The U.S. solar industry installed 43.1 gigawatts-direct current (GWdc) of capacity in 2025, down 14% from 2024. GWdc is the nameplate rating of projects before they connect to the grid through inverters, which convert direct current (DC) to the alternating current (AC) our grid uses.

Two elements lower DC ratings to AC ratings. First, inverter losses account for around 4%.

More importantly, solar panels have specific output duration curves; there’s only a very small period when they produce maximum output, or even 80–90%. It’s uneconomical to buy an inverter that rarely hits full MW ratings, so developers resort to “solar clipping.” A 100 MWdc solar array might use inverters delivering a maximum of 80 MW of AC power to the grid. Typical DC/AC ratios are 1.1 to 1.25. You lose only a bit of energy on an MWh basis, but with significantly lower inverter costs. Therefore, MWdc numbers must be translated to the real-world MWac of the grid.

However, all capacity is not the same: a MW of solar capacity has two factors differentiating it from, say, a MW of gas-fired generation.

First, solar operates at a different capacity factor (a resource operating at 100% output all year would have a 100% capacity factor). An average panel capacity factor is 25%, compared to 60% for a combined-cycle gas plant. Because of this, it’s best to think in terms of energy generated. Location also matters; the capacity factor in Massachusetts is 16.5%, while in Arizona it is 29%.

One way to compare these is by energy output. Solar is now approaching 10% of total energy contributed to the grid. Additionally, solar arrays can be deployed faster than new turbines. With rising data center demand, we need all the electricity we can get.

(Source: https://www.eia.gov/todayinenergy/detail.php?id=67005)

Furthermore, solar is not dispatchable. It only generates power when the sun shines, while a gas plant can be called upon at any time, except during certain extreme weather events. In 2024, the mid-Atlantic grid operator PJM down-rated combined-cycle turbines from 96% to 79% in terms of their ability to meet peak demand during the worst hour of the worst day, and recently lowered that rating further to 74%. By comparison, PJM rates solar at only 7%.

When you hear about solar in terms of MWdc, it helps to reframe those values using the information above. Nonetheless, solar has grown considerably. In 2009, about 1 GW (1,000 MW) of solar was added in the U.S. That cumulative total is now 279 GWdc, and analyst Wood Mackenzie forecasts an increase of 490 GWdc over the next decade.

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Xcel Energy and Google recently announced a monumental clean energy agreement to power a new data center in Minnesota. While the deal includes massive wind and solar additions, the real game-changer is the energy storage component: 300 MW of iron-air batteries manufactured by Form Energy, boasting an unprecedented 100 hours of duration.

To put the scale into perspective, this single 30,000 MWh (30 GWh) project represents over 50% of the entire battery energy storage installed across the U.S. last year.

In our latest update, we unpack the details of this historic deal, including:

• The Iron-Air Technology: How the simple process of oxidizing (or rusting) cheap, abundant iron is being harnessed for grid-scale power.
• The Efficiency Trade-off: Why the market might be willing to accept a remarkably low 40% round-trip efficiency in exchange for the firm, dispatchable capacity required to balance variable wind and solar.
• Manufacturing Scale: How this single Google project will consume 60% of the 500 MW annual capacity at Form Energy's rehabilitated West Virginia steel mill.

Check out the full breakdown to explore whether this 100-hour battery is the key to solving the grid's resource adequacy challenges amid the booming, insatiable power demands of modern data centers.

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🎙️ About Energy Future: Powering Tomorrow’s Cleaner World

Hosted by Peter Kelly-Detwiler, Energy Future explores the trends, technologies, and policies driving the global clean-energy transition — from the U.S. grid and renewable markets to advanced nuclear, fusion, and EV innovation.

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I have spell-checked and fixed the grammar in the document's content. I've focused on corrections that maintain the original meaning and structure of the text.-----The last few weeks have seen numerous announcements by U.S. fusion energy companies.

First, let’s briefly explain fusion. With fission, you take a heavy and unstable nucleus and split it into two smaller nuclei, releasing energy and creating a chain reaction.

With fusion, you cause two light nuclei (usually hydrogen isotopes) to collide and merge into a heavier nucleus (such as helium), releasing energy. The sun is an enormous fusion reactor.

For commercial fusion, you need three things: 1) temperatures high enough (around 50 to 150 million °C) so nuclei move fast and fuse frequently; 2) sufficient density creating more opportunities for nuclei to collide, fuse, and release energy; 3) the ability to confine the reaction, keeping the plasma dense and hot enough to yield a net energy output.

Plasma itself is a state of matter in which a gas is highly energized so its atoms have lost one or more electrons, creating a mix of free electrons and ions.

Confinement of plasma can be achieved with the inertia of a compressed pellet or by using magnetic fields.

The pellet confinement approach - inertial confinement fusion, or ICF – is achieved by compressing a small fuel pellet (typically hydrogen) rapidly and with high density so it fuses before it can break apart.

With magnetic confinement, two main technologies exist: 1) tokomaks – donut shaped devices combining magnets with electric currents in plasma to construct a sort of magnetic cage; and 2) stellerators – machines employing magnetic coils that yield twisted magnetic fields requiring less currents in the plasma. Companies are pursuing approaches along these two main lines, with the majority using the magnetic approach.

The major recent technical achievement was Helion’s announcement that it had achieved plasma temperatures of close to 150 million degrees C.

On the commercial front, Type One Energy and the Tennessee Valley Authority are advancing licensing and construction plans for a 350 MW stellerator fusion plant, with groundbreaking as early as 2028.

Regarding licensing, Thea Energy received the first Department of Energy certification for its pilot stellerator design.

In financing, Avalanche Energy received $29 million in new investor funding, following significant breakthroughs in plasma physics, to support licensing, commercial-scale operations, and a test program. Avalanche is developing a tiny fusion reactor between 1 and 100 kW, “small enough to sit on your desk.”

Inertia Enterprises also raised almost $450 million to construct powerful lasers, as well as a power pla

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Hosted by Peter Kelly-Detwiler, Energy Future explores the trends, technologies, and policies driving the global clean-energy transition — from the U.S. grid and renewable markets to advanced nuclear, fusion, and EV innovation.

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