What Powers the Grid for AI Data Centers

Where a data center gets its electricity depends on what powers the local grid. The generation mix determines how much electricity costs, how reliably it flows, and how much carbon it produces for AI infrastructure and data centers. In the US, natural gas generates 40% of all electricity, followed by nuclear (17%), coal (16%), wind (10%), solar (9%), hydropower (6%), and a remaining 2% from geothermal, biomass, and petroleum. ^{[1]Wolf Street, "US Power Generation by Source in 2025" (February 2026)https://wolfstreet.com/2026/02/24/whoosh-goes-demand-for-electricity-us-power-generation-by-source-in-2025-natural-gas-coal-nuclear-wind-hydro-solar-geothermal-biomass-petroleum/}

The US generation mix

In 2025, US power plants generated roughly 4,430 TWh (terawatt-hours, a standard unit for measuring total electricity output) of electricity, enough to power every home, business, and factory in the country. That was nearly a 3% increase over 2024 and a new record. ^{[1]Wolf Street, "US Power Generation by Source in 2025" (February 2026)https://wolfstreet.com/2026/02/24/whoosh-goes-demand-for-electricity-us-power-generation-by-source-in-2025-natural-gas-coal-nuclear-wind-hydro-solar-geothermal-biomass-petroleum/} Growing electricity demand from data centers and AI workloads is one of the forces pushing generation to new highs. ^{[2]IEA, "Data Centres and Data Transmission Networks" (2024)https://www.iea.org/energy-system/buildings/data-centres-and-data-transmission-networks}

The mix has shifted over the past two decades. In 2005, coal generated half of all US electricity. By 2025 its share had fallen to 16%, replaced primarily by natural gas and renewables (sources that replenish naturally: wind, solar, hydro, geothermal, and biomass). ^{[3]EIA, "What is U.S. electricity generation by energy source?" (accessed April 2026)https://www.eia.gov/tools/faqs/faq.php?id=427&t=3}

Natural gas more than doubled from 19% to 40%. Renewables grew from 9% to 26%, driven almost entirely by wind and solar expansion. Nuclear held roughly steady at 17-19% throughout, as a shrinking fleet (from about 104 reactors to 94) operated with fewer unplanned shutdowns and shorter refueling outages to maintain output.

The first force was cheap gas. Starting in the late 2000s, advances in hydraulic fracturing (fracking, a drilling technique that pumps high-pressure fluid into rock to release trapped oil and gas) unlocked vast reserves of shale gas (natural gas embedded in shale rock formations). That made natural gas the lowest-cost fuel that grid operators (the companies that manage electricity supply and demand across the power grid) can ramp up or down on demand.

The second was cheap renewables. Falling costs for solar panels and wind turbines made renewables competitive with fossil fuels in many regions, even without subsidies. ^{[4]Lazard, "Levelized Cost of Energy+ (LCOE+)" (June 2024)https://www.lazard.com/research-insights/levelized-cost-of-energyplus-lcoeplus/}

The timing matters for data centers: the shale gas boom and the data center boom overlapped. Cheap gas made cheap electricity, which made power-hungry computing more economical. Coal, once dominant because it was cheap and abundant, became uncompetitive on cost and faced tightening emissions regulations.

How to compare energy sources

Five metrics matter most when evaluating an energy source for data center power.

Cost (LCOE)

The levelized cost of energy (LCOE) is the total cost to build and operate a power plant over its lifetime, divided by the total electricity it produces, measured in dollars per megawatt-hour ($/MWh). It allows comparison across technologies with different capital costs, fuel costs, and lifetimes. ^{[4]Lazard, "Levelized Cost of Energy+ (LCOE+)" (June 2024)https://www.lazard.com/research-insights/levelized-cost-of-energyplus-lcoeplus/}

Capacity factor

Capacity factor is the ratio of a plant's actual output over a period to its maximum possible output if it ran at full power for the same period. A plant rated at 1,000 MW (megawatts) that produces 500 MW on average over a year has a 50% capacity factor. ^{[5]EIA, "Capacity Factors for Utility Scale Generators" (2024)https://www.eia.gov/electricity/monthly/epm_table_grapher.php?t=table_6_07_a}

Nuclear plants run above 90% because they rarely shut down. Solar panels average around 25% because they only produce when the sun shines.

