A 2,000 kVA generator idles under a 200 kVA building load for three years straight. The generator starts every month, runs for twenty minutes, and shuts back down.
Then the utility grid drops, and that same generator has to jump from 10% of its rated capacity to 90% in under ten seconds. That’s the first time it has ever been asked to do that, and it fails.
This is the gap a data center load bank exists to close. Backup generators and UPS systems get exercised constantly at partial load and almost never at the load they were actually sized for. A facility can pass every monthly generator test for years and still have no real evidence that the system holds up during a genuine, full-building outage. That’s why you need Load Banks.
Fast Facts: What You Need to Know About Load Banks
- A load bank is a controlled, adjustable electrical load used to test generators, UPS systems, and power distribution equipment at a specific, repeatable capacity.
- Uptime Institute’s 2024 survey found 54% of operators reported their most recent significant outage cost more than $100,000, and power issues remain the leading cause of serious data center outages.
- NFPA 110 requires supplemental load bank testing when monthly generator runs can’t reach 30% of nameplate capacity, specifically to prevent wet stacking and unburned fuel buildup in diesel engines.
- Different types of load banks (resistive, reactive, etc.) each simulate a different kind of real-world demand.
What A Load Bank Actually Does
A load bank draws power from a generator, UPS, or distribution system and converts it to heat, typically dissipated through a cooling system, at a level you control. That’s the whole function: it lets you apply a known, adjustable load on demand instead of waiting for real building demand or a real outage to reveal how equipment performs.
During commissioning, load banks can test generators, UPS units, HVAC, bus tracks, and power distribution units before a facility goes live. Without load banks, there isn’t usually enough real IT load yet to stress the system. During ongoing operations, load banks confirming that equipment sized for a full-building failure can actually deliver that capacity, not just the fraction of it that daily operations exercise.
If a generator almost always runs at 10-15% of its rated load, it’s easy to see that as a victor because you aren’t putting too much stress on your system. The problem with running at low capacity is that it may not work fully when you actually need it.
Running at low load causes incomplete combustion. This leads to wet stacking: unburned fuel and carbon build up inside the exhaust system. That buildup weakens performance right when you need full power.
The NFPA 110 standard helps teams navigate this. If your monthly tests never reach 30% of the generator’s rated capacity, you’re required to run an annual load bank test instead. This usually means running the generator at 50% load for 30 minutes, then 75% load for an hour. It clears out the buildup and proves the generator can actually hit full output.
How To Choose The Right Load Bank
Learning what type of load bank you need is the first step to a successful implementation
Resistive load banks simulate straightforward electrical demand, close to lighting and heating loads, and are the standard choice for baseline generator and UPS capacity testing.
Reactive load banks add inductive load, replicating motors, transformers, and other equipment with a lagging power factor, which matters if your actual facility load isn’t purely resistive.
Combination resistive and reactive units let you dial in a specific power factor to match your real load profile rather than testing against a simplified stand-in for it.
Mobile and container-mounted load banks extend this to sites without permanent test infrastructure, letting commissioning and periodic testing happen wherever the generator or UPS actually sits.
Testing Data Center Capacity Goes Beyond Power
Nobody in a data center takes a generator’s rated capacity on faith. You load bank it, you get the data, and only then do you trust it to carry the building. That instinct is still useful when the equipment in question is decommissioned instead of running.
Most ITAD vendors ask you to do the opposite: take a certificate of destruction at face value, the same way nobody would take a generator’s nameplate rating at face value. exIT Technologies applies the load-bank standard to Stilllegung von Rechenzentren, documented chain of custody from removal through final disposition, so what happens to the hardware is verified, not just claimed.
You wouldn’t run a facility on an untested generator’s word for it. There’s no good reason to run your asset disposition that way either.
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