Whole-house generator maintenance

A standby generator that sits untouched for a year is the one most likely to fail when the grid goes down. The maintenance it needs is light, but it’s not optional. Skipped service is the top reason a unit won’t start on demand.

The weekly exercise cycle

Most residential standby units run themselves for a few minutes on a weekly or biweekly schedule. That exercise keeps the engine limber, charges the starting battery, and lets the controller confirm the unit is healthy. You set the schedule at install and leave it on. If the unit misses an exercise cycle, that’s your early warning that something is wrong, usually the battery or the controller.

The exercise cycle is not a substitute for the annual service. It keeps the unit ready, it doesn’t replace oil or filters.

The annual service

Once a year, a standby unit wants:

• Oil and filter change. Air-cooled engines are the most common residential type and want fresh oil annually, or sooner if a long outage runs up the hours.
• Air filter check or replacement. A clogged filter costs output and run time.
• Spark plugs. Replaced on the manufacturer’s interval, often every other year.
• Battery inspection. The starting battery is the single most common cause of a no-start. It ages and should be replaced before it dies, not after.
• General inspection. Clearances, fuel line, transfer switch operation, and a load test.

This is work for an installer or a dealer, not a homeowner job on a fuel-fired, permitted system. Use the installer directory to find a local service, and check the dealer finder on the brand’s site when you compare standby generators.

During a long outage

A long run pushes you past the normal annual interval. If an outage runs the unit for hundreds of hours, you owe an oil change before the next outage, and possibly during it. The unit’s hour meter tells you where you are. NFPA 110 sets the service expectations for standby systems, and residential units follow the same pattern at a lighter duty cycle.

See the run-time guide for how fuel supply and service interact over a week-long outage.

Why units fail to start

In order of how often we see it:

1. A dead starting battery. It ages out in a few years and quietly dies. The exercise cycle would have shown it.
2. Stale fuel or a fuel supply issue. More common on propane with a low tank, rare on natural gas.
3. A tripped breaker or a controller fault. Often resets, but it means the unit didn’t run.
4. Skipped oil service. The engine protects itself by shutting down, which reads as a failure but is really neglect.

Most of these are caught by the annual service and the exercise cycle. A unit that’s serviced and exercised starts when you need it.

Plan for service before you buy

When you compare standby generators, check the warranty and the dealer network. A 10-year warranty with a strong local dealer is worth more than a 5-year warranty with no one to service it. See the installed cost with service in mind, because the buy price is not the whole cost.