Last Updated on February 16, 2026

Backup power systems — like generators — are essential for keeping businesses running during a power failure. Even a brief interruption can lead to significant costs and serious consequences for hospitals, data centers and manufacturing facilities, to name a few.

So, how can you be confident your generator will perform when it is needed most? How can you be sure the transition to backup power will be seamless and immediate?

The answer is by doing regular maintenance and a load bank test.

Load bank testing is vital to making sure your generator is running safely and ready to go when you need it most. Use this guide to refresh your skills and perform a load bank test safely.  

What Is Load Bank Testing and Why Is It Important?

A load bank is a device you connect to a generator to test the generator’s output. When you use a load bank to test your generator’s abilities, you’re performing a load bank test.

A load bank test simulates the demands of a real power outage, allowing you to evaluate the performance of your generator under controlled conditions. The load bank applies a controlled electrical load in stages, steadily increasing demand to maximum rated capacity. As it does so, it measures the generator’s ability to handle real-life emergencies.

• Learn More: What You need to Know About Load Banks

This process helps uncover potential issues before an actual emergency arises, ensuring your standby power system is ready to respond the moment it is needed.

Electrical load bank testing is also a key part of generator maintenance. For diesel-powered generators, it can reduce wet stacking, a problem where unburned fuel and soot build up in the exhaust system, reducing efficiency. Running a load bank test burns off these deposits and keeps the system running cleaner.

When Is Load Bank Testing Required?

Generally, you should run a load bank test at least once a year. However, you may need to test more or less frequently based on the use of the generator, criticality, regulations and manufacturer recommendations.

Organizations like the National Fire Protection Association (NFPA) and the National Electrical Code (NEC) mandate periodic load bank testing for certain industries, including medical facilities and data centers. For example, hospitals may need to conduct monthly load tests. Some insurance providers also make load bank testing a condition for coverage.

The NFPA 110 standard for emergency generators requires testing a minimum of two hours, with the generator running at 30% load for the first 30 minutes, followed by 50% load for another 30 minutes and then 100% load for an hour.

A Step-by-Step Guide to Load Bank Testing

Each generator and load bank setup can vary. However, there are general steps you should follow to ensure a successful, safe load bank test. Taking time to follow proper procedures protects both equipment and personnel, reducing the risk of accidents or damage. Follow these steps to safely perform a load bank test on your generator.

1. Review All Guidelines and Manuals

Before you turn on the generator and load bank, familiarize yourself with the performance and safety features of each. Review your equipment manuals and make sure you have proper training. If you’re renting equipment, ask your provider for safety training.

Then, review all local and national safety guidelines. This will include guidelines from the Occupational Safety and Health Administration and The Joint Commission for working with high-voltage or high-power testing to ensure a safe work environment and to maintain regulatory compliance.

• Pro Tip: Choose a load bank that’s rated for your generator to help prevent overloading and overheating.

2. Prepare the Generator and Inspect Equipment

Next, prepare the generator to make sure it operates efficiently. Check all fluid levels (fuel, oil and coolant) and top them off, if necessary.

Also, inspect the generator, cables, load bank and other equipment for wear or damage. Be sure to address any issues before continuing.

• Pro Tip: Disconnect other power sources, so the load bank test can get accurate readings.

3. Start the Generator

Turn on the generator and allow it to reach its normal operating temperature.

• Pro Tip: Pay attention to the sound of the machine. If it makes abnormal sounds or vibrates, turn off the power and address these issues before continuing.

4. Set Up and Connect the Load Bank

First, review the operator manual as load bank operation may vary by make or model. Then before you connect the load, select the correct voltage for the generator on the load bank.

Then, connect the cables between the generator and the load bank. Flip the master load switch on the load bank to the “on” position to begin applying the load to the generator.

• Pro Tip: Add loads incrementally. Do not add them all at once. Start with a low load and gradually increase it until the desired load level is achieved.

5. Check the Amperage and Voltage

Verify that the amperage and voltage displayed on the electrical load bank for each leg are accurate.

Check the amperage with an ammeter and voltage to neutral connection with a volt-ohm meter. At full load, the voltage for each leg should hold steady at 105-125 volts for a 110- or 220-volt single-phase generator.

To calculate draw, divide the generator’s rating in half and then divide it by the voltage from each leg. For example, a 10-kilowatt generator under a load of 110 volts should supply 45 amps per leg (10,000 kilowatts / 2 = 5,000 kilowatts / 110 volts = 45 amps).

6. Monitor the Load for Abnormalities

Conduct the test for the recommended duration, which generally ranges from about 30 minutes to several hours, depending on the size of the generator and the frequency of the tests.

As the test runs, keep monitoring the amps and volts. Also, keep listening for unusual sounds and looking for signs of overheating. Shut off the generator if a problem develops.

Document metrics like water or engine temperature, oil pressure, amps, volts and frequency.

7. Shut Down the Test and Record the Results

To end the test, gradually reduce the load from the generator. Allow it to run under a light load for one hour.

Then, remove all loads 5 to 10 minutes before shutting down the generator.

Allow both the generator and load bank to cool down before disconnecting the load bank.

• Pro Tip: Record the results of the test in your maintenance records. Good records are an essential element of preventive maintenance and can help reduce the need for repairs and prevent costly mechanical failure.

5 Load Bank Safety Tips

Working with electrical equipment always involves some level of risk, so stay mindful of your actions and make safety your top priority.

Keep the following load bank safety guidelines in mind:

1. Stay Grounded: Always ensure both the generator and load bank are properly grounded. A smart practice is to make grounding the first connection you establish and the last one you disconnect.
2. Use Well-Maintained, Properly Rated Equipment: Inspect all cables for wear and tear and insulation damage, and confirm they are phased and sized appropriately for the system. Install a circuit breaker or fuse at the power source, ensuring it is appropriately sized for the conductor run.
3. Keep the Area Clear: Operate the load bank in a clean, dry and well-ventilated location. Make sure there is ample space around the unit for unrestricted air flow and keep the area clear of debris. Prevent exhaust air from being drawn back into the load bank to avoid overheating.
4. Avoid Wet Conditions: Never use indoor load banks in wet conditions or during rain.
5. Use Personal Protective Equipment (PPE): Exercise caution when working near a load bank. The equipment generates high heat that poses a risk for burns. High noise levels can cause hearing damage and inhibit awareness of surroundings. Always wear appropriate personal protective equipment, which may include safety hard hats, gloves, eye and ear protection, high-visibility clothing and safety footwear.

Power Up with Electrical Equipment from Herc Rentals

Even generators need a little backup to ensure they are ready to save the day. An electrical load bank helps you test and support your generator so it is fully prepared to power through an emergency or keep your project site running smoothly.

At Herc Rentals, we have a load bank for every situation—from compact, portable models designed for indoor use to heavy-duty, trailer-mounted units built for outdoor applications. Our models are designed for easy setup, high-visibility display consoles and advanced safety features to minimize the risk of overloads.

Using a load bank from Herc Rentals can help you extend the life of your generator and keep it running correctly.

Browse our lineup of power generator and load bank rentals today, or call one of our specialists at 1-800-432-6215 to explore your options.