Carbon intensity

Carbon intensity measures how much CO₂ is emitted per unit of electricity generated, in grams of CO₂-equivalent per kilowatt-hour (g CO₂e/kWh). The most useful measure is lifecycle emissions, which covers manufacturing, construction, fuel extraction, operation, and decommissioning. ^{[6]IPCC, "AR5 Working Group III: Mitigation of Climate Change, Annex III" (2014)https://www.ipcc.ch/report/ar5/wg3/}

On a lifecycle basis, coal is the highest at roughly 820 g/kWh. Natural gas is about 490 g/kWh. Nuclear and wind are both around 12 g/kWh, roughly 70x less than coal. Hydropower is about 24 g/kWh, and solar roughly 48 g/kWh. Even the highest non-fossil source emits less than a tenth of what coal does. ^{[6]IPCC, "AR5 Working Group III: Mitigation of Climate Change, Annex III" (2014)https://www.ipcc.ch/report/ar5/wg3/}

Dispatchability

A dispatchable source can increase or decrease output on command. Natural gas, coal, and hydropower are dispatchable: grid operators can ramp them up when demand rises and scale them back when demand falls. ^{[7]DOE, "What Generation Capacity Means" (accessed April 2026)https://www.energy.gov/ne/articles/what-generation-capacity}

Nuclear is technically dispatchable but in practice runs as baseload (always on, steady output) because its near-zero fuel cost makes full-power operation most economical, and thermal cycling (the stress of repeatedly heating up and cooling down) adds wear to the reactor. Solar and wind are not dispatchable because their output depends on weather.

For a data center that draws a near-constant load, non-dispatchable sources require either storage or a dispatchable backup to fill the gaps.

Speed to deploy

How long it takes to go from decision to operating plant. Solar and onshore wind farms can be built in 1-3 years. A natural gas combined cycle plant (a high-efficiency design that reuses waste heat, explained in detail below) takes 2-4 years. A new nuclear plant takes 10-15 years or more in the US. For a data center operator who needs power in 12-18 months, the fastest options are on-site gas turbines (months), solar farms (1-2 years), or battery storage (large banks of batteries that store electricity for later use, deployable in months to a year). ^{[8]EIA, "Cost and Performance Characteristics of New Generating Technologies, Annual Energy Outlook 2025" (2025)https://www.eia.gov/outlooks/aeo/assumptions/pdf/electricity.pdf}

Baseload, peaking, and intermittent

Electricity demand changes hour to hour. The grid layers different types of generation to match.

Baseload

Baseload plants run continuously at a steady output, covering the minimum level of demand that exists at all hours, including overnight. Nuclear plants are the classic baseload source because continuous full-power operation is most economical. Large natural gas combined cycle plants also serve as baseload when gas prices are low enough to justify running around the clock. ^{[7]DOE, "What Generation Capacity Means" (accessed April 2026)https://www.energy.gov/ne/articles/what-generation-capacity}

Peaking

Peaking plants fire up quickly to cover demand spikes, typically on hot afternoons when air conditioning drives consumption to its daily maximum. These are usually simple cycle gas turbines (based on jet engine technology, driving a generator) that can start in minutes but burn fuel less efficiently than combined cycle plants. About 25% of US power plants can start up within an hour. ^{[9]EIA, "About 25% of U.S. power plants can start up within an hour" (2020)https://www.eia.gov/todayinenergy/detail.php?id=45956}

Peaking plants run only a few hundred hours per year, so their cost per MWh is high. They fill a role that baseload and intermittent sources cannot: on-demand power at short notice.

Intermittent

Solar and wind generate electricity only when the sun shines or the wind blows. Their output cannot be controlled by grid operators.

Solar output follows a bell curve peaking at midday and dropping to zero at night. Wind output varies by hour, day, and season, though it tends to be stronger at night in many US regions, partially complementing solar. Intermittent sources are the cheapest per MWh but cannot guarantee power at any given moment without storage. ^{[4]Lazard, "Levelized Cost of Energy+ (LCOE+)" (June 2024)https://www.lazard.com/research-insights/levelized-cost-of-energyplus-lcoeplus/}

A data center's near-constant load aligns naturally with baseload sources, which is one reason nuclear and combined cycle gas are attractive for data center power. Intermittent sources can reduce average electricity cost but require either storage or grid-delivered backup.

