Generator Load Bank Calculator
What the Generator Load Bank Calculator does
The Generator Load Bank Calculator estimates the resistive load bank capacity needed to bring a generator to a chosen percentage of its rated real power. It accounts for any existing real load that will remain connected and stable during the test.
For example, a generator rated at 100 kilowatts (kW) has a target real load of 75 kW when tested at 75% of its rating. If a stable 20 kW load is already connected, the calculator estimates that an additional 55.00 kW of load bank capacity is required.
This calculation helps you plan the additional resistive load for a generator test. The result is expressed in kW, a measure of real power. It does not calculate reactive load, power-factor requirements, site derating, test duration, or manufacturer-specific testing procedures.
How to use the Generator Load Bank Calculator
Gather the generator’s applicable real-power rating, your desired test percentage, and the real load expected to remain connected throughout the test. Then enter the following values:
- Generator rated real power (kW): Enter the generator’s applicable real-power rating in kilowatts. For example, enter 100 for a 100 kW generator. The calculator accepts values from 1 to 100,000 kW.
- Target generator load (%): Enter the percentage of the rated real power you want the generator to carry. For example, enter 75 for a target of 75%. The allowed range is 0% to 100%.
- Existing connected real load (kW): Enter the real load that will remain connected and stable during the test. Enter 0 if no existing load will remain connected. The allowed range is 0 to 100,000 kW.
Read the Required Load Bank result in kW. The result is shown to two decimal places and represents the additional resistive load needed to reach the target under the calculator’s assumptions.
The default inputs are illustrative. For a planned test, use the rating and load figures that apply to your generator and operating conditions.
How the Generator Load Bank Calculator formula works
The calculator first finds the target real load by multiplying the generator’s rated real power by the target percentage. It then subtracts the existing connected real load:
Target real load (kW) = Generator rated real power (kW) × Target generator load (%) ÷ 100
Required Load Bank (kW) = Target real load (kW) − Existing connected real load (kW)
If the existing load already meets or exceeds the target, the calculator displays 0.00 kW. It does not return a negative load bank requirement.
Worked example
Assume a generator has a rated real power of 100 kW, the target load is 75%, and a stable 20 kW existing load will remain connected:
- Generator rated real power: 100 kW
- Target generator load: 75%
- Existing connected real load: 20 kW
- Target real load: 100 × 75 ÷ 100 = 75 kW
- Required Load Bank: 75 kW − 20 kW = 55.00 kW
In this example, the existing load and the added resistive load together reach the 75 kW target. The result depends on the existing 20 kW remaining connected and stable throughout the test.
As another illustration, a 500 kW generator tested at 100% with no existing load requires an estimated 500.00 kW of resistive load. If a 100 kW generator has a 25% target but already carries 30 kW, its target is 25 kW and the calculator returns 0.00 kW.
Use cases for the Generator Load Bank Calculator
The generator load bank calculator can help with several stages of test planning:
- Estimating additional load: Determine how much resistive load is needed when a known facility load will remain connected.
- Comparing target percentages: Enter different target percentages to see how the required capacity changes for the same generator and existing load.
- Planning equipment capacity: Use the result as a starting point when checking whether available load bank equipment has sufficient capacity.
- Considering a test with no facility load: Enter 0 kW for existing connected real load to estimate the load bank contribution needed to reach the entire target.
- Reviewing a proposed load: Check whether the expected existing load already meets or exceeds the selected target.
These estimates can support a discussion with the people responsible for the test. The calculation alone does not establish the correct test percentage, load sequence, or duration for a particular generator.
Other factors to consider when calculating Required Load Bank
Use the applicable kW rating. The calculator assumes that the generator rating entered is its applicable real-power rating in kilowatts. A rating expressed in kilovolt-amperes (kVA) is not the same input as a rating in kW. Confirm the appropriate rating for the planned operating conditions before relying on the estimate.
Account for changing facility loads. The existing connected real load is assumed to remain stable throughout the test. If equipment starts, stops, or changes demand, the combined generator load can differ from the target. Use a representative figure for the load that will actually remain connected.
Check site conditions and derating. The calculator does not adjust the generator rating for site derating. Conditions and equipment characteristics can affect the power available at a particular installation, so confirm the applicable rating separately.
Consider load bank increments. A calculated requirement such as 55.00 kW does not guarantee that an available load bank can be set to exactly that value. Select equipment with sufficient capacity and suitable load increments for the intended test.
Review reactive load and power factor separately. The result sizes resistive load in kW. It does not determine whether the test also requires reactive load or a particular power factor. Those requirements need separate consideration.
Follow the applicable test procedure. Load steps, test duration, connections, and manufacturer-specific procedures are outside this calculation. The appropriate test plan depends on the generator, installation, and purpose of the test.
Generator Load Bank Calculator FAQ
What does Required Load Bank mean?
It is the estimated additional resistive load, in kW, needed to bring the generator to the selected percentage of its rated real power after subtracting the stable existing connected real load.
Why does the calculator show 0.00 kW?
A zero result means the existing connected real load entered already meets or exceeds the calculated target. It indicates that no additional resistive load is needed to reach that target under the stated assumptions; it does not reduce an existing load that is above the target.
Can I enter a generator rating in kVA?
No. The input asks for generator rated real power in kW. Use the applicable kW rating rather than entering a kVA figure directly. The calculator does not convert kVA to kW or determine power factor.
What if the existing load changes during the test?
The estimate may no longer match the additional load needed to reach the target. The calculator assumes the existing real load remains connected and stable, so changing loads should be considered when planning and monitoring the test.
Does the result tell me the load bank size to select?
It provides a starting estimate for the required resistive load in kW. Check that the available equipment has sufficient capacity and suitable increments, and review any site derating, reactive load, and test procedure requirements separately.