How long does a whole-house generator last?
Updated August 2026
A standby whole-house generator lasts 20 to 30 years, or about 3,000 running hours, whichever comes first. Run time matters more than the calendar here: during a multi-day outage the unit can log 24 hours a day, so a home in a storm-prone area burns through those hours faster than one that only fires up for a weekly self-test. Air-cooled models sit at the shorter end of the range, while larger liquid-cooled units reach the top. Skipping the yearly service is what turns a 25-year machine into a 12-year one. Installed, expect $4,000–12,000.
Lifespan by type and situation
| Type or situation | Typical lifespan | Why |
|---|---|---|
| Air-cooled standby | 20–25 years | Most residential units, in the 7–22 kW range |
| Liquid-cooled standby | 25–30 years | Larger 22 kW and up, heavier duty and cooler running |
| Measured in run hours | About 3,000 hours | Whichever comes first; long outages spend them fast |
| Serviced every year | Top of range | Oil, filters, and a load test keep it there |
| Never serviced | Cut 5–10 years | Old oil and clogged filters wear the engine early |
| Frequent multi-day outages | Hours spent faster | A storm-belt home may hit 3,000 hours in 15–20 years |
| Portable generator, for contrast | 1,000–2,000 hours | A different animal, not a permanent whole-house fix |
Signs yours is near the end
- It cranks longer than usual before catching, or fails a weekly self-test
- Rising oil consumption and darker exhaust, signs of a tired engine
- A run-hour meter approaching or past 3,000
- Rust on the enclosure or corrosion on the transfer-switch contacts
- Rough running, surging voltage, or lights that flicker on generator power
- Repair bills for the controller or alternator on a unit already past 20 years
How to add years
A standby generator is an engine, and engines live or die on maintenance. A yearly professional service, plus an oil and filter change every 100 to 200 run hours or once a season, is what separates a 30-year unit from one that seizes at 12. Let the weekly self-test exercise cycle run so the battery stays charged and the oil circulates, and keep the enclosure clear of leaves and snow. Work the full standby generator checklist each spring, and after any outage longer than a day, check the oil before the next storm.
What it costs to replace: plan on $4,000–12,000 installed (air-cooled units toward the low end, large liquid-cooled toward the high). Replacing on your own schedule, before it fails, is almost always cheaper than the emergency version. The home maintenance cost calculator helps you set the money aside before it comes due.
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Track your home's systems, free for 30 daysFrequently asked questions
How many hours does a whole-house generator last?
Around 3,000 running hours for a residential standby unit, which is more everyday runtime than it sounds. A weekly 12-minute self-test adds only about 10 hours a year, so test cycles alone would take centuries to use it up. The hours get spent during real outages, when the generator can run 24/7 for days. In a region that loses power for a week each year, you might burn 150 to 200 hours annually and reach the 3,000-hour mark in 15 to 20 years rather than 30.
Does a standby generator need maintenance if it hardly ever runs?
Yes, and idle units fail as often as busy ones. Oil degrades on a calendar, not just from use, so it needs changing at least once a year even if the run-hour meter barely moved. The starting battery is the number-one cause of a no-start during an outage and lasts only 3 to 5 years. The weekly exercise cycle exists for exactly this reason: to circulate oil, keep seals from drying out, and confirm the unit will actually start when you need it.
Is it worth repairing an old standby generator?
It depends on the part and the hours. A new battery, spark plugs, or a control board on an otherwise healthy 12-year unit is easy money. But a failed alternator or an engine rebuild on a generator past 20 years, or near its 3,000-hour ceiling, often costs half of a new unit, at which point replacement wins. Because a fresh install runs $4,000–12,000, price the repair against that number and factor in the warranty and efficiency a modern unit brings.
How often should you service a whole-house generator?
Once a year at minimum, ideally before storm season, plus an oil-and-filter change every 100 to 200 run hours. A yearly service covers the oil, air and fuel filters, spark plugs, battery, valve clearances, and a full test under load. Most owners buy an annual plan from the installer for $200 to 400. Between visits, glance at it monthly for leaks, corrosion, and error codes on the controller, and never disable the weekly self-test that keeps everything limber.