Source by source

Natural gas

Combined cycle plants (which capture waste heat from the gas turbine to generate additional electricity via a steam turbine) are the workhorse of US generation. They produce about half the CO₂ of coal per kWh. ^{[6]IPCC, "AR5 Working Group III: Mitigation of Climate Change, Annex III" (2014)https://www.ipcc.ch/report/ar5/wg3/} Most data centers that draw baseload power from the grid are getting it from combined cycle gas.

On-site gas turbines are the fastest way to bring up behind-the-meter generation (power produced on-site that never passes through the utility meter). These are simple cycle turbines: a single gas turbine driving a generator, without the steam recovery stage that makes combined cycle plants more efficient. They start in minutes rather than hours, which is why operators choose them for rapid deployment despite the higher fuel cost per kWh. xAI deployed 422 MW of on-site turbines in Memphis in 2024, though the project drew regulatory scrutiny over air quality permits. ^{[10]Reuters, "Musk's xAI Memphis supercomputer churns without environmental permits" (September 2024)https://www.reuters.com/technology/musks-xai-memphis-supercomputer-churns-without-environmental-permits-2024-09-19/}

A related trend is co-location: building a data center physically adjacent to a power plant and drawing power directly. This avoids the grid bottleneck but has drawn regulatory scrutiny. In December 2025, FERC directed PJM (the Mid-Atlantic grid operator) to develop new rules for co-located facilities, requiring them to pay their fair share of grid costs rather than shifting those costs to other ratepayers. The ruling affects how co-located data centers are charged for transmission services they still benefit from, even if most of their power comes directly from the adjacent plant. Companies like GreenSparc and Crusoe Energy are pursuing variations on this model: Crusoe captures stranded natural gas (gas that would otherwise be flared or vented at oil well sites) to power modular data centers on location.

Nuclear

The US has 94 operating reactors that make nuclear the largest source of nearly carbon-free electricity in the country (12 g CO₂/kWh lifecycle, comparable to wind). ^{[1]Wolf Street, "US Power Generation by Source in 2025" (February 2026)https://wolfstreet.com/2026/02/24/whoosh-goes-demand-for-electricity-us-power-generation-by-source-in-2025-natural-gas-coal-nuclear-wind-hydro-solar-geothermal-biomass-petroleum/} The challenge is speed: new plants take over a decade to build and can cost tens of billions of dollars. The near-term opportunity for data centers is contracting with existing plants. Microsoft signed a 20-year PPA with Constellation Energy to restart Three Mile Island Unit 1 in Pennsylvania (the unit that was not involved in the 1979 partial meltdown, the worst nuclear accident in US history; Unit 1 operated safely for decades before closing in 2019 for economic reasons). The 835 MW plant, now renamed the Crane Clean Energy Center, is targeted for restart around 2028. ^{[11]Constellation Energy, "Constellation to Launch Crane Clean Energy Center, Restoring Three Mile Island Unit 1 to Power Microsoft" (September 2024)https://www.constellationenergy.com/newsroom/2024/Constellation-to-Launch-Crane-Clean-Energy-Center-Restoring-Three-Mile-Island-Unit-1-to-Power-Microsoft.html} Amazon tried a more aggressive approach at the Susquehanna nuclear plant in Pennsylvania: buy a campus next to the plant and draw power directly, bypassing the grid entirely. FERC (the Federal Energy Regulatory Commission) rejected the arrangement, partly because routing a large load behind the meter would shift grid costs onto other ratepayers. Talen Energy restructured the deal to sell Amazon power through the grid instead. ^{[12]ANS Nuclear Newswire, "FERC denies Talen-Amazon agreement, again" (April 2025)https://www.ans.org/news/2025-04-16/article-6937/ferc-denies-talen-amazon-agreementagain/}

Coal

No major US utility is building new coal capacity. Plants are retiring faster than they are being replaced, driven by the same cost and regulatory pressures described above. ^{[3]EIA, "What is U.S. electricity generation by energy source?" (accessed April 2026)https://www.eia.gov/tools/faqs/faq.php?id=427&t=3} Coal retirement reduces available baseload on the grid, tightening supply in regions that still depend on it.

