How Long Does A Generator Last? (2024 Run Time Hours)

Most homeowners have had to run a generator to power their home before, but how long should you continuously run that generator for? Keep reading to find out!

In this guide, you will learn:

  • How maximum runtime for a generator!
  • Things that affect runtime
  • Different fuel options  
  • And more!
how long does generator last

Having a generator around is definitely not a bad thing! Having a portable one allows you to be able to use it for more than just backup power at your home, you can also use it for camping.  Having a standby generator makes it so you barely even notice the power went out!  

As a homeowner and electrician, I highly recommend getting one that would suit your needs, instead of sitting in the dark and letting freezers thaw. 

Keep reading to learn more about running generators continuously!

How Long Can Generators Run?

If you are using a standby generator, the average run time is about 2,500 hours though it is recommended to not run it continuously for more than a few hundred hours without cool down periods and maintenance checks.  

When using a portable generator, it can run continuously anywhere from 8 hours to 200 hours.  

Every generator is different and can have different run times based on fuel type, tank size and purpose. 

There are two types of generators: standby and portable generators.  Both are designed to keep your house powered up but not all are designed to run for days on end!

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Standby Generators Runtime

Standby generators are the best option for long term power outages.  These typically are wired into the house and are set up to automatically transfer power to run off the generator or have a manual transfer switch. They are also sized to be able to power your entire home. 

These can be fueled by either natural gas, diesel, or propane.  They can have large storage tanks for the fuel or be directly piped into the main fuel lines that feed your house. Making them capable of having a long runtime.

This type of generator can have a lifetime of up to 2,500 hours, so depending on how often and how long you use it could last for years with the proper maintenance!

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Portable Generators Runtime

Portable generators are more common for shorter runtimes and are useful for temporary power.  Many people will use them for camping along with backup power for their home during an outage.  These generators are not set up for automatic transfer and are not normally sized for running an entire house but rather some main appliances and lights. 

They can be fueled by gasoline, diesel, or propane.  Depending on fuel tank size they typically are only capable of running for 6-18 hours continuously. 

With proper maintenance a portable generator can have a lifespan of 1,000 to 2,000 hours.   

how long can generators run

Factors That Can Affect Generator Run Time

What fuel type can dictate how long your generator is able to run continuously due to the capacity of the fuel tank.  Below we will discuss each fuel type. 

The size load you have on your generator will also affect the length of time your generator is capable of running for due to fuel usage.  If you only run it at half load, it will use less fuel and be able to run longer.

The load size can also affect the length of time the generator is able to run because of the amount of heat created. If it is being run at full capacity, you will not be able to run it quite as long as you would at half capacity.  Running the generator for too long of a duration can cause heat buildup and can cause permanent damage!

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How Long Generators Last Depends On Fuel Type

The type of fuel used in a generator can make a substantial difference to the runtime. For more information, we recommend reading A Comparison of Fuel Choice For Backup Generators from

Portable Gasoline Generator Runtime

A portable gas generator may have the shortest run time, mainly because it must be shut down to be refueled.  It is recommended to let the generator sit for 5-10 minutes before refueling. This is for safety reasons, gasoline spilt on a hot engine can create a fire hazard.

Gasoline has a shelf life of 6 months, so it is hard to store large amounts.  Although, it is also one of the most readily available fuel types. 

These generators have an average run time of 6-12 hours depending on how big the fuel tank is along with the load that it is running. 

Portable and Standby Propane Generator Runtime

A portable or standby propane generator can have a run time that directly correlates to the size of the fuel tank it is hooked up to. It is possible to extend the continuous runtime of a portable propane generator by connecting two tanks to the fuel line using a changeover regulator. This allows you to remove one tank without having to shut down the generator. 

Since propane has an indefinite shelf life you can have a large storage tank or even multiple waiting to be used. 

There is a wide range of tank sizes so you can run them continuously from 5 hours all the way up to 200 hours. While it is possible to run up to 200 hours you may have to do regular maintenance, like checking the oil on it, roughly every 100 hours. 

Portable and Standby Diesel Generator Runtime

Much like a gasoline generator, a diesel portable generator can run on average of 6-12 hours depending on its fuel tank size. A standby diesel generator is capable of running for up to 500 hours at maximum capacity as long as you have unlimited fuel supply or a large storage tank.

While it has a little bit longer shelf life compared to gasoline, it should be used within two years. Diesel is typically readily available but is usually more pricey than other fuel options.  

Due to the low maintenance of a diesel generator, it is capable of running 2,000 to 3,000 hours before it needs service.

You may also be interested in this calculator from on diesel generator runtimes.

Standby Natural Gas Generator Runtime

Natural Gas standby generator can be tied into the main line that feeds your home. Tying into the main line ensures that you never run out of fuel but in a disaster situation, such as a hurricane or tornado, the main gas line may be shut off leaving you with no fuel. 

A natural gas generator can run as long as there is no interruption in the fuel supply. You should check the service manual to see what it recommends on run time says before it needs to be shut down for service. 

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What to Consider When Buying Generators

Before you buy a generator, you should consider if you want to be able to use it other than at home.  If you do, go for a portable generator.  You can use it for emergency power or even camping.  

If all you want is backup power at home, then a standby generator might be the way to go.  This can ensure seamless transition between main power and backup power. 

Whichever one you pick make sure the wattage rating is sized to run the load you need to! 

Frequently Asked Questions On Generator Hours

Can You Run A Generator 24 Hours A Day

Yes, you can run a generator 24 hours a day depending on the size of your fuel tank. 

Is It Okay To Leave A Generator Running All Night?

As long as it is fueled up and outside where carbon monoxide will not be an issue, yes you can run a generator all night.  

Can A Generator Run For A Week? 

Yes, you can run a generator for a week, but it is not recommended to run it continuously.  Daily it should be shut down for a cool off period and check all fluid levels. 

How Long Should A Generator Be Run In A Day?

A generator can run as long as its fuel supply lasts. Check in the owner's manual to verify runtime lengths and when maintenance should be done.

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Final Thoughts

Portable generator runtime can be limited to the capacity of their fuel tanks but can be useful in more than just power outages.  Standby generators can make the transition between main power and backup power almost seamless. Each one has its own benefits.  You just have to decide which one is best for you.  

No matter what having any form of backup power is better than having none at all! 

I hope you enjoyed this Home Inspector Secrets guide!

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