy Outlook reports and found they consistently underestimated solar. The IEA's most ambitious scenario from 2022 had annual solar installations peaking at 657 gigawatts in 2040. By SolarPower Europe's count, the world installed more than that in 2025.

This is the first in a new documentary series, built from our past episodes, featuring interviews Chris Nelder recorded while the future was still unfolding, often years ahead of the headlines. We start with Episode #200, where Canary Media's Jeff St. John co-hosted. They remembered how bold a name like "Energy Transition Show" seemed back in 2015. Were the forecasters just being too cautious, or were their methods off?

This year, some are projecting solar installations will fall for the first time in more than twenty years. What should forecasts like that tell us about the road ahead?

Featured in this episode, in the order they first appear:

Transportation continues to electrify, as a quarter of the world's new car market in 2025 was electric, both battery and plug-in hybrids. And this area of the energy transition is already showing up in metrics that matter for the climate. Recent data shows that running a battery electric car on Europe's grid cuts lifetime emissions by more than 70% against a comparable combustion car.

But even as progress on electrifying transportation continues, many other factors are holding back the deeper decarbonization we need. A switch to EVs won't remove traffic congestion on its own, or change how much of the street a passenger car consumes at the expense of smaller and lighter options. Vehicles turn over far faster than the streets they run on.

What can make our mobility system sustainable beyond the fuel? This is exactly the tension we were getting at in Episode #96. In this episode we return to our host Chris Nelder's 2019 conversation with Debbie Hopkins, now Professor of the Human Geographies of Mobility at the University of Oxford, who warned everyone working on the technology side. Swap the engine or change the fuel and you end up with the same unsustainable system.

When Chris and Debbie spoke, electric cars were about one in forty sold worldwide. Even though now it's one in four, that still won't get the job done as the energy transition's final answer. Transportation remains the single largest source of US greenhouse gas emissions, and it will take more than decisions about engines to tackle that.

The energy transition calls for more electrification. As transportation, heating, industry, and now power demand from data centers all crowd the interconnection queues, the US needs more transmission than it has built in generations. Even energy transition skeptics can agree on the wires.

But agreement on the need for more transmission has never been enough to get lines up and running. In 2019, journalist Russell Gold joined us to tell the story of Michael Skelly, who tried harder than anyone. His company, Clean Line Energy, spent a decade developing five major transmission lines to move wind power from the Midwest to the cities that needed it. His flagship line, the 700-mile Plains & Eastern, was fully permitted and offered the Tennessee Valley Authority twenty years of wind power at $18.50 per megawatt-hour, a price even the cheapest coal can't match. But economics aside, TVA walked away and not one of the five lines got built. Gold's book Superpower explains why engineering or economics weren't able to overcome the rules written state by state that build "regulatory moats" around the incumbents and keep the outsiders out.

Seven years since then, and those moats are where the race to tackle growing power demand is backing up. Recently ERCOT froze approvals of new data-center connections while the state audits an interconnection queue that has swelled to roughly 474 gigawatts of requested power capacity, more than five times the all-time peak power demand on the Texas grid. In Washington, FERC ordered the six regional grid operators it oversees to explain where the transmission for loads like that will come from. The specific fights are new but the overall mechanism is the one Russell Gold mapped with our host Chris Nelder back in Episode #98.

Since then, Grain Belt Express, the line Skelly had to sell on the way down, has grown into an $11 billion, 800-mile project with $1.7 billion in construction contracts signed. And Skelly has a new company working on the first large-scale connection between America's two big grids, a step toward the concept of Superpower that would tie the country's balkanized regional grids into one that could more readily support the energy transition's future.

Millions of Americans are sweltering under heat domes this summer, with temperatures soaring to record highs when weather systems stall. The grid feels the strain of these events too.

This extreme heat often creates a precarious situation that pushes electricity demand to levels never seen before, while forcing generation out of service. But why does summer weather get stuck like this in the first place? And is climate change making it happen more often?

For answers we can look to the North Atlantic jet stream, the high-altitude wind steering weather across North America and Europe. Our guest visualizes this as a ski-slope, where a steep gradient between temperatures keeps the jet racing fast and weather moving. Though, as the Arctic warms faster than the rest of the planet, the slope flattens, slowing the jet stream, which has it meandering in bigger waves. Slow weather becomes stuck weather. Whatever comes along, heat, rain, or drought, can then sit around for longer. Our host Chris Nelder dug into this mechanism in Episode #65, the ninth part of our climate science miniseries. That was back in 2018, years before "heat dome" became a household phrase.

In this conversation, recorded February 2018, Valerie Trouet, of the University of Arizona's Laboratory of Tree-Ring Research, explains how she reconstructed the jet's summer position back to 1725 from the density of tree rings in the British Isles and the Balkans. As the planet warmed, the jet lunged north and south far more often. Jet stream excursions like this have increased sharply since the 1960s, looking nothing like the natural climate variability of the three-century record.

Valerie Trouet shares with us how a five-millimeter core from a living tree reveals the climate's history. She also covers why the jet's slowdown makes more of an impact than how far it swings. Valerie's lab has continued publishing on this topic, and in a 2024 paper in Nature, her group took the reconstruction back to 1300 CE, reading jet behavior in seven hundred years of European harvest dates, grain markets, and mortality. Her former postdoc went even longer in a 2025 study tracing hemisphere-wide jet patterns across a full millennium, and so far, their frequency looks essentially unchanged on that extended timescale. Today's episode is one of our lagniappe releases, so the complete original conversation can be freely available for the entire Energy Transition Show audience.

The Statistical Review of World Energy 2026 is out, offering the first complete look at global energy data for 2025. The report's 75th edition, now presented in partnership with the energy think tank Ember, reveals a year in which demand for every form of energy hit a new record high.

