Standby Generator Monthly Exercise and Load-Bank Testing

A standby generator’s whole job is to work on the worst day. The only way to know it will is to exercise it regularly under load and load-bank test it periodically. A generator that “runs fine” at no load can still fail when real demand arrives.

Exercise it monthly — under load

Most standby units are set to auto-exercise weekly or monthly. The critical detail: it needs to run under load, not just idle. A transfer-switch test that actually carries the building load (or a load applied another way) brings the engine to proper operating temperature and confirms the whole system — engine, alternator, transfer switch, and controls — works together.

What wet stacking is

When a diesel generator runs lightly loaded or at no load for extended periods, it never reaches full operating temperature. Unburned fuel and soot accumulate in the exhaust and combustion areas — wet stacking — visible as black oily residue at the exhaust and a drop in performance. Over time it fouls injectors, valves, and the turbo. Lightly-loaded standby units are especially prone to it.

The fix and prevention: load

Running the generator at a meaningful load (a healthy percentage of its rating) gets it hot enough to burn cleanly and burn off light wet-stacking buildup. This is why loaded exercise matters and why a no-load weekly run isn’t enough.

Load-bank testing

A load bank applies a controlled artificial load to the generator so it can be run at or near full rated output safely, even when the building doesn’t need that much power. A load-bank test:

• Proves capacity — confirms the unit can actually produce rated power under sustained load.
• Burns off wet stacking — runs it hot to clear accumulated buildup.
• Surfaces weak spots — cooling, fuel delivery, and exhaust problems that only appear under real load.

Many facilities load-bank test annually (and it’s required or recommended for certain critical/standby installations). It’s the difference between hoping the generator works and knowing it does.

Don’t forget the basics around it

Loaded exercise and load-banking sit on top of normal service: oil and filters, coolant, batteries (the top cause of no-starts), and fuel quality — stored diesel degrades and grows water and microbial growth, especially in Lowcountry humidity. Keep the tank healthy.

Make readiness provable

For backup power you’re counting on — a facility, a medical site, a critical operation — a documented schedule of loaded exercise and annual load-bank testing is how you prove readiness instead of assuming it.

Our shop can set up and perform generator service, loaded exercise, and load-bank testing so your standby power is ready when the grid isn’t.