Hydrogen Fuel Cells: Can They Replace Diesel in AI Datacenters?

Every AI campus hides a row of diesel generators behind the server halls, waiting for the grid to blink. They are loud, they are filthy, and their air permits get tighter every year. A growing list of operators wants to replace those engines with fuel cells, and some want to feed those cells hydrogen. Is that the clean backup plan the industry needs, or an expensive way to burn natural gas with a better press kit?

Before you read: We recently covered how AI’s appetite for electricity is pushing Big Tech toward dormant nuclear reactors. This piece looks at the other power path: electrochemical generators that skip combustion, and why hydrogen is much harder to deliver than the slide decks suggest.

Table of contents

• The Diesel Incumbent
• How a Fuel Cell Differs
• The Hydrogen Problem
• The Math of a 100-Megawatt Campus
• Fun Facts
• Where Hydrogen Actually Fits
• Sources

The Diesel Incumbent

Datacenters run on a strange contradiction. They are wired to the grid, yet designed to ignore it. Each site keeps banks of diesel generators sized to carry the full load until utility power returns, and most of the time those engines do nothing except pass a monthly test run.

The catch is that every generator is a small combustion plant with a smokestack. In many jurisdictions, non-emergency running hours are capped, so the most critical equipment on the site is also one of the most restricted. I think that is the real opening for fuel cells. Nobody gets excited about a fuel cell. Everybody gets excited about a backup system that does not start a permit fight every summer.

How a Fuel Cell Differs

A fuel cell does not burn anything. It runs a controlled electrochemical reaction in which hydrogen and oxygen combine into water, releasing electrons along the way. The principle is old. William Grove demonstrated it in 1839, long before anyone imagined a server rack.

Modern solid oxide fuel cells, like the units Bloom Energy sells to datacenter customers, typically convert roughly 50 to 60 percent of their fuel into electricity, and capturing the waste heat pushes overall efficiency higher. They are quiet and have no spinning parts to rattle the racks. In early 2025, American Electric Power announced plans to deploy up to one gigawatt of Bloom fuel cells to serve AI customers, a number that makes utility executives reach for a second coffee.

Here is the catch the press releases tend to bury: those units mostly run on natural gas today. Calling them hydrogen-ready means the stack can be adapted to hydrogen. It does not mean the box is sipping hydrogen right now.

The Hydrogen Problem

Hydrogen has the best energy-per-kilogram of any common fuel, about 120 megajoules per kilogram against roughly 44 for gasoline. The trouble starts when you measure by volume. Liquid hydrogen packs about 8 megajoules per liter, while gasoline packs about 32. The molecule that looks spectacular on a spec sheet turns into a tank problem very fast, and liquid hydrogen has to be kept at minus 253 degrees Celsius to stay liquid.

The supply chain is a problem too. Almost all hydrogen produced today comes from fossil fuels, and the International Energy Agency reports that less than 1 percent is low-emission. A campus that wants clean hydrogen is not just buying a fuel cell; it is betting on an electrolysis market that barely exists at scale. And the molecule is hard to keep. Hydrogen is the smallest molecule there is, so it seeps through seals and fittings that would hold other gases just fine. It is also flammable across a 4 to 75 percent concentration range in air, which makes leak detection a serious line item rather than a footnote. Anyone who has chased a slow leak in a bike tire knows the feeling, except the tire is the size of a warehouse and the gas can ignite.

Now run the round trip. Take solar power, push it through an electrolyzer, compress or liquefy the hydrogen, store it, and run it through a fuel cell. Multiply those efficiencies together and you land around 30 to 40 percent end to end, based on typical electrolyzer and fuel cell figures. A lithium-ion battery usually returns 85 to 90 percent of the energy you put in. Hydrogen storage is basically pouring water up a hill so it can run back down, except the bucket leaks.

The Math of a 100-Megawatt Campus

Run the numbers on a modest campus. A 100-megawatt facility running flat out for 24 hours uses 2,400 megawatt-hours. At 55 percent fuel cell efficiency, that means roughly 131 tonnes of hydrogen per day, using a lower heating value of about 33 kilowatt-hours per kilogram. That is more than a hundred tanker deliveries a day, assuming the hydrogen was clean to begin with. Somewhere, a logistics manager just aged a decade.

I think hydrogen makes real sense in two places: as long-duration storage on renewable-heavy grids, where you need to shift energy across weeks rather than hours, and where pipelines already exist. As the everyday fuel for a campus that needs near-perfect uptime, it is a much harder sell. The physics does not care about the press release.

Fun Facts

• NASA’s Apollo missions ran on hydrogen-oxygen fuel cells, and the water they produced was drinkable for the crew.
• A pure hydrogen flame is nearly invisible in daylight. Leaks are dangerous partly because you can walk straight into a fire you cannot see.

Where Hydrogen Actually Fits

The realistic near-term setup is a hybrid. Batteries cover the first seconds of an outage. Gas-fed fuel cells or diesel gensets carry the long hours. Hydrogen earns its place where the supply chain already exists, and the industry needs a few years of real operating data before anyone bets a gigawatt on it. Until then, the most honest hydrogen-powered datacenter is one that still mostly runs on natural gas.

Sources

• International Energy Agency: Global Hydrogen Review 2023
• U.S. Department of Energy, Alternative Fuels Data Center: Fuel Properties Comparison
• NASA: Apollo fuel cell history and hydrogen safety resources
• American Electric Power and Bloom Energy joint announcement (January 2025)
• Bloom Energy: Energy Server product specifications
• William Grove, 1839 (gas voltaic battery), historical record
• Round-trip and tonnage figures: author’s back-of-envelope calculations from typical electrolyzer (~65%), fuel cell (~55%), and hydrogen lower heating value (~33 kWh/kg) values