If it fails: the first hour
What the site contact should do before the technician arrives.
- Check the control panel for a displayed fault code before assuming total failure
- Confirm the fuel level and that the transfer switch is in automatic mode
- Note which loads are affected if the generator is running but not carrying the full building
- Call the provider with the fault code or symptom and confirm whether the utility outage is still active
What fails
What a service call includes
- Battery testing and load capacity check, with replacement if below acceptable threshold
- Fuel quality testing and filter inspection, with fuel polishing recommendation if degradation is found
- Automatic transfer switch inspection and function test
- Coolant, belt and hose inspection with fluid levels checked and topped off
- Load bank testing to verify the generator can actually carry building load, not just run unloaded
- Control panel diagnostic check and sensor calibration verification
- Exhaust and air intake inspection for obstruction
- Written report documenting all test results and any deficiencies found
Preventive checklist
The items a maintenance program should carry for this system. Build a combined checklist across systems with the checklist builder.
Spring
- Full load bank test ahead of storm season
- Check exhaust and intake areas for winter debris or nesting before spring runoff
Fall
- Fuel quality test and filter change before winter demand increases
- Battery load test before cold weather reduces starting capacity
Quarterly
- Weekly or monthly automated exercise cycle verification, confirming the unit actually starts and runs on schedule
- Visual inspection of fluid levels and belt condition
Annual
- Full service including oil and filter change, coolant system service, and full load bank test
- Transfer switch full function test under simulated outage conditions
- Review generator capacity against current building electrical load
What it costs
| item | typical range | what moves it |
|---|---|---|
| Standard maintenance visit | $300 to $800 | Generator size and whether load bank testing is included |
| Annual maintenance contract | $800 to $2,500 per year | Number of visits included and generator kW rating |
| Load bank testing, standalone | $500 to $1,800 | Generator size, larger units require proportionally larger load banks |
| Battery replacement | $200 to $600 | Battery type and quantity for the starting system |
| Fuel polishing service | $400 to $1,200 | Tank size and degree of fuel degradation |
National ranges. Local labor, access, after-hours timing and materials move them. Multi-site programs usually price below one-off calls.
When this is an emergency
A generator that fails to start during an actual power outage, or shuts down mid-run while critical equipment depends on it.
How to choose a provider
- Ask whether load bank testing is included in the standard maintenance program or offered only as an add-on
- Confirm the provider services the specific transfer switch brand and type installed, not just the generator engine
- Ask how weekly or monthly exercise cycles are verified, remote monitoring versus manual log review
- Check response time commitments for a generator failure during an active outage
- Ask about fuel testing frequency for diesel units, since fuel degradation is a common and preventable failure point
Questions
How often should a standby generator be tested under load?
A full load bank test at least annually is standard, in addition to the shorter automated exercise cycles that run weekly or monthly without a real building load applied.
Why would a generator run fine during a test but fail during an actual outage?
Most exercise cycles run the generator unloaded or lightly loaded, which does not reveal whether it can actually carry the building's full electrical load for an extended period, only a load bank test does that.
How long does diesel fuel last in a standby generator tank?
Typically 12 to 24 months before degradation becomes a concern, depending on tank conditions and whether a fuel treatment or polishing program is in place.
What is the role of the automatic transfer switch?
It senses a utility power loss and switches the building's electrical load to the generator automatically, then switches back once utility power is restored, and its failure means the generator running correctly still does not help the building.