Generators are a common fixture in prepping and elsewhere in society wherever you’ll find a need for electricity regardless of a lack of power infrastructure, or a temporary disruption in an existing grid.
Whenever you lose power due to bad weather, a prolonged grid-down situation, or even the toppling of society in general, you’ll be glad you have a generator fueled up and ready to go, so you can keep your much-needed electronics and appliances functional.
The commonly held theory states that you can run your generator as long as the fuel holds out but is this actually true? Are there other considerations that will impact the “up time” of a generator?
Just how long can you run any given generator safely? A generator can run anywhere from a couple of hours to a couple of days, or even a couple of weeks before it needs shutting down. This depends upon several variables such as the size and efficiency of the engine, the type of fuel it uses, how much heat it can sustain, along with any required maintenance intervals.
Running a generator beyond the manufacturer’s recommended interval is generally a bad idea, and should be avoided.
There is a fair bit to consider when deciding on how long you may run your generator safely without risking damage, and the remainder of this article we will dig into those factors so you can make an informed decision.
Size
The size of the generator typically determines the size of the engine, and often the efficiency. This can inform the user of how long you can expect the generator to perform before needing to be shut down for reasons aside from fuel depletion.
Generally, smaller, portable generators will only be expected to run for a couple of hours before needing to be shut down; their fuel tanks will only last that long, typically.
Much larger fixed site and standby generators will often be connected to fuel tanks or dedicated fuel supplies that can run them for many days or even weeks in certain circumstances.
Despite having a nearly bottomless supply of fuel, these larger generators may only be expected to run for several days or a couple of weeks before needing to be shut down for other reasons.
While there are some small generators that can run for extended periods and occasionally you will find larger generators that are not designed to run for nearly as long as one would think you can use the size of a given generator to inform your opinion lacking any definitive guideline or operator’s manual.
Fuel Type and Supply
The type of fuel your generator uses is a significant factor that will determine its run time, and it has nothing to do with efficiency as you might be thinking. Common generators will usually run on one of two types of fuel, gasoline or propane.
Gasoline generators in general have shorter up times compared to equivalents that run on propane because gasoline generators, especially smaller portable ones, should never be refueled while they are hot. And, believe me, they will get hot once they have been running for just a little while!
Pouring gasoline into a hot generator risks everything to blow up, something you definitely don’t want. For this reason gas generators that run out of fuel must be allowed to cool to a safe, or at least safer, temperature before being refueled.
Depending upon a gasoline generators capacity this could be anywhere from a couple of hours to upwards of ten hours. Very few portable and household backup generators that run on gasoline have a fuel capacity large enough to last for days.
Propane generators have an advantage in this regard since they are typically set up to draw fuel from one of several connected, common propane tanks. This allows the operator to easily switch out tanks when one runs dry while the generator safely operates from the spare.
At the very least this allows you to scramble for a fresh tank to feed to a propane generator should it run out of fuel without having to wait for it to cool down.
Heat
Heat is a constant concern for any generator, and though modern ones in good repair will build up heat comparatively slowly over time, very few are the generators that are able to run indefinitely without suffering any problems from accrued waste heat.
b than ones operating in cold environments or benefiting from heat management technology.
Depending upon the type and design of your generator it might shut down once it reaches a certain temperature, once it has sustained a certain temperature for a length of time or it might not shut down due to heat at all barring malfunction or part failure.
Regardless of your generator’s heat management function or lack thereof running any generator for a long time at a high temperature will accelerate wear, and generally lead to more intensive maintenance.
Maintenance
Every generator is different when it comes to maintenance. Some will need maintenance more often, some less. Some manufacturers recommend you do cursory maintenance every time you shut your generator down to refuel it.
Generators that are well-maintained can typically run longer with fewer ill-effects than ones in a poor state of repair. Generators that are poorly maintained or ones that are considered maintenance hogs will require nearly constant maintenance unless you want to pay the piper.
This is an important consideration depending on what you need your generator for. A portable generator that can only run for a handful of 4 or 5 hour cycles before it needs minimal maintenance (in the form of an oil top off or something similar) might not be that big of a deal.
A household or standby generator that requires maintenance after only 72 or 100 hours of up time could be a poor bargain; that is only a few days of run time after all.
No matter what kind of generator you are operating, make sure you follow all prescribed maintenance intervals and violate them at your own peril; a proper breakdown is going to be very difficult and expensive to fix, especially if you are already without power!
Conclusion
Your generator, depending upon the size and other variables, can run anywhere from a couple of hours all the way through a couple of weeks.
You will have to understand the ins-and-outs of its fuel type, heat management and prescribed maintenance intervals in order to ascertain how long you can safely run your generator without undue risk of damage or wear.
Exceeding the maximum uptime on your generator will only lead to a breakdown and loss of capability.
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In my experience as an Emergency Manager, we use 240 hours or 10 days continuous as a “guide”. Your comments on the status of the gen set before operation plays a big role in this. I can tell you that I witnessed some really catastrophic failures in NYC after Sandy due to lack of planned maintenance.
The loss of the capability is not worth bypassing some good old maintenance.