People standing in front of a generator

How Do I Load Test a Generator?

Generators Must Be Tested


Critical backup generator systems must undergo strict generator load bank testing and commissioning on a regular basis. In the healthcare industry, American Society of Healthcare Engineers has determined that facilities “must inspect their emergency generators” on a weekly schedule and test under load on a monthly schedule

System inspections should include fuel checks (main and day tank levels, day tank float switch, fuel pressure, and any obstructions to piping, hoses, or vents), oil checks, validation of cooling systems, exhaust systems, and battery systems, as well as prime mover and generator components. (NFPA 110, Sec. 6-4.1) The regulations outlined here, while applicable primarily in the healthcare industry, give insight into the kind of protocols established in other industries that require load testing for generator backup systems

Let’s review a healthcare industry generator testing and commissioning procedure example. In it, we will look at testing programs and protocols for how to load test a generator so that you can know what to expect before testing your generator project.


Programs and Protocols


Every generator load bank testing operator should have a testing program in place that outlines the project’s goals and procedures. If we look at the healthcare industry’s use of load banks for generator testing, we find a good example of how testing and commissioning should follow explicit objectives, as well as an indication of optimal generator load bank testing frequency.


A comprehensive generator testing program, according to ASHE, should:


  • Train maintenance and clinical personnel to deal with power outages and interruptions
  • Test the functionality of equipment related to generator power
  • Test the mechanical and building system responses to outage
  • Test clinical equipment response to power failure or transfer
  • Minimize impact of testing on patient care and safety

Having clearly defined objectives such as these enables testing teams to keep their focus and remain goal-oriented throughout complex testing sequences

Protocols for generator load bank testing of generators tend to shift from one industry to another. But for the most part, protocols follow industry best practices and are somewhat standardized as generators typically employ the use of only two out of the three main types of load banks. When conducted properly, comprehensive testing and commissioning will give contractors greater confidence in backup power systems.

Testing begins by starting and running the generator(s) until voltage stabilizes. Then automatic transfer switch is transferred to the emergency power source. The generator load can then be increased in steps that simulate expected in the facility.


During the load test, the operator should observe the generator’s performance and check all system components for normal operation. These checks should include:


  • Does the system operate properly under the entire sequence of operation?
  • Does the system accept the load that is expected in operation?
  • Is power quality adequate under emergency power?
  • Are there any recurring engine alarms?
  • Are the voltage levels consistent?
  • Is the exhaust producing excessive smoke?
  • Are generator temperatures within normal ranges?
  • Is the transfer of fuel between the tank and the generator happening correctly?
  • Could the fuel be contaminated?
  • Do you detect any fuel or coolant leaks?

Be sure to address any alarms or alerts, should they pop up.

For comprehensive load testing, the generator must run at or near rated capacity for several hours. After conducting the test, remove the load bank first and return all transfer switches to their original state. Follow manufacturer guidelines to cool down the generator(s). Finish by logging information about all aspects of the generator load bank test, including time of testing, test conditions, and load size.




Proper use of load banks when testing generator sets can have great benefits for electrical systems undergoing the testing and commissioning process or regularly scheduled maintenance. Using load banks can help improve efficiency and cost-effectiveness by:

  • Simulating grid interaction, optimized around specific system needs and requirements.
  • Achieving speed, safety, and accuracy standards, purpose-built to your project.
  • Evaluating generator system performance with precision.
  • Creating customized, true-to-life testing environments representing scenarios verifying that each generator system is prepared to meet performance expectations.

As we have seen in the healthcare industry, following along a well-established set of goals and procedures ensures that any source of system failure, such as a faulty transfer switch or failed oil pump, can help system operators address issues before they arise in an emergency. In this case, testing and commissioning provides a controlled environment where a well-prepared staff can easily mitigate problems.