Fuel cells, batteries, engines and solar for data centers: what each does

Gas turbines get the headlines, but AI data centers use a mix of power sources. Fuel cells and gas engines make steady power on site, batteries smooth sudden swings and bridge short gaps, and solar and wind supply energy mostly through the grid. Each does a different job, and none replaces the others alone.

When people say a data center is "powering itself", they usually mean a combination. This post separates the tools by the job each performs, using company announcements, an analyst tracker and regulator documents. Every figure is labelled with who said it and when. The post does not rank technologies or make predictions. For the turbine side first, read the post on gas turbine order books in 2026 and the wider overview of gas turbines and on-site power for AI data centres.

Key numbers at a glance

• Bloom Energy and Oracle, 13 April 2026: Oracle intends to procure up to 2.8 GW of Bloom fuel cell systems, with an initial 1.2 GW contracted and deployment continuing into 2027 (company statement; the 2.8 GW is an intention).
• Bloom Energy, 13 April 2026: a fully operational system delivered to Oracle in 55 days against an anticipated 90 days (company statement about a deployment in the prior year).
• Bloom Energy first quarter 2026, reported 28 April 2026: revenue of 751.1 million dollars, up 130.4 percent from 326.0 million a year earlier (company results).
• Bloom Energy, same release: full year 2026 revenue guidance of 3.4 billion to 3.8 billion dollars (company guidance).
• Bloom Energy, same release: related party revenue of 373.3 million dollars in the quarter (company results).
• Cleanview tracker, mid 2026: about 2.2 percent of the announced capacity operating, 1.2 percent under construction, 36 percent permitted and 60 percent announced or early stage (analyst tracker; headline totals are in the gas turbines and behind the meter power post).
• Cleanview, same report: Caterpillar 33 percent of permitted behind the meter capacity, over 8.8 GW, and Bloom Energy 14 percent (analyst tracker).
• Epoch AI, 17 April 2026: a developer describes the Port Washington, Wisconsin Stargate site as drawing 70 percent of its power from solar, wind and battery storage (analyst report quoting a developer description).
• Texas regulator docket 59220, 24 July 2026: a 525.5 MW emergency curtailment obligation on two co-located data centers behind one 265.5 MW wind facility (regulator decision as summarised by a trade newsletter).
• US Energy Information Administration, 6 October 2026 outlook: solar was 5 percent of US generation in 2024 and 7 percent in 2025, and is projected at 8 percent in 2026 and 9 percent in 2027 (government figures and projections).
• EIA, same outlook: Henry Hub natural gas spot price of 3.53 dollars per million British thermal units in 2025, projected at 3.48 dollars in 2026 (government figures and projection).

Start with the job, not the technology

Electric power has three jobs that people often mix up.

The first is energy: the total amount of electricity delivered over time, measured in megawatt hours. A data center that runs all day uses a great deal of it.

The second is capacity: the ability to deliver a certain amount of power at the exact moment it is needed, measured in megawatts. A data center needs capacity every hour, including the hours when the sun is down and the wind is still.

The third is quality and stability: keeping voltage and frequency steady, and riding through sudden changes. This is an engineering job measured in fractions of a second.

Different technologies are good at different jobs. Solar and wind deliver energy but only when the weather allows. Gas turbines, gas engines and fuel cells deliver steady capacity whenever fuel is available. Batteries deliver stability and short term capacity, and they can also move energy from one hour to another. Once you separate the jobs, the claim that one technology will "solve" data center power starts to look like three different questions.

Fuel cells: steady power in modules

A fuel cell converts fuel into electricity through a chemical reaction rather than by burning it to spin a turbine. Bloom Energy's systems are solid oxide fuel cells. Bloom's April 2026 announcement with Oracle does not state which fuel the systems use. Bloom is a US company that manufactures its systems in the United States, according to its first quarter release.

The Oracle announcement is the clearest public example of scale. Oracle intends to buy up to 2.8 GW of Bloom systems under a master services agreement. Only 1.2 GW is described as contracted, with deployment underway and continuing into 2027, so the larger number is an intention and not a commitment. Bloom says it delivered a fully operational system to Oracle in 55 days last year against an expected 90. That is a company statement, and it describes one deployment. It is evidence that fuel cells can be installed quickly, which is the main reason developers consider them. It does not tell you the delivery time for every project.

