How Long Can A Generator Run Continuously?

Most portable gasoline generators are designed to run about 8 to 12 hours continuously (at half load) on a single tank. 

Now, if you have a propane generator, you can run up to 200 hours with an unlimited supply of propane tanks!

That’s about eight days, worth of continuous power before you have to change the engine oil.

In this article, I will answer the common question that you might be asking yourself – how long can a generator run continuously?

Bear in mind that every generator is different. The engine size, fuel tank size, ambient, maintenance, and loads can affect a generator’s runtime.

Let’s dive in!

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How Long Can A Portable Generator Run On Gasoline?

Typically, a portable generator run on gasoline can run about 9 to 12 hours continuously. Well, these numbers are calculated when the generators run at half load.

The more load you put on it, the more power a generator produces, the more gasoline it’s consumed. Thus, a shorter runtime.

Seldom can a gasoline generator run more than that simply because the fuel tank size limits it. Once the gas is running out, you have to refuel again.

WARNING: Gasoline and gas fumes are highly flammable. Do not fill the tank near an open flame. Do not overfill. Always check for fuel spills.

But before you refuel it, please allow the generator to cool down because of the hot tank. Besides, if your genny has been running for a certain period, you might want to change the engine oil.

A small 2000 Watts gasoline generator can run about 8 to 9 hours at half load because it has a smaller engine size and the loads it can handle are usually low.

For instance, a 4000 to 5500 Watts generator typically can run about 11 to 13 hours at half load. 

To give you some ideas, here’s the comparison for the smaller gasoline generator to the larger gasoline generators:

Conventional Generators

Inverter Generators

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How Long Will A Generator Run On Propane?

If you’re running a portable generator on 20 lbs BBQ propane, it’s estimated to last about 8 to 12 hours, depending on load and ambient temperature [1].

Unlike a gasoline generator, a propane generator (and dual fuel generators) can run continuously for many hours – assuming you have an infinite supply of propane.

Technically, you can keep your generator running without having to stop to refuel. What I mean by this is that you can connect two propane tanks in series.

Using a propane gas regulator like this allows you to remove an empty cylinder for refill without interrupting the propane supply.

BUT! There’s a limitation. Your propane generator requires maintenance after some time. Typically, about 100 hours of runtime.

The engine oil can be decreased and degraded over time and need to be changed. 

To give you some ideas on how long a propane generator can run, here’s the comparison of three popular propane generators in the market:

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How Long Can A Diesel Portable Generator Run?

A portable diesel generator is kind of different from the other generators. Most other generators in the market are gas-powered or propane, or dual fuel generators.

It’s because diesel generators are very famously noisy. However, a diesel portable generator has a longer runtime than other types of generators.

For instance, a 5000W Diesel Generator by Generac can run about 32.4 hours at half load on 12 gallons of diesel.

Some of the portable diesel generators can achieve more than 10 hours of runtime on a smaller fuel tank.

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How Long Can A Standby Generator Run?

A standby generator is probably the best backup power for your home. Generally, they have a longer runtime than portable generators.

But bear in mind that most manufacturers recommend that you limit your generator to 500 hours of use at the most. 

That’s about three weeks of continuous use. It might be a good idea to shut the generator down for purposes of engine cooling periodically.

There are three types of fuel used for a home standby generator. 

Let’s take a look at each one:

Natural Gas Standby Generator

Natural Gas Standby Generator is one of the most popular types of home backup generators because it will run indefinitely as long the natural gas (NG) is supplied to the generator.   

There is no need for a fuel tank since there is an endless supply of NG from your utility company.

On average, an NG standby generator can run about 100 to 165 ft3/hr (cubic feet per hour) at the half load, depending on the size of the power output.

Below is the comparison of some of the popular natural gas standby generators:

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Liquid Propane Gas Standby Generator

If your standby generator is fueled by liquid propane (LP), a fuel tank and generator run time will 

be limited by the amount of fuel remaining in the tank.

Nowadays, many standby generators can run on dual fuels – liquid propane (LP) and natural gas (NG). 

Based on the same standby generators mentioned above, the average runtime that a liquid propane gas standby generator can run is about 90 to 180 ft3/hr (cubic feet per hour) at the half load.

Here’s the comparison:

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Diesel Standby Generator

Similar to the LP standby generator, a diesel standby generator also has a fuel tank. Every diesel generator is different.

On average, one full tank of the diesel standby generator can last for at least 48 hours non-stop, whereas some are designed for 72 hours or more. 

Here is the example of runtime two diesel generators by Generac:

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Conclusion

You can run your generator as long as the fuel supply is enough, but it’s not strictly necessary to run your generator continuously.

Every generator, whether it’s portable or standby generators need to perform some essential maintenance. Like changing engine oil.

Please allow the engine to cool down after running for an extended period. Don’t abuse your generator.

Give some love to your genny!