A diesel generator will start and idle happily with nothing connected — and tell you almost nothing. The whole point of a generator is to carry real load the instant the grid fails, and the only way to prove it can is to make it. That is what a load bank test does, and skipping it is the most common — and most expensive — mistake used-genset buyers make.
What a load bank test is
A load bank is a device that applies a controlled, artificial electrical load to the generator — mimicking real demand without needing an actual building or process connected. The test ramps the genset up to a defined percentage of its rating and holds it there, so you can watch how the whole machine behaves under genuine stress.
What it proves
- The engine can make its rated power — not just idle, but pull load steadily without stalling, overheating or smoking.
- The alternator delivers clean, stable output — correct voltage and frequency under load.
- The cooling system holds temperature under sustained load.