Datacenter Standby Power: Key Considerations Amid Evolving Energy Dynamics

Datacenters are increasingly being asked, and in some regions are required, to participate in grid services like demand response (DR) using their standby generators. As electricity grids worldwide face increased pressure from renewable integration, electrification, and fluctuating demand, utilities and grid operators are turning to flexible demand sources to stabilize the grid. This overview highlights the landscape, drivers, and technical challenges for datacenters offering grid services with standby generators.

Datacenters are equipped with Uninterruptible Power Supplies (UPS) and standby generators, typically diesel or natural gas fired, to maintain uptime during grid outages. Additionally, datacenter networks are designed to transfer user traffic to other facilities in the rare event of an outage. It’s easy to assume that these features could be leveraged to reduce the datacenter’s demand on the grid during peak times, or even to provide additional generation if needed...however, it’s not that simple.

One common misconception is that datacenters can readily transfer user traffic to other facilities to reduce energy demand. In reality, this is a highly disruptive action, reserved strictly for emergencies. The feasibility of traffic diversion depends on the types of applications running within the datacenter. While some applications may allow for brief, minute long diversions, sustaining this for hours is generally impractical. Datacenter operators actively work to maximize infrastructure utilization and leaving IT hardware idle for extended periods is both economically inefficient and counterproductive to sustainability goals.

While standby generators can carry the datacenter load and reduce demand on the grid, there is a trade-off between performance, emissions, and efficiency. Generators are the last line of defense against power outages, ensuring continuous operations and safeguarding data integrity and must be reliable. For datacenter professionals, understanding the nuances of generator technology, including performance requirements, limitations, and the differences between diesel and gas generators, is critical to making informed design and operational decisions.

Until long duration energy storage (LDES), hydrogen fuel cells, and/or SMRs are available, we have limited choices for technology; diesel or gas (methane) reciprocating engines or turbines. Let’s look at the pros and cons of each:

Diesel

✅ Fast start time and transient response

✅ Fuel is stored on-site to refuel quickly, as needed

✅ Proven technology for emergency standby applications

❌ Fuel must be treated and stored and has a shelf life

❌ Emits more Sulphur, nitrogen oxide, diesel particulate matter, and carbon dioxide when burned

❌ Poor efficiency

Gas (methane)

✅ Compact size

✅ Burns cleanly with low emissions of carbon dioxide and nitrous oxide and no diesel particulate matter

✅ Costs less to generate the same amount of electricity (kwh) than diesel, not including capex

✅ Robust supply pipelines

✅ Ability to monetize by providing grid services

❌ Slower start time and load following. Large Combined cycle turbines can take up to an hour

❌ Must have access to natural gas pipelines

❌ Higher capital costs

❌ Slower start time and load following. Large Combined cycle turbines can take up to an hour

❌ Gas supply cold be curtailed in the winter when needed for home heat

Beyond the choice of fuel type, selecting the prime mover for standby power involves several considerations. Reciprocating engines are often preferred for standby power in datacenters due to their fast start-up time and lower initial cost. They perform well across a wide range of loads and are easier and cheaper to maintain, with widely available parts and expertise. However, they produce high emissions, particularly with diesel, and generate significant noise and vibration. Reciprocating generators are generally best for short, intermittent use and are less suitable for extended continuous operation.

In contrast, gas turbines offer high power density and are more compact, making them ideal for large-scale applications where space is at a premium. They produce lower emissions than reciprocating engines and operate with less noise and vibration, making them more compatible with neighbors and noise ordinances. Turbines also provide high inertia, which is critical for maintaining power quality during sudden datacenter load changes. However, turbines come with a higher initial cost, longer start-up time, and reduced efficiency at partial loads. They are better suited for continuous operation and longer grid services but require specialized maintenance.

There is a role for datacenters in supporting grid stability through demand response and other grid services, but alternate generator technology has to be considered. While traditional diesel standby generators were initially designed for emergency use only, datacenter operators and grid operators are exploring ways to leverage these assets more dynamically. However, there are technical, operational, and regulatory challenges that must be addressed to make this approach feasible and sustainable.

Datacenter operators must weigh the potential financial benefits of grid services against the increased wear on equipment, fuel logistics, emissions considerations, and operational complexities. Ultimately, the path forward will likely include a mix of traditional standby generation, renewable integration, battery storage, and advanced control systems, enabling data centers to meet their uptime requirements while supporting broader grid resilience.