Generator Maintenance Schedule

Generators are unusual machines: they sit idle for months, then must start immediately and run for days. Nothing else in a house is asked to do that.

Maintenance is what makes it work, and one habit matters more than all the others.

Maintenance intervals

Two lines matter more than the rest. Stale gasoline is the number one reason a portable won't start — stabiliser or drain it. And a dead battery is the number one reason a standby fails to start when it is finally needed, which is precisely why they self-exercise.

How often should you run a generator?

15 to 30 minutes, under load. Not idling — connect something real, like a space heater or a few work lights.

Why it works:

• Circulates fuel, so the carburetor doesn't sit dry or varnishing
• Circulates oil, coating internal surfaces
• Conditions seals and gaskets, which dry out unused
• Charges the battery on electric-start units
• Reveals problems while you have time and daylight

This single habit prevents most of the failures in generator won't start: troubleshooting.

Standby generators do this automatically — see generator exercise mode. Portables need you to do it.

Every use

• Check oil before starting. Low oil triggers the shutdown, and running low destroys engines.
• Check fuel level and condition.
• Look it over — loose fasteners, damaged cords, debris in the cooling intakes.
• Clear the area — 20+ feet from the building, exhaust directed away, nothing enclosing it. See generator carbon monoxide safety.

After each extended run

• Let it cool before refuelling. Never refuel a hot or running generator.
• Check oil again if it ran many hours.
• Wipe it down and store it dry.

What annual generator maintenance is needed?

Oil and filter change. Manufacturers typically specify an initial break-in change after the first few hours, then every 50–200 running hours or annually. Check your manual — this varies by engine. See generator oil change.

Air filter. Clean or replace. Foam elements are often washable; paper ones are replaced.

Spark plug. Inspect, clean or replace, and check the gap against the manual.

Fuel filter, where fitted.

Spark arrestor, on units that have one. Cleaning it is required in many jurisdictions for use on public land, and it affects performance.

Valve clearance, on some engines at longer intervals. Manual territory.

Battery, on electric-start units. Test it, clean the terminals, and consider a maintainer if the unit sits.

How do you prepare a generator for storm season?

Do this on a calendar date, not when a forecast appears:

• Test-start under load — 20–30 minutes
• Oil at level, changed if due
• Fresh, stabilized fuel — or full propane tanks
• Spare oil, filters, and spark plug on hand
• Cords inspected — no damage, correct gauge for the length
• Inlet box and interlock checked, and everyone who might operate it knows how
• CO alarms tested, batteries fresh, within service life
• Placement planned — where it goes, where the exhaust points

The last two are the ones that matter most when things go wrong.

Standby generators

More demanding, because the whole proposition is unattended starting.

Weekly: the automatic exercise cycle runs itself. Check that it actually happened — most controllers log it.

Monthly: visual check, look for fault codes or warning indicators, confirm the enclosure is clear of debris and vegetation.

Annually: professional service — oil and filter, air filter, spark plugs, valve adjustment where required, battery test, transfer switch inspection, and a load test.

The battery is the most common failure. It sits on a trickle charge for years, and it degrades. A standby generator that fails during an outage very often has a dead battery.

Manufacturers usually require documented maintenance for warranty coverage. Keep the invoices.

How do you store a generator long term?

Two valid approaches:

Run it dry. Shut the fuel valve and let it run until it stops, so no fuel remains in the carburetor to varnish. Best for storage beyond a few months.

Store full with stabilizer. Less air space for condensation, and stabilized fuel keeps. Requires running it periodically so treated fuel circulates.

Either way: change the oil before storage, remove the spark plug and add a small amount of oil to the cylinder on some engines (check the manual), and store it covered, dry, and off the ground.

See gasoline storage and stabilizer.

Keeping records

A simple log — date, hours, what was done — pays for itself twice: it tells you when service is due, and it's the documentation a warranty claim needs.

Note running hours if the unit has an hour meter. Interval-based maintenance is meaningless without it.

Where to go next

• Generator won't start: troubleshooting
• Generator oil change
• Generator exercise mode
• Size it properly: generator sizing calculator

More in our generator and backup power guides.