How long can you run a generator continuously? The answer depends on several factors, and we’ll address the major ones here.
Until You Run Out of Fuel
A simple answer to the question of how long the generator will run without stopping is: until it runs out of fuel. If you have a natural gas generator connected to a gas line, it will not run out of fuel and will run until the air filters clog or the oil gums up the motor. In pretty much every other case, if you do nothing else, the generator stops when it runs out of fuel.
A home generator connected to a 500 gallon propane tank could run for days to weeks, depending on your demand. A portable generator running off a gas tank will last several hours. A standard diesel standby generator has a 24 hour gas tank, though models with 48 and 72 hours’ worth of fuel are available.
Be careful about the run time statistics many generators advertise. When they say it lasts up to ten hours, it probably lasts eight. When they say it lasts ten hours at one quarter horsepower, the energy economy mode, know that that is at the lowest level – and the generator will last a fraction of that time if you’re running an air conditioner, refrigerator or other energy hog.
In general, you should expect a generator to last for several hours on a full gas tank. If you plan on running a generator all day, plan on refilling the gas tank at least once. Know whether or not the generator manufacturer considers it safe to refuel when operating before you just pour more fuel in.
When Maintenance Becomes Necessary
Though you may have a continuous fuel supply for a generator, you need to shut it down to do proper maintenance. Changing the oil is one of the most common maintenance tasks. Read your generator’s owner manual to know how often the oil needs to be changed, since that could be anywhere from 50 to 200 hours of run-time. If you haven’t used the generator in a while, know that the oil needs to be changed at least once a year.
If the generator is sitting in a dusty area or the air intakes are getting clogged, assume the oil is getting polluted and needs to be changed more often. Check the owner’s manual to know how often the oil filter has to be replaced.
Air filters should be checked on a weekly basis if you’re using the generator continuously. You may need to do this more often if you’re in a dusty environment like a workshop or outdoors. You can clean the filter with compressed air or water, though the air filter should be completely dry before you re-install it. Always turn off the generator before you take out the air filter to check it and/or clean it.
A general maintenance tip from the manufacturer is to turn off the generator periodically to let it cool down, whether or not you need to change the oil. Turn it off for at least thirty minutes every day or two.
Spark plugs need to be checked periodically, though you’ll need to check the manual to know how often they need to be replaced.
When Safety Concerns Make It Necessary
If there is an oil leak, you need to turn off the generator to eliminate the fire hazard. Most generators have an oil level switch that will shut down the ignition if the oil level gets too low.
If the generator is overheating, you should turn it off and let it cool off. Check the air intakes and clean them out. You can try to restart the generator at this point, but if it overheats again, shut it down and get it repaired.
Put your generator somewhere with good air flow. It should be at least fifteen feet or five meters from your home. This means you don’t want to run a generator inside an enclosed garage or closed-up shed, since you could suffocate if you walk into that space and stay for more than a literal minute. And make sure the exhaust is not venting toward doors and windows.
You don’t want to breathe in the carbon monoxide the generator creates. Put a carbon monoxide detector in your home. If the carbon monoxide detector goes off while you’re running the generator, you need to turn off the generator and open some doors and windows to get fresh air. There are some new portable generators with a built-in carbon monoxide detector, but not all of these will automatically shut off the generator if the CO levels are dangerously high.