Wind

Most US wind generation comes from onshore turbines concentrated in the Great Plains and Texas. ^{[13]EIA, "Electricity explained: Electricity in the United States" (accessed April 2026)https://www.eia.gov/energyexplained/electricity/electricity-in-the-us.php} Data center operators contract wind through PPAs (power purchase agreements), long-term contracts to buy electricity from a specific generator at a fixed price, to reduce average electricity cost and meet corporate carbon targets (public commitments to reduce or eliminate CO₂ emissions, driven by investor pressure, customer expectations, and in some regions, emissions regulations). But wind alone cannot serve a 24/7 load because its output depends on weather conditions that vary hour to hour.

Solar

Solar is the fastest-growing source of new capacity, with roughly 70 GW (gigawatts, equivalent to about 70 large power plants) of new projects scheduled to come online in 2026 and 2027. ^{[14]EIA, "Solar power generation drives electricity generation growth over the next two years" (2026)https://www.eia.gov/todayinenergy/detail.php?id=67005} But at a ~25% capacity factor, that 70 GW of rated capacity delivers only about 17-18 GW of average output. Solar is cheap and fast to deploy but only generates during daylight hours. Pairing solar with battery storage or a gas backup is increasingly common for data center projects that need round-the-clock power.

Hydropower

Most US hydropower comes from dams built decades ago in the Pacific Northwest and along major river systems. The best sites are already built out, and new large-scale hydro is unlikely in the US. Where available, hydro from dam reservoirs is excellent for data centers because it is both dispatchable and nearly carbon-free (24 g CO₂/kWh lifecycle). Oregon and Washington benefit from cheap hydro, which is one reason the Pacific Northwest has attracted data center development. ^{[13]EIA, "Electricity explained: Electricity in the United States" (accessed April 2026)https://www.eia.gov/energyexplained/electricity/electricity-in-the-us.php}

Geothermal and biomass

Together, geothermal and biomass account for less than 2% of US generation. ^{[3]EIA, "What is U.S. electricity generation by energy source?" (accessed April 2026)https://www.eia.gov/tools/faqs/faq.php?id=427&t=3} Traditional geothermal taps volcanic heat in regions like Nevada and Northern California. Enhanced geothermal systems drill deep enough to reach naturally heated rock formations far below the surface, making geothermal power possible in locations without volcanic activity. ^{[15]DOE, "Enhanced Geothermal Shot" (accessed April 2026)https://www.energy.gov/eere/geothermal/enhanced-geothermal-shot} These systems are in early commercial development, but if enhanced geothermal scales, it could provide the dispatchable, nearly carbon-free baseload that data centers need, deployable in locations where traditional geothermal is not an option.

Biomass power is generated by burning organic material: wood waste, agricultural residues, and landfill gas. It accounts for less than 1% of US generation.

Backup generation

Every data center has backup power regardless of how it connects to the grid. If the grid goes down or the primary power supply fails, backup generators keep the facility running long enough to ride through the outage or shut down gracefully. Backup generation is distinct from grid-level generation. It sits on-site, behind the meter, and exists solely for resilience.

Diesel generators

Diesel generators are the standard backup for most data centers. When grid power fails, UPS (uninterruptible power supply) batteries take over instantly, providing 5-15 minutes of runtime. Within that window, diesel generators start and reach full load in 10-15 seconds, then take over from the batteries. A large facility might have dozens of diesel generators, each rated at 2-3 MW. ^{[16]Uptime Institute, "Data center diesel generators: frequently asked questions" (2024)https://journal.uptimeinstitute.com/data-center-diesel-generators-frequently-asked-questions/}

The constraint is runtime. Diesel generators are designed for short emergency runs. Most air quality permits limit runtime to a few hundred hours per year. On-site fuel storage typically provides 24-72 hours of operation. Beyond that, the facility needs fuel deliveries or must find alternative power. ^{[16]Uptime Institute, "Data center diesel generators: frequently asked questions" (2024)https://journal.uptimeinstitute.com/data-center-diesel-generators-frequently-asked-questions/}

Natural gas generators

Some facilities use natural gas generators as backup instead of diesel. Gas generators produce fewer emissions and can run longer since they draw from a pipeline rather than a finite fuel tank.

