Generators are a mainstay with many homesteaders, off-grid dwellers, or people wanting to be prepared for power outages. When planning for emergency use, it is important to know how long your generator can run continuously.

After all, power outages can last for a while.

Most portable gasoline generators are expected to run for up to 8 to 12 hours.  The exact length of time a generator can run depends on generator size, fuel type and power load.  The temperature of the generator and oil level can also affect how long a generator can run continuously.

Want to figure out how to calculate your specific generator’s runtime? Do you need to know the difference between gas, propane, and solar-powered generators? Keep reading to find the best generator for your electricity outage plan

Recommended Runtimes for Generators

How long your generator runs depends on what type of generator you’re using.  

Most gasoline generators can run 9-12 hours straight without refueling. Propane generators can run for 24 hours, others that can run for over 24 hours. The latter is used for entire home electricity backup and is expensive to buy and fuel.

The most important thing to remember is generators are meant for short periods. That means some larger ones can run for 24 continuous hours, but most cannot and should not.

To calculate how long your generator will run non-stop, divide the generator’s fuel capacity by its fuel consumption to estimate max run time.

How much fuel your generator will consume, and thus how long it can run for, depends on how much power you’re using. Many generators provide estimated run time on the product specs, based on you using half the available capacity of the generator.

It’s also worth noting that most generators’ life expectancy is based on hours of use rather than years. If you use your generator continuously over the few days of power outages, it won’t last as long as if you use it intermittently.

Do I Have To Shut Off A Generator To Refuel?

You should not refuel your gasoline generator while it’s running.  Gasoline is highly flammable, and the hotter your generator is, the more at risk you are. What that means in practice is that the gasoline fumes are highly combustible and can create a massive fire from a single spark.

Turn your generator completely off and wait 5-10 minutes for it to cool down before filling it up with more fuel.

If you simply must run your generator for long periods of time and do not want to go thru the hassle of having to refill the tank for any reason, you could extend the size of your generators gas tank by hooking it up to an external gas tank.  To do this you need to purchase this kit.

One end hooks up to your generatorʻs gas cap and the other to a utility gas can.  As long as the generator starts off with gas in itʻs own tank, the external tank can be refilled while the generator is running.

Gas Generator vs. Propane Generator vs. Solar Generator

You do have choices when it comes to finding a generator that runs continuously. Since you’re limited by how fast your generator burns fuel, it’s worth exploring generators that run on different sources.

Gas Generators

Gas generators must be shut off when their fuel runs out. That means your run-time is limited by the size of the gas tank and the time it takes your generator to run through it. Once you do cool off your generator for a few minutes and refuel, you can keep using it, though.


  • Efficient and easy to purchase gas
  • Burns in cold weather


  • Causes build-up in generator’s engine
  • Must use fuel stabilizer to store gas
  • Highly flammable

Propane Generators

Propane tanks are simple to change when one becomes empty. If you hook up two propane tanks to a single gas line, you can theoretically have power until your generator runs out of oil in around 150 hours. That does not mean you should run a propane generator for that long.

Your generator will pick excess heat if run nonstop. If you don’t give it a break every 12-24 hours, you can cause permanent damage to the engine. This is especially true if the weather is hot and if you’re running the generator at higher wattages.


  • Propane generators are quieter
  • Cylinder containers don’t spill and are easy and safe to store
  • Propane lasts for a long time without stabilizers


  • Not as fuel-efficient as gas
  • Propane engines are complex and difficult to fix
  • Propane is not very efficient

Solar Generators

Your solar generator’s run time is limited by how much energy it can store in the battery if you run it at night or during low sunlight. If it’s a large battery, it’ll have a longer run time than a smaller battery. When you run out of power, it can take up to 9 hours to repower your generator.


  • No fuel costs.
  • Uses clean, renewable energy
  • Quiet


  • Slow recharging
  • Limited power supply
  • Expensive to buy

Related: What Size Generator Do I Need To Be Off Grid?

Why I would get a Dual Fuel Generator

A dual fuel generator can run on either gas or propane. That means you can use the cheaper, more fuel-efficient gas when gas is available, but you have options if a disaster strikes. 

Suppose electricity is out for long periods (gas stations are powered by electricity) or your gas station runs out of gas. In that case, you can flip the switch on your generator and start using propane that might still be available at gas stations and lasts in storage for years.

There are conversion kits available that can help you convert your portable gas generator to a propane one. The problem with these kits is they usually aren’t made by the manufacturer and void the warranty if you use them.

The best bet is to purchase a dual fuel generator for peace of mind. Ultimately you’re buying a generator to have backup electricity no matter what the situation is. Dual fuel generators give you that. You can even look into tri-fuel models that can run on gas, natural gas, or propane.


There are many generators available on the market. The most common, the portable gas generator is efficient and can run continuously for 8-12 hours. 

If you’re prepping for long-haul outages where you’ll be reliant on your generator, your best bet is to purchase a dual fuel generator or a larger propane generator. Propane stores safely for years and is less likely to be bought up in an emergency than gasoline. 

Even if you purchase a propane or dual fuel generator, remember most of these models are not designed to be run continuously for days on end.

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