How Long Can You Run a Generator Continuously?

Generators can be used for everything from lighting up your camping trip to powering an outdoor party to keeping your home running during an emergency. While you might only need your generator for a few hours in most cases, prolonged power outages present a unique situation where you might need to run your generator for as long as it can go.

Which begs the question, how long can you run a generator continuously for before you run into trouble?

 The answer is more complicated than you might expect, since it depends on the type of generator you have and what type of fuel you’re using.  So, we’ll look at several different cases.

Portable Generator with Gasoline

If you’re running a portable generator on gasoline, the amount of time you can run your generator for will be the most limited.

The reason is that you should never refuel a gasoline generator while it’s running. Even though it seems tempting to simply pour more fuel into the tank, this is an extremely dangerous thing to do.

A running generator is hot, which presents a risk that fumes from the fuel you’re adding could spark and cause the generator or the gasoline tank that you’re holding to burst into flames unexpectedly.

The bottom line: turn off your generator and let it cool down whenever you’re refueling with gasoline.

That means that for gasoline, you’re limited to the rated runtime of your generator. Depending on your generator and how much power you are drawing, that may be anywhere from just a few hours to 12 or more hours. But, there are few portable gasoline generators with a fuel tank large enough to last for days. 

The Westinghouse WGen3600v can run for 18 hours per tank – which is on the longer end of those we recommend.

Portable Generator with Propane

If you have a generator that runs on propane, you are in control of the fuel tank. That offers some additional options for keeping your generator continuously fueled.

The simplest way to extend your runtime with a propane generator is to hook up two propane tanks to a single gas line via a stopcock valve – or changeover regulator. That way, you can turn on the flow from one propane tank and leave the other closed. When it comes time to switch propane tanks, you simply twist the stopcock valve.

In this scenario, you can actually replace the depleted propane tank with a fresh tank so that you never run out of fuel.

So, assuming that you have an endless supply of propane, how long can you run your generator for?

Most portable generators require maintenance every 100 hours, but this isn’t a hard-and-fast rule. Instead, what will truly limit you is the amount of oil in your generator’s engine. This typically runs low after 150-200 hours of use, and most modern generators will automatically shut off when the oil runs low in order to protect the engine.

Keep in mind that heat build-up is also an important consideration when running your generator far beyond its runtime. Generators may build up only a marginal amount of excess heat over a 12-24-hour period, but once you go beyond a day of continuous use you risk building up engine heat that could permanently damage your generator.

If you’re running your generator in warm weather, consider packing it with ice and using a fan to try to cool the engine down as much as possible. Also keep in mind that running the generator at higher wattages will generate more heat.

So, if you manage your generator properly, you could potentially run it continuously for as long as 150-200 hours on propane.

Standby Generators

If you need to run your generator continuously for more than a few days, a portable generator simply won’t cut it – you need a standby generator.

Standby generators have much larger and more efficient motors that are specifically designed to handle long-term use. They’re also designed to operate on natural gas lines or to connect to massive 500- or 1,000-gallon propane tanks.

Depending on your standby generator, most manufacturers recommend that you limit your generator to 500 hours of use at the most. That’s about three weeks of continuous use.

While you could potentially run your generator for longer, you will do so at the risk of permanently damaging your standby generator and any appliances plugged into it.

How Long Can You Run Your Generator?

So, if you have a portable gasoline generator, you’ll be limited to the runtime of a single fuel tank. This is usually more than a few hours, but far less than a full day.

If you are running a portable generator on a relatively unlimited supply of propane, you’ll be limited to the life of your engine oil. That gives you up to 200 hours, or about eight days, worth of continuous power.

Finally, if you are operating a standby generator with an unlimited fuel supply, you can run your generator for up to 500 hours – 21 days – at a time.

Keep in mind that whenever you are running your generator for extended periods, you need to monitor it. While generators are designed to provide backup power, they can only handle so much abuse and will eventually start to break down. If it’s not strictly necessary to run your generator continuously, it is best to turn it off, let the engine cool down, and perform basic maintenance before turning it on again.

6 thoughts on “How Long Can You Run a Generator Continuously?”

  1. I thought it was interesting when you explained that portable generators will require maintenance every 100 hours or so. My brother is thinking of purchasing a propane generator that he can use when his family goes camping. It seems like it would be a good idea for him to find a fuel company that he can get his propane supply from.

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  2. As far as i can remember .the spec for a portable generator .if the unit is a certified .by whatever standard applies in China.is a runtime of 4000 hours minimum but that is not continuous .8 hrs out of every 12 should be ok .

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  3. We ran ours post hurricane Laura for 3 weeks straight on gasoline using an external tank. We only shut it down for 5 minutes every 75hrs to change the oil and started it back up. It ran our camper a/c and all, fuel bill came in at roughly $1,700. This was nothing more than a big box store “Lowe’s” CAT brand 7500 watt generator. It currently has close to 750hrs on it, I’ve been shocked at the performance of this unit and plan to purchase another.

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  4. I purchased a Generac 22 KW standby natural gas generator. I have tested three times for around 6 hours equaling a total of 18 hours. When I looked at the display of total hours it shows 880 does this mean that the company sold me a used generator? According to the information above that’s almost 1/3 it’s lifespan so I don’t know what to do. The company that sold it to me and installed it has been notified.

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