Thank you, Matt, for giving us the chance to discuss your critique before taking this live. We appreciate the opportunity for a productive exchange, including a comprehensive feedback document and a direct conversation, and we're grateful for the care you put into this analysis. 

Before this report circulates widely, we want to offer context and explain where we substantively disagree.

We agree with Matt on more than the report suggests

In line with Giving Green’s core value of collaboration, we want to start by highlighting common ground, because there is more of it than the critique suggests.

We share Matt's view that variable renewable energy (wind and solar) will do the heavy lifting in the energy transition. No serious analyst believes otherwise, and neither do we. We also agree that other tools can be used in addition to clean firm power, such as energy efficiency or demand response, to meet growing demand and help modernize the U.S. electricity grid. 

Beyond electricity, we agree that transportation, food systems, and heavy industry are lagging sectors that deserve sustained philanthropic attention. Our portfolio reflects these priorities. The Giving Green Fund is broad: the majority of our planned 2025-2026 allocation supports high-impact nonprofit work on a global scale within food systems, heavy industry, and aviation and shipping. We expect to allocate about an additional quarter of our grantmaking to industry, energy, and possibly land use initiatives that are specifically in low- and middle-income countries. Likewise, our Unleashing Clean Energy—the strategy that encompasses all clean firm technologies—accounts for about a quarter of our portfolio, with nuclear-specific grants representing 1-2%. 

Figure 1: Expected 2025-26 Giving Green Fund grants by strategy

We also agree that the energy transition involves deep uncertainty. We do not think any single technology is the definitive answer, and when we do make grants supporting particular technologies, we likely have a good argument for doing so (for instance, capitalizing on a policy window of opportunity). Our Unleashing Clean Energy framework supports the policy and market conditions that allow the best solutions to emerge—whether that turns out to be long-duration energy storage (LDES), enhanced geothermal systems (EGS), carbon capture and storage (CCS), nuclear, or some combination. A portfolio approach is both more resilient and more honest about what we don't know.

Between 2023 and 2025, Giving Green’s nuclear-specific grants fell from 17.5% of a small $570K portfolio to 1.7% of $18.15M (as of early 2026), a sharp and deliberate shift that captures our evolution in supporting a wide portfolio of promising clean firm power technologies. 

Figure 2: Giving Green Fund nuclear and nuclear-adjacent grants as share of total grantmaking, 2023-2025

How much clean firm power do we need?

The report argues that excluding efficiency as a capacity resource makes the implications of the models in support of clean firm power weaker.

We continue to trust the three grid modeling studies we rely on—Baik et al. (2021), Cole et al. (2021), and Denholm et al. (2022)—which collectively suggest 700–900 GW of new clean firm capacity will likely be needed, representing roughly 20–40% of grid capacity on a net-zero grid. We acknowledge that these models use older cost assumptions and could benefit from more nuanced consideration of efficiency, and we welcome updated modeling. But the broader picture is more mixed than falling solar and battery costs alone suggest. There is a surge in AI data center buildout, growing civic opposition to large-scale renewable land use, and increased party-level polarization around renewables in the U.S. These forces increase the relative value of firm, dispatchable power.

The demand signal from major technology companies makes this growing value concrete. Hyperscalers like Microsoft, Google, and Amazon are not simply buying renewables plus batteries. They are signing long-term nuclear power contracts, investing in geothermal, and explicitly seeking around-the-clock firm power for data centers that cannot tolerate intermittency.

The underlying dynamic is as follows: at low to moderate penetration, adding renewables is cheap and displaces fossil fuels straightforwardly. But as renewable penetration rises, costs become increasingly asymptotic. The last 10–20% of decarbonization—filling seasonal gaps, providing grid reliability services, meeting firm 24/7 demand—is precisely where variable renewable energy (VRE) and short-duration batteries hit their limits, and where clean firm becomes essential. Reaching 100% clean energy is a hard constraint on which we simply cannot compromise. Where the cost curve bends depends on local factors such as land availability, transmission, and battery costs. But the logic of needing some firm capacity at high penetration is robust across most U.S. grid contexts.

Which clean firm technologies should we support?

We don't know which clean firm technologies will ultimately prove most viable, and we think that uncertainty is actually an argument for continued investment, not for withdrawal.