But pipeline supply can be disrupted during the same extreme weather events that cause grid failures. During the February 2021 Texas winter storm, widespread natural gas infrastructure failures coincided with surging electricity demand, leaving millions without power for days. ^{[17]FERC/NERC, "The February 2021 Cold Weather Outages in Texas and the South Central United States" (November 2021)https://www.ferc.gov/media/february-2021-cold-weather-outages-texas-and-south-central-united-states-ferc-nerc-and} Some operators install dual-fuel generators that can run on either gas or diesel to mitigate this risk.

The shift toward batteries

Some operators are beginning to replace diesel generators with battery systems or use batteries alongside diesel in hybrid configurations. Batteries respond faster than generators (milliseconds vs. seconds), produce zero on-site emissions, and avoid the permitting constraints that limit diesel runtime. The limitation is duration: most grid-scale battery systems are sized for 4 hours of storage, far less than the 24-72 hours a diesel tank provides. ^{[18]EIA, "Battery Storage in the United States: An Update on Market Trends" (2024)https://www.eia.gov/analysis/studies/electricity/batterystorage/}

What this means for data centers

No single source checks every box. Nuclear runs continuously and is nearly carbon-free but is expensive and slow to build. Combined cycle gas is cheaper and faster but produces carbon. Solar and wind are cheap and clean but cannot guarantee power at any given hour. Storage can bridge the gap, but grid-scale battery storage is typically sized for 4 hours, not the days-long outages that extreme weather can produce. ^{[18]EIA, "Battery Storage in the United States: An Update on Market Trends" (2024)https://www.eia.gov/analysis/studies/electricity/batterystorage/}

Corporate carbon commitments add another dimension. Most major hyperscalers (the largest cloud and AI operators: Google, Microsoft, Amazon, Meta) have published net-zero or 100% renewable energy targets. ^{[2]IEA, "Data Centres and Data Transmission Networks" (2024)https://www.iea.org/energy-system/buildings/data-centres-and-data-transmission-networks}

That pulls procurement toward solar, wind, and nuclear PPAs. But reliability requirements pull toward natural gas. ^{[19]Hanwha Data Centers, "Power Availability: The New #1 in Data Center Site Selection" (2025)https://www.hanwhadatacenters.com/blog/power-availability-the-new-1-in-data-center-site-selection/}

Geography determines the available mix. A data center in the Pacific Northwest draws from a grid rich in hydro and wind. A facility in PJM (the regional grid operator covering the Mid-Atlantic and parts of the Midwest) relies heavily on natural gas and nuclear.

A site in ERCOT (the Texas grid operator) has access to cheap wind and gas but faces isolation risk since ERCOT is largely isolated from the rest of the US grid, connected only through a few small direct-current links.

References

1. Wolf Street, "US Power Generation by Source in 2025" (February 2026)
2. IEA, "Data Centres and Data Transmission Networks" (2024)
3. EIA, "What is U.S. electricity generation by energy source?" (accessed April 2026)
4. Lazard, "Levelized Cost of Energy+ (LCOE+)" (June 2024)
5. EIA, "Capacity Factors for Utility Scale Generators" (2024)
6. IPCC, "AR5 Working Group III: Mitigation of Climate Change, Annex III" (2014)
7. DOE, "What Generation Capacity Means" (accessed April 2026)
8. EIA, "Cost and Performance Characteristics of New Generating Technologies, Annual Energy Outlook 2025" (2025)
9. EIA, "About 25% of U.S. power plants can start up within an hour" (2020)
10. Reuters, "Musk's xAI Memphis supercomputer churns without environmental permits" (September 2024)
11. Constellation Energy, "Constellation to Launch Crane Clean Energy Center, Restoring Three Mile Island Unit 1 to Power Microsoft" (September 2024)
12. ANS Nuclear Newswire, "FERC denies Talen-Amazon agreement, again" (April 2025)
13. EIA, "Electricity explained: Electricity in the United States" (accessed April 2026)
14. EIA, "Solar power generation drives electricity generation growth over the next two years" (2026)
15. DOE, "Enhanced Geothermal Shot" (accessed April 2026)
16. Uptime Institute, "Data center diesel generators: frequently asked questions" (2024)
17. FERC/NERC, "The February 2021 Cold Weather Outages in Texas and the South Central United States" (November 2021)
18. EIA, "Battery Storage in the United States: An Update on Market Trends" (2024)
19. Hanwha Data Centers, "Power Availability: The New #1 in Data Center Site Selection" (2025)