If Your Generator Has Never Run at Full Load... You Don't Know If It Will Perform When You Need It Most.
Load bank testing applies a controlled electrical load to a generator to simulate real-world operating conditions. It forces the generator to produce and sustain rated power, revealing any mechanical or electrical issues that do not appear at partial or no-load operation.
Stag supplies the generators and power distribution infrastructure required to conduct load bank testing wherever your facility or project is located. We work alongside your load bank provider or testing contractor.
How a Load Bank Test Is Conducted?
A complete test steps up in increments so performance at each level is verified before progressing. A full NFPA 110-compliant annual test requires a minimum of two continuous hours at 100% rated capacity.
Stages 1 & 2
25% – 50%
Warm-up and mid-load check. Confirms startup under load, establishes baseline operating temperature, and verifies voltage and frequency stability at half-load.
Stage 3
75% Load
High-load run. Engine response, cooling system performance, and fuel delivery are all confirmed under stress conditions before advancing to full load.
Full Compliance Test
100% Load
Full-load for a minimum of 2 continuous hours. Required for NFPA 110 annual compliance, new generator commissioning, and wet stacking correction.
NFPA 110 also requires monthly tests at 30% load for a minimum of 30 minutes. Facilities that only conduct monthly partial-load tests are at risk of wet stacking and undetected performance degradation.
The Cost of Skipping Load Bank Testing
What Happens When a Generator Has Never Been Tested Under Full Load
A generator that starts in under 10 seconds during a monthly test is not necessarily a generator that performs under full operating demand. Partial-load tests do not stress the engine, cooling system, or alternator to the levels required to expose hidden faults, and they actively cause wet stacking in diesel engines over time. Many generator failures are not caused by mechanical breakdowns but by undetected issues that only surface when the system is pushed to full capacity. When a real outage occurs, those hidden faults become real problems.
| Issue | Potential Cost |
|---|---|
| Wet Stacking Repair | Up to $2K–$8K |
| Hidden Alternator Fault | Up to $4K–$20K |
| Generator Failure During Outage | $25K–$100K+ |
When a generator fails under load, it often happens at the worst possible moment. The cost of an unplanned outage, including lost production, emergency response, and potential equipment damage, far exceeds the cost of routine full-load testing. Facilities that rely on partial-load or no-load tests may believe their backup power is ready when it is not. NFPA 110 mandates annual full-load testing precisely because partial-load tests are insufficient to verify true generator readiness.
Load bank testing applies a controlled electrical load to the generator to simulate real operating conditions, forcing the engine, cooling system, and alternator to perform at the levels they would face during an actual outage. This process identifies voltage instability, cooling deficiencies, fuel system issues, and alternator weaknesses before they cause failures in the field. Regular load bank testing also burns off wet stacking buildup in diesel engines, restoring proper combustion and extending engine life. For facilities with critical power requirements, it is one of the most important maintenance steps in a generator reliability program.
Stag supplies the generator and power distribution side. Contact Us to schedule your load bank testing setup wherever your operations run.
Monthly Testing vs. Annual Full-Load Testing
Not Sure What Testing Your Facility Requires?
NFPA 110 requires both monthly and annual testing. Both are mandatory, but they serve different purposes and require different equipment setups.
Annual Full-Load Test
NFPA 110 Compliance
2 continuous hours at 100% nameplate kW. Pre-test inspection, load data, and post-test sign-off required by code.
Burns Off Wet Stacking
The only way to burn off accumulated deposits from extended light-load operation. Restores full rated output and normal exhaust characteristics.
What Stag Supplies
Generator, iLine panel, distribution cables, and fuel for extended runs. Your load bank provider brings the load bank.
Monthly Partial-Load Test
30 Minutes at 30% Load
Minimum monthly requirement under NFPA 110. Log date, load level, duration, and any faults. Confirms startup and basic operation.
Wet Stacking Risk
Running exclusively at 30% load over time causes unburned fuel to accumulate in the exhaust system. Annual full-load test corrects this.
Who It Applies To
Hospitals, data centers, water utilities, emergency services, and any facility with a required standby system under NFPA 99, 101, or local code.
Rent a Generator for Load Bank Testing
Stag provides the generator and distribution infrastructure for your load bank test setup. We work alongside your testing contractor and can have equipment on site in as little as one day.
20kW
Smallest in fleet
2,000kW
Largest in fleet
Same-day
Dispatch available