Every clean firm option has fundamental challenges. Long-duration energy storage still faces cost challenges and indirectly faces land use and social opposition challenges associated with VRE. Enhanced geothermal systems are promising but remain largely unproven at the commercial scale. CCS is still in early-stage demonstration and similarly faces cost challenges. Nuclear is a proven, widely deployed technology, but its primary challenge is cost, which is real and not fully resolved.

We find the asymmetry in the report's recommendations puzzling. If uncertain economics and unresolved challenges provide sufficient reason to deprioritize nuclear, the same logic would seem to apply to EGS and CCS, which are less proven. The report does not explain why nuclear should be singled out rather than all unproven or expensive clean firm options. Our view is that the uncertainty cuts the other way: because no single technology is a sure bet, eliminating any from the portfolio increases the risk that we reach high renewable penetration without the firm power needed to complete decarbonization.

Clean firm innovation to improve costs, prove technologies at scale, and build supply chains requires sustained investment now, not after the uncertainty resolves. Delayed action risks missing the window to build the knowledge base and industrial capacity that a net-zero grid will require. 

Where should philanthropy focus?

Given these dynamics, we think the distinctive role of philanthropy is to fund the long-term, high-risk work that private capital and government programs underinvest in.

Private actors have strong incentives to develop and deploy technologies once they are commercially viable. They have weaker incentives to build public trust, integrate equity and environmental justice, conduct independent policy research that may complicate deployment, or engage in the kind of long-term systems thinking that doesn't generate short-term revenue. Nonprofits fill that gap. Some of the organizations we support have pushed back against industry-favored policies, such as cost-overrun insurance for nuclear, precisely because independent analysis is what they are there to provide.

The report suggests that philanthropic support for nuclear duplicates existing private and government promotion. We disagree. The functions are genuinely different, and the counterfactual—a clean firm landscape shaped entirely by private and government actors without independent nonprofit input—is not one we think leads to better outcomes.

We also think the current policy environment creates a strategic opportunity. The Trump administration has been more favorable to nuclear and geothermal than to variable renewables, and a similar dynamic is playing out internationally following Russia's invasion of Ukraine. Working on clean firm policy during a window of political receptivity, even under an administration otherwise hostile to climate action, can advance long-term decarbonization goals in ways that would be harder to achieve later.

Planned updates and corrections

The critique prompted several updates to our published materials that we think are warranted. We plan to: (1) add nuclear cost as a counterargument in our UCE report alongside our best case for why the overall thesis holds; (2) clarify the provenance and limitations of the Bank of America/Idel (2022) figure; and (3) re-incorporate a balanced treatment of nuclear's co-benefits and risks that was inadvertently omitted when we archived our previous nuclear strategy report. We will note that omission on our mistakes page.

Since receiving our feedback document, Matt has corrected several errors about Giving Green and our history. We have agreed to disagree about a few remaining areas, which you can read more about in the feedback document linked at the top of this post. Some key examples:

• We think the report sometimes oversimplifies or, at times, mischaracterizes grid markets and required services.
• We interpret Cole et al. (2021) differently and don't believe their findings point to nuclear deployment increasing emissions.
• We are at odds with the assumption that countries near the tropics will not need clean firm power solely because solar radiation is more stable throughout the year.
• We find the analysis behind nuclear power increasing electricity rates misleading, as this is a challenge with electricity market policies and is not specific to nuclear power, especially in the case of Meta’s investment in Ohio.

We hope this response provides useful context for the report's publication and look forward to continuing to engage with experts and our followers to identify the most promising climate opportunities, especially as they relate to clean firm power.

— The Giving Green Team

Please note that it is unlikely we will respond to comments on this post, given capacity constraints.

For those who are interested in learning more, we are hosting a webinar on March 17 to dive deeper into our biodiversity research and recommendations.

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Hi, Vasco. Our research is focused on high-impact philanthropic strategies to slow greenhouse gas emissions and warming temperatures. So, this isn't our area of expertise. But you can find an analysis we recently read and discussed on the topic here: https://ourworldindata.org/part-two-how-many-people-die-from-extreme-temperatures-and-how-could-this-change-in-the-future

Thanks for sharing this thoughtful post on your giving journey, James. And thanks for everything you do. Everyone on the Giving Green team is excited to continue to follow your work.

Agreed, Felix! Thank for reading our updates.