Backup Generators · Service

The machine has one job, on one night

A standby generator spends years doing nothing and is then asked to be perfect. Maintenance is the entire difference between owning one and having one — and the part that fails first is almost never the engine.

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In short

What is generator maintenance?

Generator maintenance is a scheduled service on an engine that hardly ever runs: oil and filters, spark plugs, the air intake, the battery and charging system, the fuel supply, the enclosure, and a live test through the transfer switch. It follows the manufacturer's stated schedule, which counts both elapsed time and running hours — so a machine that idled through a quiet year is still due. The item that most often stops a standby generator starting is the battery, not the engine.

Triggers

Signs you need generator maintenance

You have a standby generator and cannot remember the last time anyone serviced it
The weekly exercise cycle has stopped happening, or you have never actually heard it run
A warning light or a fault code is showing on the controller and the machine is otherwise sitting quietly
It ran roughly during the last outage, or dropped the load when something large started
You inherited the generator with the house and have no service history for it
Storm season is approaching and you want to know the machine works before you need it to

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The job

How generator maintenance actually works

Read the controller and the run history first

A competent visit starts at the controller, not with a spanner. Modern units log run hours, exercise cycles, faults and start attempts, and that history tells the technician what to look at — a machine that has been silently failing its weekly self-test for months is a different job from one that has been running cleanly.

Watch for: A technician who goes straight to the oil without looking at the log. The history is the diagnosis, and it is free.
Test the battery and the charging system properly

This is the highest-value part of the visit. A standby generator sits with its battery on a maintenance charger for months on end, and the failure mode is a battery that reads a healthy voltage at rest and collapses the moment the starter draws on it. It needs a load test, and the charger itself needs checking, because a failed charger kills batteries quietly.

Watch for: A battery checked with a voltmeter alone and declared fine. Resting voltage tells you almost nothing about whether it can turn an engine on a cold night.
Oil, filters, plugs and the air intake, to the manufacturer schedule

The consumables, changed on the interval the manufacturer states for that machine — which is defined by both time and running hours, whichever comes first. Air intakes matter more than people expect on an outdoor machine, because they collect grass clippings, leaves, dust and insect nests over a year of sitting still.

Watch for: A service done to a generic annual checklist rather than to the machine's own schedule. Different units and different fuels have genuinely different requirements, and the manual is the authority.
Check the fuel supply under load, not at rest

On a natural gas machine that means confirming supply pressure while the generator is running and loaded, since a marginal supply looks perfectly fine at idle. On propane it means the tank level, the regulator and the lines. Fuel supply problems are invisible until the machine is asked to work.

Watch for: A pressure reading taken with the machine idle. It is the single most common way a genuine supply problem passes a service visit.
Run a real transfer test and confirm the exercise schedule

The visit should end with the machine starting, taking real load through the transfer switch, and returning to utility power — the same sequence it will perform in an outage. Then the exercise schedule is confirmed as set and running, at a time that suits you rather than at seven on a Sunday morning.

Watch for: A test run with no load transfer. An engine that starts and runs unloaded has proved one third of the system.

Money

What does generator maintenance cost?

An annual service visit is typically a few hundred dollars, with multi-year or twice-yearly plans priced above that and parts sometimes billed separately. Battery replacement is the recurring extra. Budget for it as a running cost of ownership. See the generator cost guide for ranges.

See the full generator maintenance cost guide — by material, size and region →

Straight answer

When generator maintenance is the wrong call

Everyone else ranking for this is paid when you say yes. Here's when you shouldn't.