Bloom's own results show how fast the business is growing. The first quarter 2026 release reports revenue of 751.1 million dollars, up 130.4 percent from 326.0 million in the first quarter of 2025, and raises full year guidance to 3.4 billion to 3.8 billion dollars. Gross margin under US accounting rules was 30.0 percent. Two details are worth reading carefully. First, 373.3 million dollars of the quarter's revenue came from related parties, a category companies use for customers or investors with a close tie to the business. Second, the company lists as a risk factor any real or perceived slowdown in AI adoption that would slow data center expansion. Both are company disclosures, and they help a reader keep the growth in context.

Cleanview's tracker puts Bloom at 14 percent of permitted behind the meter capacity by manufacturer. That is a useful cross check: fuel cells are a real part of the mix, but well behind the combined weight of gas engines and turbines.

Gas engines: the workhorse option

A reciprocating engine is a piston engine, like the engine in a vehicle but far larger, driving a generator. These are common as backup generators and are also used for continuous power. The Cleanview tracker lists reciprocating engines among the technologies used in behind the meter projects, along with mobile gas generators, aeroderivative turbines and refurbished industrial turbines. It reports Caterpillar with the largest manufacturer share of permitted capacity at 33 percent, over 8.8 GW.

The case for engines is that they come in modest sizes, so a site can add units in steps and keep running if one is serviced. The case against is the one common to all on-site combustion: they need a gas supply, they produce air emissions, and each unit needs a permit. Published comparisons of engines and turbines on cost, efficiency and lead time vary widely by author, date and project size, so none is quoted here. If a source gives you such figures, check who wrote it, when, and for what size of plant.

Batteries: the shock absorber and the bridge

Batteries do not make energy. They store it. For a data center that is valuable in several ways.

AI training and inference loads can change quickly. The Mitsubishi Heavy Industries and Ingeteam announcement of 15 October 2026 says dynamic AI load profiles can cause harmonic distortion and voltage imbalance, which are power quality problems, and that longer grid interconnection timelines add to the challenge. Ingeteam's portfolio listed in that release includes battery energy storage and power electronics. The release is a memorandum of understanding and gives no financial terms or product timelines, so read it as a signal of the technical problem and not as evidence of a delivered product.

Batteries can also support a generator. A common design uses batteries to cover the seconds when load jumps, so that a turbine or engine can ramp up smoothly. The battery handles the fast part of the change and the generator handles the sustained part, which lets the site run fewer machines at partial load. How widely this design is used at AI sites is not documented in public sources in a consistent way, so treat it as an engineering pattern rather than a measured industry share.

On the grid side, batteries appear in several of the Stargate sites in the Epoch AI review of 17 April 2026. In Saline Township, Michigan, DTE Energy is described as supplying all the power, with a project financed battery storage system. In Milam County, Texas, SB Energy plans to fund and build new generation and storage for most of the campus. These are plans reported by an analyst and not operating results.

One more role is worth naming. Under Texas Senate Bill 6, large loads with on-site backup generation must disclose it to their utility, and the grid operator can direct them in an emergency to use the backup or to curtail. A battery could in principle help a site meet a curtailment request without turning on a generator. No named project has been publicly documented doing this, so it is a possibility, not an established practice.

Solar and wind: energy through the grid, and sometimes next door

Solar and wind produce energy without fuel, and developers use them in two ways.

The first is through the grid, by buying output under a contract or by siting near a project. Epoch AI says the developer of the Port Washington, Wisconsin site describes it as drawing 70 percent of its power from solar, wind and battery storage. The word "describes" matters: it is the developer's statement, and a share of "power drawn" is not the same as every hour being covered by those sources. Epoch also notes that Abilene draws on on-site natural gas plus grid power that includes local wind.

The second is physical pairing. An example appears in a Texas regulator docket decided on 24 July 2026, as summarised by the Global Data Center Hub newsletter. The Goodnight Wind facility in Armstrong County, Texas is an existing 265.5 MW wind farm. Its owner and Crusoe applied in January 2026 to net meter it with a 260 MW AI data center developed with Google. The commission imposed conditions on the arrangement: an emergency curtailment obligation of 525.5 MW across two co-located data centers, uncompensated, which the newsletter says is not capped by the paired generator's capacity. The data center load is as big as the wind farm, so the wind farm alone cannot cover it at all hours, and the rules respond to that by attaching curtailment duties to the pairing.

