Phil has been working as a technical engineer since his graduation, and has never thought of changing his profession. Also, he’s an avid fisherman and camper, so it’s not only work which makes him deal with generators.
Last updated: June 21, 2021
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Most of the time, you will only need to run your generator for a short period. Maybe you’re running power tools for a few hours or powering a tailgate. However, what if the power goes off for days on end? That’s far from unheard of after major winter storms, hurricanes, and other natural disasters.
In that case, you’re going to want to run your generator for as long as possible. Which begs the question, how long can you run a generator continuously? There’s no single time limit in answer to this question. Rather, how long you can run a generator continuously depends on what type of generator you have and, to a lesser extent, factors like temperature and cooling.
If you’re wondering how long you can run your generator continuously for, this article will explain everything you need to know.
How long can you continuously run a generator on gasoline?
If you have a portable gasoline generator, your continuous run time is the most limited. That’s because you can only run the generator until you run out of fuel in the tank.
You’re probably thinking at this point that you could simply pour more gas into the fuel tank without turning off the generator. However, that’s something you should never do.
Refueling the generator while it’s running runs the risk of starting a fire, since the heat and static electricity produced by the generator can easily spark gasoline.
So, the maximum amount of time you can run your gas generator continuously depends on its fuel efficiency and the size of your fuel tank. Most portable generators are rated for around 4 to 10 hours of run time if you’re using all of the available wattage. If you’re using 25 to 50% of the available power, you may be able to run your generator for 12 hours or even more. Even the highest-capacity gasoline generators on the market are limited to a maximum of around 24 hours of run time.
How long can you continuously run a generator on propane?
If you have a propane generator, the amount of time you can run your generator for is dramatically longer. That’s because the fuel tank is the propane canister, rather than a reservoir inside the generator itself.
On the one hand, you could go out and buy a massive propane tank – off-grid homesteads and rural homes often have propane canisters that can hold hundreds or thousands of pounds of propane. However, there’s a simpler solution.
If you have two or more propane canisters, you can connect them together via a stopcock valve or changeover regulator. In this setup, the generator is drawing propane from just one of the canisters while the other canister is closed. Once the first canister runs out of fuel, you simply switch the valve to start drawing propane from your second canister. You can keep swapping in fresh propane tanks for as long as you have them available in this setup.
However, that doesn’t mean you can run your portable generator forever. Most propane generators will run out of engine oil after about 150 to 200 hours of use. At that point, most modern generators will automatically shut off in order to protect the engine from permanent damage. (It’s a good idea to turn the generator off before the automatic shutoff kicks in, since you’re already risking engine damage at that point.)
So, you can let a portable propane generator run continuously for around 150 to 200 hours.
How long can you run a standby generator?
What if you have a whole-house backup generator? In that case, you really can run your generator for days on end.
Standby generators are built for providing power for multiple days in a row. They’re built with larger engines that are designed to be more efficient when running continuously, and they won’t quickly run out of oil like portable generators will.
Most standby generators are rated for up to 500 hours of continuous use. That’s nearly 21 days of power without turning off your generator. In theory, you could go even longer – but there are no automatic shutoff switches to prevent you from damaging your expensive standby generator if you go beyond the manufacturer’s recommendations.
Importantly, that 500-hour rating assumes you have enough fuel to power your generator for that amount of time. If your generator is connected to a natural gas line, this won’t be a problem. But, if you’re using propane, you will need a several-thousand-pound propane tank to keep a standby generator running continuously for three weeks.
What can you do to run your generator longer?
One of the biggest issues that you face in running your generator – especially portable generators – for extended periods is heat buildup. Most portable generators are built to dissipate heat over time intervals of one day or less. Once you get into multiple days of continuous use, as is possible for a propane generator, you run the risk of overheating your generator and causing permanent engine damage.
To avoid this, it’s important to do everything you can to keep the generator cool. That means ensuring there’s a breeze, potentially from a fan, to blow hot air away from the generator. You will also want to keep the generator in the shade as much as possible.
Ultimately, there’s not much you can do to run your generator beyond the limits imposed by fuel or oil changes. The key is to make sure that your generator won’t suffer permanent damage from running it continuously up to these limits.
The rated run time for propane generators isn’t necessarily longer than for gas generators. But, since you control the fuel reservoir with a propane generator, you can run it for significantly longer than a gasoline generator. Most gasoline generators can run for less than 24 hours, while you could run a propane generator continuously for up to 200 hours.
If you have a gasoline generator, you should never refuel it while it’s running. Pouring gasoline into a hot generator is very likely to cause a fire. If you have a propane generator, though, you can refuel the generator. In this case, you’ll need to hook up two propane canisters together using a stopcock valve. This isn’t so much “refueling” as simply switching propane tanks without turning off the generator.
If your dual-fuel generator supports seamless switching between fuel sources, then you can switch from gas to propane without turning off the generator. However, you can’t switch back from propane to gas afterwards, as you should never refill the gas tank while the generator is running – even if it’s running on propane at the time. If your dual-fuel generator doesn’t support seamless fuel switching, you will have to power it down before changing fuel sources.
If you can help it, you’ll dramatically prolong the life of your generator and reduce wear and tear by giving it a break once a day or even once every few days. Portable generators simply aren’t designed to run continuously, even if you can do it.
Unfortunately, there are times when you will need continuous power for an extended period. So, how long can you run a generator continuously? A gasoline generator is limited to its rated run time, while a portable propane generator can run for 150 to 200 hours at a time. Standby generators are the best for continuous power demand, as they are designed to run for hundreds of hours without causing excessive wear.
Keep in mind that running a generator continuously for days on end requires a lot of fuel, so you’ll need to plan ahead. Heat management is also important, especially for portable generators, as heat buildup can cause permanent damage to your engine.