You have a portable generator, not a standby unit. Portables do not need a service contract — they need you to start them every few months, keep the fuel fresh and change the oil. Paying a contract price for a machine you can maintain in twenty minutes is not a good trade.
The plan is priced like a service but excludes parts, travel and call-outs. Read what is actually included. A cheap headline plan that bills separately for the filters, the battery, the mileage and any visit outside the annual one can cost more than paying per visit.
You are inside a warranty that already requires dealer servicing. Check the terms before buying a plan from a third party — some warranties specify who may service the machine and what records are needed, and a cheaper plan can quietly forfeit the cover.
The machine has a real fault right now. A maintenance visit is not a repair. If it will not start, is throwing a fault code, or dropped the load during the last outage, get it diagnosed and fixed first, and start the maintenance plan afterwards.
The plan does not include a load transfer test. That is the test the whole thing exists for. A contract covering oil and filters but never proving the machine will carry your house is checking the easy things.
You are about to sell the house. Buy the single visit and get the written report — a documented service history is worth more at sale than the remainder of a plan the buyer cannot easily take over.

Before you sign

What to check when hiring for generator maintenance

Do you service this make, and can you get parts for it?

Parts availability and controller access vary by brand, and a technician who cannot read your controller or source a board is limited to the easy work.
Does the visit include a load transfer test?

The one test that proves the system rather than the engine. If it is not in the scope, the visit is not verifying what you actually bought the generator for.
Will you load-test the battery, not just measure it?

The most likely single point of failure in the whole machine, and the one most commonly waved through on a voltmeter reading.
Are parts, travel and emergency call-outs included, or billed on top?

Where the real cost difference between plans lives. Get it itemised rather than comparing headline annual prices.
What is your response time during a regional outage?

The honest answer is usually "we will be busy". Better to know the queue position you are buying than to assume priority you do not have.
Will I get a written report with readings on it?

It is your service history, it matters at resale, and some warranties require documented maintenance. An invoice signature is not a record.
What is your recommended interval for my specific machine and how did you determine it?

It should come from the manufacturer's schedule for that model and fuel, counting both time and running hours — not from a standard annual package applied to everything.

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Local pros

Generator Maintenance near you

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Related work

Often done at the same time

Generator Repair

When it will not start or drops the load

Whole Home Generator Installation

Buying one

Generator Transfer Switch Installation

The part the load test proves

Natural Gas Generator Installation

Fuel supply checks

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FAQ

Generator Maintenance — questions people ask

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How often does a standby generator need servicing?

To the schedule the manufacturer sets for that specific machine, which is defined by both elapsed time and accumulated running hours — whichever arrives first. The practical consequence people miss is that a quiet year with no outages does not defer anything: oil degrades, batteries age and rodents move in regardless of whether the engine ran. Machines that carried long outages need attention sooner, on the hours.

Why do standby generators fail to start when they are needed?

The battery, far more often than anything else. It sits for months at a time being trickle-charged, and the characteristic failure is one that reads a perfectly healthy voltage at rest and then collapses when the starter draws current on a cold night. After that come stale or contaminated fuel on liquid-fuelled machines, a gas supply that is marginal under load, rodent damage to wiring inside the enclosure, and a low-oil shutdown on a machine nobody has checked.

What is the exercise cycle and does it matter?

It is a scheduled self-test where the controller starts the machine and runs it for a short period on its own, usually weekly or fortnightly depending on the setting. It matters a great deal: it circulates oil, keeps seals from drying out, keeps the battery charged through the charging system, and — most usefully — surfaces a problem while it is still an inconvenience. If yours is not running, something is wrong, and that is worth investigating before the next storm.

Is a generator maintenance plan worth it?

For a permanently installed standby unit, generally yes — mainly because it converts a task you will forget into a visit that happens, and forgetting is the dominant failure mode with these machines. What decides value is the detail: whether parts, travel and call-outs are included, whether a load transfer test is in the scope, and what response time you actually get in a regional outage. Compare those, not the headline annual price.

What happens if I never service it?

It will very likely still be sitting there looking fine, and it will very likely not start on the night you need it. That is the specific cruelty of standby equipment: nothing about neglect is visible until the moment of use. The usual sequence is a battery that quietly dies, an exercise cycle that stops running with nobody noticing, and a first indication of a problem that arrives during the outage, in the dark, when every service company in the region already has a queue.