by Alex Marshall, Clarke Energy
The rapid growth of AI and high-density compute is reshaping how data centers think about power. Grid connections are slower, demand is spikier, and reliability requirements are rising. This has pushed developers toward onsite power stations that can operate for very different lengths of time – sometimes only minutes per year, sometimes thousands of hours.
Whilst many data center operators are familiar with back up diesel back-up gensets, gas engines sit at the center of this shift because they can move across those operating modes without changing the core technology. The distinction comes from how many hours the plant runs, how it interacts with the grid, and how it is integrated with the wider campus.
To understand the emerging “local power station” model for data centers, it helps to start with the three main operating bands: backup (<~100 hours/year), peaking (~1,000–1,500 hours/year), and long-run or “bridging power” (up to ~8,600 hours/year per individual engine). Each category has its own engineering and commercial logic—and data centers increasingly sit across all three.
1. Backup Power (<100 hours per year): Still Essential, but No Longer the Whole Story
Backup power is the familiar foundation of data-center resilience. Engines in this category typically run only for routine tests or rare grid outages. Historically these have been diesel engines, but natural-gas alternatives are gaining ground in urban and regulated markets where emission profiles are under scrutiny.
For short-duration operation:
- Reliability and fast start matter more than fuel efficiency.
- Maintenance is calendar-driven, not run-hour-driven.
- Fuel strategy is about assurance, not economics.
- Integration focuses on coordination with UPS systems to ensure seamless switching.
Where this becomes relevant to the modern data-center conversation is that backup power alone can no longer cover the sector’s needs. Sites increasingly require flexible capacity and the ability to run engines in export mode or extended-run scenarios. That is where the next operating band emerges.
2. Peaking and Flexible Generation Plants (1,000–1,500 hours per year): A Growing Category for Data Centers
Peaking mode is becoming a direct response to slow grid interconnections and the volatility created by high renewable penetration. Gas engines operating in this range can support two objectives at once:
- Covering data-center demand when the grid cannot, and
- Providing grid-support services that generate revenue or reduce site-level grid stress.
For this duty cycle:
- Start/stop frequency increases, making thermal management and oil-life monitoring important.
- Emissions controls become non-negotiable, particularly in urban US jurisdictions.
- Maintenance shifts to run-hour-based intervals, and parts wear due to frequent start-stops becomes a significant operating cost.
- Fuel efficiency becomes meaningful, though flexibility remains the primary design driver.
- Thermal recovery may be used for export or absorption cooling, improving PUE and reducing electrical load, but buffering would also be required to account for non-operating hours
The most important shift for data centers is that a 1,000–1,500-hour plant begins to act like a microgrid anchor rather than a last-resort backup system. It supports the grid during stress events, interacts with batteries for short bursts, and helps smooth the large load swings associated with AI compute clusters. Surplus installed, unused generating capacity can be used to support the grid. In certain jurisdictions such as Ireland and Texas, US, local grid operators may specify a requirement to “give back” and provide grid support in times of need.
3. Baseload and/or “Bridging Power” (Up to 8,600 hours per year per engine): The New Reality in Constrained Markets
In several US markets along with Ireland, Australia and the United Kingdom – developers are considering or tangibly deploying onsite base-load gas engine plants to allow large campuses to proceed while they wait for multi-year grid upgrades. These engines run nearly full-time, functioning as the primary power station for the site. Site continuous operation – 8,760 hours per year (24/7/365) can be achieved through adding redundant engines that can cover maintenance intervals of onsite engines.
In continuous-duty operation
- Fuel efficiency dominates the economics; every percentage point counts.
- Thermal recovery may be used for absorption cooling, improving PUE and reducing electrical load.
- Major overhauls must be scheduled years in advance, with clear windows for redundancy.
- Emission-control equipment scales significantly, including oxidation catalysts and, in some markets, SCR systems.
- Integration with large battery systems improves ramp rates and smooths transitions between onsite and grid power.
This is where the concept of “bridging power” becomes important. A plant may start as a baseload station, covering 100 percent of the compute load, but over time—once the grid upgrades are complete – the role changes either to back up, or flexible grid support operation.
4. How Bridging Power Transitions After the Grid Improves
Once a permanent utility connection is available, a gas-engine station built for baseload operation doesn’t necessarily shut down. It typically shifts into one of two long-term roles:
a. Transition to Backup and Resilience
A plant which contains individual engines that once ran 8,000 hours per year may drop to <100 hours, but the value remains:
- The engines already exist.
- The controls and switchgear are integrated.
- The maintenance team is trained.
- The site now has a far more robust backup system than a traditional diesel line-up.
- Emissions profiles are lower than diesel-fueled back up units
The result is a campus with a higher resilience standard and the option to ride through major grid events without risk.
b. Transition to Grid-Support and Peaking
Some campuses choose to continue running engines for 500–1,500 hours annually to provide:
- Demand-response services
- Frequency regulation
- Capacity-market participation
- Export during local grid shortages
- Supporting deployment of intermittent renewable energy
This creates a revenue stream that can offset operating costs and, in some cases, improves regional grid stability.
5. Engineering Considerations Across All Operating Bands
Regardless of the duty cycle, there are several constants that define how gas engines are designed for data-center use.
Fuel Strategies and Low-Carbon Pathways
Data centers can adopt natural gas, biomethane, or hydrogen-ready designs, depending on local availability and permitting requirements. As operating hours rise, fuel carbon intensity becomes more relevant, particularly for ESG reporting and customer pressure from large cloud or AI tenants.
Maintenance Anchors: Labor, Parts, and Lubricating Oil
These three pillars change drastically as run hours increase:
- Backup plants focus on periodic inspections.
- Peaking plants require higher-frequency oil changes and parts tracking.
- Baseload plants need fully structured long-term service agreements with overhaul planning.
Thermal Recovery and Cooling Interactions
Data centers produce enormous cooling loads. Engines running thousands of hours can support absorption chillers or drive combined cooling heat and power (CCHP) systems, reducing electric chiller demand and improving the site’s overall efficiency.
Space, Noise, and Air-Quality Constraints
Urban and suburban campuses must manage stack heights, NOx limits, noise levels, and spatial footprints. Higher-duty-cycle plants require more extensive acoustic treatment and emissions equipment.
Batteries and Controls
Gas engines pair well with batteries:
- Batteries cover first seconds or minutes.
- Engines sustain long-duration power.
- Advanced controls co-optimize both.
This pairing is particularly important for power for AI units with spiky loads along with peaking and bridging power.
6. Why Operating Hours Matter More Than Ever for Data Centers
Data centers are building power plants – not just backup lines. The same gas engine can:
- Run briefly for emergency protection
- Operate seasonally or during grid shortages
- Function as a temporary baseload station for multi-year periods
The determining factor is not the technology; it is the operating hours, the grid context, and the local regulatory environment.
As the US market accelerates toward onsite power deployments, understanding these operating categories helps developers, utilities, and regulators make better decisions about long-term planning, emissions impacts, and system integration. Gas engines provide a flexible bridge between the present and a future grid with higher renewable penetration, more electrification, and more demanding digital infrastructure.
