How Long Can My Generator Run For?

Having a generator is a nicety for some and an absolute necessity for others. It all depends on where you live and what you can expect from your winters or from your severe weather season. Where I grew up, in rural Michigan, the possibility of a power loss during a winter storm was real and could happen often throughout those winter months. You either had to tough it out and throw some wood in the fireplace, or you pulled out your generator and got some that much needed power back on.

During these power loss events a common question that is asked is how long can my generator run for? Can I run it for days on end? Or, should it be used sparingly? Well folks, to answer this we first have to look at a variety of variables and understand what type of generator that you have.

Can Generators Run Indefinitely?

First and foremost, please remember that generators are used as a backup source to your regular power. They are a temporary alternative power replacement. The key word being here is temporary. They are not intended to replace your utility company and nor should they. Remember, generators are not the same as solar panels or other alternative power sources. Generators are designed as an emergency power source, and nothing more.

If a generator is kept running and running constantly then you are going to run into mechanical problems and maybe eventually engine failure. Generators have an engine and just like any other engine, it cannot be run constantly. I know I wouldn’t do that to my car, would you? So, what is the ideal time? How long should you run it for?

So, How Long Can They Run For?

Ok, so now that we know that generators cannot be run forever, we now need to figure out how long your generator should/can run. This is where things can get a bit tricky. That’s because of the variables that we have to consider. This could be the wattage size of your unit, the capacity or how much power you are demanding, the fuel type, and lastly the fuel tank size.

Let’s take a look at the fuel tank size first. Assuming that we are dealing with a portable generator the fuel tank size can range from a few gallons all the way up to ten gallons. You may find some even higher then that. Obviously, the larger the fuel tank the longer your generator will be able to run. Now, from what I have read a gallon of fuel can last anywhere from one and a half hours upwards to three hours. It all depends on the efficiency of the model you have AND the capacity that is being used. As an example, if you are using only twenty-five percent of your five-thousand watts generator then you can expect to see around three hours per gallon of fuel. (Maybe even closer to four.) But, in the same example if you are at one-hundred percent capacity and are using ALL of your watts then you are going to be around one-and a half hours per gallon fuel.

Westinghouse WGen5500
Westinghouse WGen5500

Now that we have that math figured out lets do a few real world examples. Let’s pretend you have a generator with an eight gallon tank and are running at about fifty percent capacity. We’re going to say you are consuming around a gallon of gasoline every two hours. So, by doing the math we can see that your generator will last sixteen hours before it needs to rest, be refueled, and reoiled. In a similar scenario with a four gallon tank and at one-hundred percent capacity you may only get a few hours out of the generator before it needs to be maintenanced.

Another variable to throw in the mix when dealing with portable generators is that some of these units are able to take propane tanks instead of gasoline. These are the same kinds of propane tanks that you use on your grill. You just pop it in and then you have your fuel source. The good news here is that propane is more efficient then standard gasoline. In fact, it burns less volume per hour by a factor of two to one when compared to gasoline. This could add an additional twenty-five to fifty percent to the gallons of fuel per hour we discussed earlier.

All that being said, a portable generator can run for as low as a couple of hours all the way up to twenty-four hours. It all depends on those circumstances we mentioned above. Just remember folks, that portable generators are NOT meant to run forever. They are a temporary solution and that is all.

Standby Generators

If you are looking for a generator that can you give you that needed power for longer periods of time then it may be time to consider purchasing what’s known as a standby generator. These generators hook up directly to your home, are immobile, and provide a substantial amount more power/wattage when compared to portable generators. On top of all of that these standby systems can actually hook directly up to your gas line or into your propane tank, and when I say propane tank I do not mean your standard four and a half gallon tank. No, I am talking about your big tanks you see out in the country: The five-hundred gallon all the way up to one-thousand gallons tanks.

With a tank that size you can safely assume that you will be able to run your generator for a much longer time then a standard portable unit. A propane powered standby generator typically burns between two to three gallons an hour. That equals out to about one week of constant power using a five-hundred gallon tank and about two weeks using a one-thousand gallon tank.

Depending on how much you want to invest into your generator some homeowners opt for two propane tanks. One of these tanks is for their standard home usage such as ovens, furnaces, and water heaters. The other tank is specifically meant for their generator. This gives the homeowner peace of mind that if they do have a power loss event that they will be able to run their generator up to two weeks.

While two weeks is a long time, remember that it is not recommended to be running your generators constantly. Just like anything else, they need a break every once and a while. Also, remember to perform proper maintenance on your generator rather it be a standby or a portable system. For more on maintenance you can click here to be taken to our Generator Maintenance Guide.


Well folks, that about covers it for how long you can run a generator for. The short answer is, there is no set limit. It all depends on the model, the watts, the capacity, and the fuel tank. If you are unsure it is always best to consult with your product’s instruction manual.

If you are in the market for a generator then I suggest you check out our Best Generators Guide by clicking here. Within this guide we go through what generator application you need, what size you need, and provide some of the top brands and models for each category.

After purchasing your generator you may find yourself unsure on how exactly to be safe when installing and running your new tool. The best option here is to read through your instruction manual but we also offer a Generator Safety Guide here at ToughAssTools which can be found by clicking here.

Lastly, please note that this article is designed to give advice and is for informational purposes only. We here at ToughAssTools are not liable for any property damage, fire damage, personal damage, or any injuries from installing or running a generator.

Thanks for reading,

Alec Johnson


You may also like