Rankedgenerators is audience-supported. When you buy through links on this site, we may earn an affiliate commission that we use for site maintenance. Learn more


How Long Can a Generator Run – All Factors Considered!

how long can a generator run
Written by Jamie Masterson

Generators are innovations that help us run operations like power drills or picnic lights, even when there’s no immediate source of power. Even when there’s a power outage, a generator could last you for at least a couple of hours. But the question is for how long can the generator prolong delivering power?

We can all agree that it is quite handy to have a generator but not feasible to make it last for an extended period of time. We can derive a few hours or maybe a couple of days’ worth of power but only until its limitations aren’t exceeded.

How Long Can a Generator Run?

How Long Can You Run a Generator Continuously

1. Engine size

The size of the engine Motor can be determined by the horsepower production (denoted by kW) capacity of the generator. The running time and the power of production are directly dependent on the size of the engine. There are pros and cons related to having both of a large-sized engine and a small-sized engine.

  • A small engine implies that occurrence for frequent fluctuations in power at the cost of the efficiency of the overall generator. On the other side, these engines can run for a longer period of time by converting battery power to higher DC voltages. They are mostly suitable for short backup power for houses, camping trips and picnics.
  • A large engine can be more beneficial if you want to produce constant electricity on a larger scale. However, the bigger the size, the greater the maintenance since there will be a lot of carbon disposition in the main unit. Over a considerable period of constant power supply, you might observe signs of the machine slowing down, further reducing the time for which it should be kept running.

2. Types of Fuel

Generators can produce electricity only with the help of fuel combustion. They vary depending on the type of fuel used. Different fuels such as diesel, petrol and more provide varying amounts of power while also be accompanied by their own advantages and disadvantages. Even so, the running time of generators depends on the efficiency and burning rate of these fuels. To answer the question that how long can a generator run, fuel is a significant role to play.

a) Diesel

If we talk of Diesel, then it is the most commonly used fuel in generators as it is the least flammable fossil fuel. Diesel affords more efficiency on the main coil of most generators providing stand by power. A diesel-operated generator can run for as long as 30,000 hours without a lot of maintenance. On The other hand, Diesel is very easy to store while also being deemed as the best affordable fuel. Overall, Diesel is a very versatile and good fuel with Generators.

b) Gasoline

Though diesel can provide you with a longer running time with affordable prices, it is eventually not good for the machine life itself. Diesel can get accumulated in the main machine of generators; hence the substitute of Gasoline is a good option. The lifespan of Gasoline operated machines is longer than that of diesel. You can run a Generator with gasoline for approx. 1000 hours. Gasoline although, is more flammable than diesel, and this creates an issue.

c) Propane

Propane is a new material in the market when comes our list of generator fuels. Propane is not that efficient with continuous running but has its own advantages over other fuels. If you are using a portable generator and you desire to work with a continuous source of propane, then it can run a generator for 200 hours or more continuously. This means you will have a continuous supply of electricity from a generator for more than 8 days with propane.

d) Petrol

Petrol is most probably the least favored fuel for generators. It is not preferred to refuel petrol in a running generator given its drawbacks. Using petrol is comparatively risky since it is the most flammable than all other fuels. It is better to have petrol powered generator cool down before refueling it. This also means that at one full tank, you can only run the generator for 12- 14 hours.

e) Natural Gas

Natural gas is one of the new fuels for generators these days. It is a safe source, while on the other hand, it is also bio-compatible. Natural gas is used in heavy and modern generators as refueling becomes very easy. If you are guessing how long can a generator run on Natural Gas, then you can expect it to go for a week without any problem. However, some more efficient generator models can run with natural gas for months without continuous refueling.

3. Fuel Tank

The fuel tank decides the amount of fuel a generator can bare at a time which ultimately answers its running capacity. It is quite simple here. The bigger the fuel tank, the more fuel it sustains for burning and the longer it keeps on running.

Different Types of Generators & Their Specifications

1. Standby

A standby generator is basically a fully powered, automatic generator. It can provide you with a huge amount of electricity, and it does require maintenance to work. It is often huge in size and can provide a permanent solution for electricity production.

  • Diesel – It can work for more than 20,000 hours
  • Petrol- For 12 hours with a full fuel box. (Refueling while working is not advisable)
  • Propane- For 200-300 hours
  • Natural gas- For 200 hours

2. Portable

These are small generators that are easy to move from one location to another. These days’ people at camping sites, functions, and events find it a very useful device. People who require an electric supply for a limited amount of time for their own personal use, can find it to be a very reasonable asset.

  • Diesel – For 300-400 hours
  • Petrol- For 12 -16 hours with full fuel.
  • Propane – For 40-50 hours
  • Natural gas- For 20-30 hours.

Generator Fuel Saving Tips

  • Regular servicing will give you better efficiency with any fuel.
  • Carbon cleaning is the key to using your fuel at the max.
  • Overloading the fuel is never useful.
  • Content is a must to save fuel.
  • Allow the fuel standing time before using the generator.


1. Gas vs. propane generators: which will run longer?

Ans. Speaking of running time, propane can lag behind gas here, but it is a better fuel for both the generator and the environment. But Gas wins the race.

2. How long can I run a dual-fuel or propane generator?

Ans. A Dual Fuel or Propane generator can work continuously for 13-15 hours without refueling.

3. How much fuel does a gas generator hold?

Ans. Assuming that we are talking of a stand Gas generator then, it can hold approx. 20-25 gallons of fuel at once.

4. How long can I run a backup generator?

Ans. A backup generator is also a standby generator that can run for more than three weeks at a time, and a portable generator can run for 2-3 days.

About the author

Jamie Masterson

With decade-long experience as a generator technician, Jamie has worked with USA’s top generator manufacturers and suppliers as an independent contractor.

The long years of service to the industry has taught Jamie the ins and outs of troubleshooting, repairing, and maintaining all kinds of generators in home, industrial and outdoor settings.

Jamie thinks this platform is a great opportunity to share his tips and tricks with you so you can make the most of such power equipment for better living.

Leave a Comment