If you're a contractor, facility manager or event coordinator, you may question whether a used generator will hold up when you need it most. The short answer is yes, when you know what to look for. Understanding runtime, maintenance and reliability takes the guesswork out of the decision and puts dependable power within reach at a fraction of the cost of buying new.
What Does Runtime Mean on a Generator?
Runtime is the total number of hours the generator engine has been actively running since the machine was built or last rebuilt. Industrial diesel generators are engineered for 15,000 to 30,000-plus operating hours. A unit with fewer than 5,000 hours is considered low use with significant life remaining. The frequency of use also matters. A standby unit that runs only during power outages and monthly tests wears far less than one that operates daily on a jobsite, even if the hour counts look similar. Hours tell part of the story. Maintenance history reveals the rest.How to Maintain a Used Generator
Timely service is essential to keep a generator running well. Properly maintaining a generator encompasses fluid management, filter replacements and load bank testing. Change the oil every 250 hours on prime power units and every 500 hours on standby units, or as recommended by the manufacturer. Swap air and fuel filters before they restrict airflow or contaminate fuel delivery.How Long Should You Run Your Used Generator for Maintenance?
Load bank testing runs the generator at full rated capacity, burns off carbon buildup from light-load use and proves the unit will deliver when it counts. A 30-minute monthly run is the baseline minimum. It's important to exercise your diesel generators at 30% or more of nameplate capacity.Used Generator Red Flags
Knowing how to ensure used generator reliability starts with understanding what to avoid. Before committing to any unit, watch for:- Excessive rust or corrosion on the engine block, housing or fuel tank.
- No service records or maintenance documentation.
- Inconsistent or unverifiable runtime hours.
- Visible oil or coolant leaks around the engine or fittings.
- No load bank test results on file.
