A load bank is a device that provides an electrical load to a power source, converting the generated electrical energy into heat, which is then dissipated into the atmosphere. Load banks are essential tools for testing, commissioning, and maintaining power generation and distribution systems across a wide range of industries.

What is a Load Bank?

At its core, a load bank is a precisely engineered resistive circuit designed to simulate real-world electrical demand. Resistive load banks convert electrical energy into heat through high-power resistor elements, cooled by forced air from industrial fans.

The most common type is the three-phase AC resistive load bank, where the power factor equals 1. All electrical energy is converted to heat with no reactive power component. Load banks range from a few kW to several MW.

There are three main types: Resistive load banks provide unity power factor and are the most common. Inductive load banks simulate motors and transformers with a lagging power factor. Capacitive load banks produce a leading power factor for testing UPS systems and non-linear loads.

Use Cases for Load Banks

Load banks serve a critical role across many industries where reliable power is non-negotiable. Below are the most common applications.

Power Generation Testing

Diesel generators, gas turbines, and other prime movers require regular full-load testing to verify performance and prevent wet stacking. Load banks apply a controlled electrical load, ensuring the generator reaches its rated output and operates at optimal temperature and pressure.

Data Center Commissioning

Data centers depend on uninterruptible power supplies (UPS) and backup generators to guarantee uptime. Load bank testing validates that the entire power chain performs correctly under full load before servers go live, including automatic transfer switches and cooling systems.

Grid Balancing and Frequency Regulation

Electrical grids must maintain a precise balance between generation and demand to keep the frequency stable at 50 or 60 Hz. Load banks can absorb excess power during periods of overgeneration, helping grid operators maintain stability and avoid frequency deviations.

Renewable Energy Integration

Solar and wind farms produce variable output depending on weather conditions. Load banks are used to test inverters, battery storage systems, and grid-tie equipment under realistic conditions, ensuring renewable installations perform reliably when connected to the grid.

Maritime and Offshore

Ships and offshore platforms rely on onboard generators as their sole power source. Load banks verify generator capacity and test switchboard protection systems in environments where failure is not an option.

Power Characteristics of a Resistive Load Bank

A resistive load bank behaves as a pure ohmic load: the power it consumes is proportional to the square of the applied voltage. For a three-phase system the total power is P = 3 x V² / R, where V is the phase voltage and R is the resistance per phase.

The graph below illustrates the power curve for a 1 MW three-phase resistive load bank. At the rated voltage of 400 V line-to-line, the load bank draws its full 1,000 kW. Because power follows a quadratic relationship with voltage, even a modest voltage drop significantly reduces the actual load. At 360 V the power output drops to approximately 810 kW, and at 300 V it falls to around 563 kW.

The current drawn by a resistive load bank is directly proportional to voltage (I = V / R). At 400 V, each phase carries approximately 1,443 A. Understanding these relationships is essential for sizing cables, breakers, and protection systems in any load bank installation.