How Long Can You Run A Generator Continuously? (2020 Guide)

by Johnathan Roos

Backup power generators are very common among industrial and office set ups. They have even become common household appliances. With that, a common question is how long can a generator run continuously.

After careful research and calculation, we have put together a simple guide for all your backup generator needs. Here, we will be breaking down the calculation of runtimes, the different types of runtimes, and even answering the most frequently asked questions.

How To Calculate Load and Run Time

The first step is to calculate the amount of energy your household uses.  You can follow these simple steps:

  1. Make a list of the most necessary items that you would need in the event of a power outage.
  2. Check the levels or user manuals of the devices to know the power consumption of each device.
  3. Add up the numbers that will give a number stating total watts, and multiplying it with the time you want to run will give you a watt-hour count.

You can divide the number by 1000, and the result will indicate kWh if that seems more suitable to you. For example, a freezer, a pump, and some lights in your house sum up approximately 300 watts.

If you run those devices for an hour, you will need a 300 watt-hour or 0.3 kWh capable generator. Runtimes vary depending on the type of generator, fuel type, and load on the generator.

There are two main types of generators: portable and standby generators.

How Long Can You Run A Generator Continuously

Portable generators are the most preferred ones for homes, small offices, or using it during an outing. Standby generators, on the other hand, are large in size and used in large factories, hospitals, or such buildings.

You can run a generator using gasoline, diesel, natural gas, or propane. Fuel type makes a huge difference in the runtime.

Calculating the runtime of a generator involves several efficiency factors. The equations may seem complex. Here, we have a simple version with approximate results.

For example, you bought a generator with a 5000W capacity, and you can get some information from your manufacturer. With a 50% load, which is 2500W, and a full tank with 5 gallons of gas, you might get an 8-hour runtime.

We can see another example of a diesel generator’s estimated fuel consumption calculation. An 8kW or 10kVA diesel generator can run on a one-fourth of the full capacity and consume about 0.8 liters of diesel in an hour.

Again, this is an approximate calculation and may not be completely accurate. You can see the variation in the runtime depending on many factors. If it is a gasoline-powered generator, you can get the same runtime with far less amount of fuel, which is convenient for a lot of people.

Running a Power Generator Continuously

You can answer the question after reading the owner manual provided by the manufacturer. Some generators are built in a way that needs fewer maintenance hours, where some need regular work.

The time for running a generator continuously depends mostly on the fuel tank capacity and fuel type. If you have a gasoline generator, you will have to give it a break to cool down the engine before refilling.

But with the right setup, you can make sure that your propane generator is running for 150 to 200 hours non-stop. It is recommended that you give some time to recover the motor’s capabilities after long runtimes.

Those are the estimations for the portable generators, and you can increase the time by getting a standby generator. With a standby generator from a renowned manufacturer, you can run it for 21 days.

Propane Runtime Vs. Gasoline runtime

So, you already have got an idea about the runtime of a propane generator and gasoline generator. Now, let’s compare the cost of both fuel types and then know the benefits as well as drawbacks.

Considering the same example, you will need 5 gallons of gas to get 2.5 kW of power for almost 8 hours. On the other hand, you can get almost the same amount of energy output using 6 liters of diesel.

Now, you can search for the fuel prices and see that 5 gallons of propane will cost you about $30 to $60. However, the price of diesel is far less than propane, costing you less than $4 for 6 liters. You can then calculate that the cost difference is almost 7 or 8 times

Both diesel and propane come with their fair share of advantages and disadvantages. Here are a few:

  • Work without pumps:

Propane can power up your generator without any pumps whereas gasoline requires pumps to provide fuel to the generator. Pumps can get into trouble, sometimes making gasoline inconvenient for some people.

  • Work without stabilizer:

If you are thinking about storing gasoline for a long time, you will have to get expensive stabilizers to prevent the fuel from going bad. But that is not necessary for propane as a good storage tank is enough for it.

  • Fewer maintenance hours:

Gasoline or diesel generators need more maintenance than a propane engine.  This makes it more convenient for busy people with less time for generator maintenance.

  • Less spills 

Diesel and gasoline run a high risk of causing accidents due to leaks or spills. This is not a problem faced when operating on propane.

  • Working in cold weather:

Propane can still perform in cold weather without losing its efficiency, which is not the case for gasoline or diesel.

  • Runtime difference:

Propane has less energy density means that the cost of running a propane generator is higher than a diesel generator.

  • Engine-friendly fuel:

Gasoline or diesel is considered to be engine-friendly fuel. This means that the engine runs for many years, whereas propane or natural gas can make the engine decay faster.


Frequently asked questions

Below, we will be answering some of the most frequently asked questions to better assist you with all your generator concerns.

Is it safe to leave a generator on all night?

This depends on your generator’s quality, capability, and ventilation. If you buy  generators that claim to run all night, you can rely on it, you can read our reviews to be sure about it.

Can you run a generator continuously?

Depending on the type of generator, you can run it continuously for a time period recommended by the manufacturer. Usually, a standby generator comes with a large tank capacity and high-efficiency motor to run continuously for a very long time.

Is it OK to let the generator run out of gas?

If your generator uses a pump to pump the fuel to the engine from the tank, letting the generator run out of gas will create a problem in the pump. However, running out of gas or another fuel type can’t damage the generator’s engine.

Can You Use a Generator in the Rain? 

The manufacturers discourage using the generator in the rain as it might create electrical shocks. You should keep it under a shade and use it in any weather condition without any problem.

Final thoughts

All the information above was curated to help you answer the question:  how long can a generator run continuously? 

Regardless of your conclusion, one of the most important things to keep in mind is safety. Storing large amounts of propane can be dangerous for homes. This is why many homeowners prefer gasoline.

Running a generator nonstop is easy to do with the proper equipment, preparation, and background information. With the information above, you are one step closer to safe and continuous backup power.


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