How Long Does a Generator Last & Can It Run Overnight?

An unexpected power outage can happen at any time due to increased natural disasters causing line damage and grid failures.

Before 2013, power outages in the U.S. were only limited to 2 to 3 hours in a couple of months, but now it is more frequent and prolonged. It can even last for days if the nearby grid is damaged.

To counter power outages, a large number of people in the U.S. are purchasing portable and standby generators. According to Fortune Business Insights, the U.S. generator market rose to 4.68 Billion dollars and this number increased by the day.

But, the biggest question remains, how long does a generator last?

Typically, a portable gasoline generator can last for 6 to 12 hours depending on the fuel-tank size, but a standby generator run as long as it has the fuel. A big standby generator can run for 24 to 72 hours depending on the size of the fuel tank. Some Generac generators can even last for 168 hours before needing a refill.

How Long Can a Standby Generator Last in a Power Outage?

Ideally, a quality standby generator like a Generac can run as long as there is fuel in it. These big-ass whole-house generators are designed for emergency backup power to last as long as possible so runtime is not really an issue here.

Runtime is also affected by the fuel you are using. If your standby unit is on natural gas, fuel shouldn’t be of concern because the unit will be hooked to your home’s gas pipeline. You expect the generator to run as long as it doesn’t heat up. These generators are often designed for small commercial and residential purposes.

If you want to know more about generator runtime, read this research.

If you have a diesel standby generator, expect it to run for 24 to 72 hours depending on the fuel storage. Usually, large diesel generators are designed for big commercial buildings and industries. They can run as long as 300 to 500 hours with few breaks in between.

Recommended Read: Diesel vs gas generators.

What is the Average Lifespan of a Standby Generator?

The average lifespan of a mid-sized (12000 to 22000) standby generator is around 1500 – 2800 hours. These standby units are engineered in a way to withstand weather abuse, heat, and general wear and tear which is why their lifespan is very high compared to portable gasoline generators.

Even if your area doesn’t experience a lot of power outages, keep it checked by running it for a good 30 minutes a week.

How Can I Increase the Lifespan of My Standby Generator?

Standby generators are extremely durable requiring little maintenance compared to portable generators. Still, a machine is a machine unless it is ULTRON (Avengers reference).

I would suggest hiring a professional for a detailed maintenance checkup if you are got nothing to do with electronics and machines.

The professional will change the oil and check the wires, fuses, and other electronic components. He/she will also clean the generator for you.

If you can’t afford a professional, you should be able to:

  • Change the engine oil timely. The user manual will tell you when to change the oil for your particular model.
  • Rub off any dust from the body and make sure there is no accumulation of debris or dirt.  
  • Unclog the fuel pipe, and clean the carburetor if necessary.
  • If your generator runs at 3600 RPM, shut it off once every 8 to 10 hours to help it cool down a bit. It is not absolutely necessary, you can let it run for an entire day, but whenever you get a chance, make sure to give it a rest. Let the engine rest a bit.
  • If your business or home cannot afford to shut down even for a few minutes in case of a power outage, I would suggest getting an 1800 RPM generator. 1800 RPM units rarely get hot, they are very efficient and recommended for extended power outages.

When to Replace Your Standby Generator?

Although standby generators are an essential piece of investment that increases the stability of the home with great ROI, at some point, you would need to replace it with a newer one if it is giving you more trouble than you can handle.

The following factors are indications that your standby or portable generator is at its end and you need a replacement.

Frequent Repairs: Standby generators are built to last frequent and prolonged power outages without breaking down.

They don’t need repair much often. If your whole house unit needs more repairs than normal, and if it is also getting old, I would suggest replacing it with a newer one before it completely breaks down.

Generator Getting Old:

Generator Getting Old

Most quality standby generators are built to run for 1500 – 2800 hours. If you have already put miles on your standby unit, consider replacing it even if it is not 10 to 15 years old.

Fails to Start:

If the brand-new or semi-new portable or standby generator takes time to start or fails to start, I would suggest getting it replaced if the warranty is still intact.

I have seen these problems in many standby generators. It often takes long and expensive repairs to fix the starting mechanism.

With a portable generator, it is not that big of a deal because it is easy to open the frame and troubleshoot the problem, but a whole-house generator takes time and effort to locate the exact problem. Don’t hesitate to claim the warranty if it is not starting (Automatically or manually) as it should.

Which Factors Affect the Runtime of a Generator?

The following factors affect the runtime of a portable inverter generator and a whole-house generator.


It is pretty much straightforward, if your standby generator is rated at 12000 running watts and 15000 starting watts, and you are draining it to its peak capacity over and over again, it will surely reduce the lifespan of the machine.

Recommended Guide: How to Fix an overloaded generator?

Lack of Maintenance:

If you don’t change the oil on time, clean the fuel pipe, service the generator, and drain the carburetor (for gasoline), your machine will have a lesser lifespan.

Frequently Asked Questions (FAQs)

How Long Does a Generator Last?

Most standby generators last as long as 15 to 20 years. They may last even longer if you follow the manual’s guidelines, and schedule proper maintenance from time to time.

How Often Should You Replace a Standby Generator?

A standby generator remains operational for 10,000 to 30,000 hours of use. After that, it slowly begins to lose its reliability. So in theory, you should replace your standby generator after 15 to 20 years.

Is it Worth Fixing an Old Generator?

If your old generator is breaking down regularly and requires maintenance more than often, then you should consider replacing your old generator. It is not worth fixing a 15 to 20-year-old machine.

Can You Run a Generator Overnight?

You can run a generator overnight if the fuel tank is big enough. However, it depends on the type of generator and its specifications. Some standby generators can be run for extended periods and are designed to automatically turn on in case of power outages. In any case, don’t run the generator inside and the exhaust should be at least 30 feet away from the sleeping area to avoid CO poisoning.



Fareed, the highly skilled electrical expert, boasts 5 years of extensive experience in proficiently maintaining, repairing, diagnosing, and installing a diverse range of electrical systems.

Leave a Reply

Your email address will not be published. Required fields are marked *