But growing overall demand, even for fossil fuels, doesn't mean the energy transition isn't happening. Renewables grew more than any other form of energy for the first time outside of a recession, with solar power accounting for 72% of the increase. And global electrification reached a tipping point, with electricity demand growing 3%, faster than energy supply overall. China alone added the equivalent of Germany's entire annual electricity consumption in a single year. These are just a few of the indications that the future of global energy use is increasingly electric, even as regional paths differ.

In 2025, rising electricity demand was met entirely by low-carbon sources, with renewables and hydro overtaking coal as the largest source of generation. Fossil generation fell overall, demonstrating that fossil fuels are being substituted rather than supplemented.

Solar and storage are clearly taking the lead in the global energy system, and they're not looking back, as global battery storage capacity grew 66% last year alone. Solar already produces more electricity than gas in major parts of the world, and its lead in power generation will only grow.

In this episode, we are joined by Aditya Lolla, Interim Managing Director at Ember, and Euan Graham, Senior Electricity and Data Analyst at Ember and a lead author of the report, to share the key findings from this new update on all the energy data that matters.

We'll dig into the report's new total energy supply measure, which we explored in Episode #259. We'll hear how China's road fuel demand is now falling, redefining the assumed long tail of global oil demand. And we'll see why the whole global energy system now looks like it's collapsing toward a solar-and-battery regime.

Right now, Great Britain has more than enough new solar projects waiting to be connected to its distribution grid to meet its 2030 renewable energy target.

Italy and Poland could reach half their 2030 solar targets just by connecting the solar already sitting in their queues.

Across just eight European countries, there's a whopping 375 GW of wind and solar PV projects, and an even larger 455 GW of battery storage projects, just languishing in connection queues. Together, these wind, solar and battery resources are roughly equivalent to the entire generation capacity of those countries.

These are the shocking findings from a new study commissioned by the European climate nonprofit Beyond Fossil Fuels. Its estimates are deliberately conservative: the study values the trapped clean energy projects at around €100 billion, with the real total almost certainly higher. In this episode, we welcome Tara Connolly, their Programme Lead for Energy Markets and Grids, to share what the report found and learn what can be done about this sad state of affairs.

And the crunch isn't only on the supply side. Data centers are now muscling to the front of the same queues. In Ireland, they already consume half of greater Dublin's electricity, while households' EV chargers, rooftop solar, and home batteries wait behind them.

It will not surprise our longtime listeners at all to learn that unlocking all this mostly comes down to regulation, with many of the fixes already on the books, just not enforced.

It's taken a very long time to arrive, but next-generation geothermal power is finally becoming a commercial technology. Even though the virtues of geothermal have long been known and appreciated as clean, low-impact, and capable of running continuously, the few conventional geothermal installations in the US operating for decades supply less than half a percent of the nation's electricity. The promise of next-generation, "enhanced" geothermal, which we discussed back in Episode #248, is that it can be used almost anywhere. But business and technical challenges have held it back.

Until recently, that is. Now, several companies have overcome those challenges and are hard at work on new projects in the US and elsewhere, including Fervo Energy's Cape Station project in Utah, which is expected to begin delivering power this year and expand to 500 MW by 2028.

And the resource is significant: According to the IEA, the technical potential for next-generation geothermal wells less than 5 km deep in the United States is greater than 7 terawatts, a number that's more than five times the nation's total existing electricity generation capacity. The US Department of Energy projects that as much as 300 GW of that could be economically deployed by 2050, enough to meet up to 40 percent of anticipated demand growth. Some studies suggest that if new data centers are sited strategically, geothermal could power all of them. And costs are coming down fast. The IEA estimates they could fall by as much as 80 percent, which would make geothermal cost-competitive across the US. All that development would also create or preserve hundreds of thousands of jobs, many using skills that transfer directly from oil and gas extraction and fossil power generation.

To lay out the opportunity, the obstacles, and the state of the art in enhanced geothermal, we are pleased to be joined by Dr. Emily Pope, a senior fellow at the Center for Climate and Energy Solutions. Her report, Drilling Down—What it Will Take to Harness the Potential of Next-Generation Geothermal, was published in April and offers a comprehensive review of the sector. So if you gave up on geothermal years ago, this episode will show you what's changed.

This is the third and final part of our miniseries about South Africa's energy transition, based on Chris' travels there in September and October of 2025. The first part was Episode #264, in which we heard how the end of apartheid precipitated reform of the country's energy systems. The second part was Episode #276, where we learned how South Africa is reforming its electricity system from a state-owned monopoly to a free market, and from coal to renewables.

South Africa has enough wind and solar resources and land to generate at least three times as much power as its entire annual load, but the country is still locked into its old coal-fired electricity grid. Market reform is the key to unlocking that potential.

In this episode, we'll hear how those reforms can help deliver a just transition for South Africa, the most economically unequal country in the world. Because there, the energy transition isn't only about cheap, clean power; it's also a driver of economic justice. Today, some of the poorest households pay up to three times the grid price for electricity drawn through informal connections, and formalizing that power is a chance to deliver cheaper, fairer access to those who need it most.

We'll also learn how utilities and regulators across sub-Saharan Africa are working to integrate unsanctioned, distributed solar and storage into their grids. In South Africa, roughly 60% of those systems were never reported to the utility, and in Kenya the figure is effectively 100%. The economics are hard to argue with: the $1.7 billion Africa spent on solar panels last year is already meeting more demand than the $20 billion a year it spends on diesel fuel, with more than 85% of it self-financed. That bottom-up adoption is now transforming energy systems not only in South Africa, but across the entire region.