For national context, EIA's October 2026 outlook says solar provided 5 percent of US generation in 2024 and 7 percent in 2025, and projects 8 percent for 2026 and 9 percent for 2027. EIA also reported on 16 October 2026 that small scale solar generation had grown from 18,812 GWh to 92,979 GWh over a decade. Those figures show solar growing across the whole system. They do not say how much of any data center's load solar covers.

Why a mix, and why the mix is shifting

Look at the Cleanview numbers and the pattern is visible. Of the behind the meter capacity it tracks (see the gas turbines and behind the meter power post for the totals), only about 2.2 percent was operating in mid 2026 and 60 percent was still at the announcement stage. Cleanview estimates 2.8 to 3.2 GW operating by the end of 2026, and a range of 5 GW to 13 GW cumulative by the end of 2027 depending on delays. Plans move faster than steel.

That gap is why developers combine tools. A fuel cell block can be delivered in modules. A turbine block is cheaper per unit of power at scale but takes longer to obtain. Batteries and power electronics fill gaps. Grid power, including wind and solar contracts, supplies the bulk of the energy once the connection arrives. The Abilene campus, as described by Cleanview, shows the pattern: it is connected to the grid, built with on-site gas generation as well, and the turbines may start as primary power for training work before shifting toward backup. That last point is Cleanview's inference.

The mix also shifts with rules. Texas Senate Bill 6, according to its enrolled bill analysis, requires large loads of 75 MW or more to pay at least a 100,000 dollar study fee, show site control and commit financially to transmission, and requires disclosure of backup generation. It lets the grid operator direct backup generation or curtailment during an emergency, and says this does not require violating emissions or environmental laws. Rules like these change what developers choose, because an on-site machine that is backup today can be a grid support tool tomorrow.

Fuel prices matter too. EIA's October 2026 outlook puts the Henry Hub natural gas price at 2.19 dollars per million British thermal units in 2024, 3.53 dollars in 2025 and a projected 3.48 dollars in 2026, with 3.16 dollars projected for 2027. It also says rising production is offsetting growing liquefied natural gas exports. For a gas fuelled data center, fuel is a running cost, which makes these projections relevant. They are government projections and can change.

What is firm and what is uncertain

Firm, because a primary source states it:

• Bloom and Oracle announced a master agreement for up to 2.8 GW, with 1.2 GW contracted, in April 2026.
• Texas law and a regulator decision attach curtailment and disclosure duties to large loads and co-located generation.
• EIA reports and projects solar's growing share of US generation.

Uncertain:

• How much of the 2.8 GW Bloom and Oracle volume gets built, and on what schedule.
• The share of the behind the meter pipeline that reaches operation. Cleanview's own range for end of 2027 is wide.
• Cost per kilowatt for each technology. Published estimates vary by source, date and project, so none is quoted here.
• Whether battery plans reported by analysts at specific sites are built as described.
• The share of any site's energy that is truly from renewables over a year, as opposed to a developer's description.

What to watch next

• Bloom Energy's third quarter results, scheduled for 22 October 2026 according to its newsroom, for deployment volume and guidance.
• Whether Cleanview's operating capacity figure moves toward its 2.8 to 3.2 GW end of 2026 estimate.
• Further regulator decisions on co-located generation and curtailment in Texas, which set precedents for how pairing is treated.
• Detail from Mitsubishi Heavy Industries and Ingeteam on any battery and power electronics products for data centers.
• Whether more developers disclose hourly matching, not annual shares, when they say a site is powered by renewables.

Quick check

Sources

• Bloom Energy and Oracle expand strategic partnership to deploy up to 2.8 GW (Bloom Energy, 13 April 2026)
• Bloom Energy reports record first quarter 2026 results (Bloom Energy, 28 April 2026)
• Bloom Energy press releases (Bloom Energy, accessed 19 October 2026)
• Behind the meter data centers report summary (Cleanview, mid 2026)
• Stargate Abilene behind the meter entry (Cleanview, 2026)
• OpenAI Stargate: where the US sites stand (Epoch AI, 17 April 2026)
• Mitsubishi Heavy Industries and Ingeteam memorandum of understanding on data center power (Mitsubishi Heavy Industries, 15 October 2026)
• ERCOT data center interconnection pause and docket 59220 (Global Data Center Hub, 2026)
• Texas S.B. 6 bill analysis, enrolled (Texas Legislature)
• Short-Term Energy Outlook, October 2026 (US Energy Information Administration, 6 October 2026)
• Today in Energy index (US Energy Information Administration, accessed 19 October 2026)

Last reviewed: 19 October 2026.