If you own a generator or thinking about getting one, it will be interesting to know the answer to this question, how long can you run a generator continuously?
We require generators for different applications.
Most of these applications require a few hours of running.
But prolonged power outage could require you to have a generator with extended runtime.
Thus, you’ll need to get an answer to the question above.
Generally, generators are a source of power for backup and are not designed to operate continuously.
The critical determinants
The critical determinants of how long your generator could run continuously are as follows:
- Engine size
- Type of fuel
- Fuel tank
- Power output
How long can you run a Generator Continuously?
A generator can run continuously for 7.5 to 12 hours on average. Different generator models have additional run time, as illustrated below:
- APG2000IS All Power America runs for about 9 hours
- The average runtime for the 30676 Briggs and Stratton generator is 14 hours.
- The 3800W Champion Dual Fuel generator has a runtime of 9 hours
- The Durostar DS4000S generator’s runtime is 8 hours, while that of DuroMax XP4000S is 8 hours.
To sum up this section, we have seen that many factors determine the average generator runtime. But on average, you could expect an excellent generator to go somewhere between 7.5 and 12 hours.
Running Time of a Generator
Some models are designed to provide power for up to eight hours, some in the range of twelve, and some others can continue to work for quite some time.
However, it is not good to keep the generator running for a long period of time, like days without time for them to rest.
This mainly has to do with the way the generators are assembled.
Like any motorized machinery, the engine requires fuel, grease, and maintenance.
When you cut off the supply of liquid propane or natural gas from your house, then your generator is a large paperweight. Some generators also require fuel as lead-free gasoline.
At the time the tank dries, most models will automatically shut down to avoid damage to the machine that can’t be repaired or difficult to be repaired.
Can you run a generator overnight
Yes, you can run a generator overnight, but there are a few problems that you will have to deal with.
Like I mentioned at the beginning of the article, most generators can run about 8 hours before empty their fuel tank.
This is enough gas for overnight. For example: (From 23 h 00 pm to 7 h 00 am) is 8 hours. There 3 problems that you will deal with which the following:
- CO: If you have a CO detector installed that will cover you there.
- Noise: If you have a quiet generator, you do not have to worry there too.
- Thieves: If you are in a secure neighborhood, there will not be a problem too.
Below are some of the best generators with Fuel tank capacity and run time.
|Image||Name||Price||Gasoline Run Time||Key|
|Gasoline Capacity (gal.)||Propane Run Time|
|Champion 3,800||Read Full Review||9.0 at 1/2 Load (h.)||Dual Fuel RV Ready Generator with Electric Start||3,800||3.4||10.5 at 1/2 Load (h.)|
|DuroMax 12,000 XP12000EH||Check Price||Max 9,500 Running||Dual Fuel Electric Start Portable Generator,||12,000||8.3||Max 9,500 Running|
|Champion 7500||Read Full Review||8.0 at 1/2 Load (h.)||Dual Fuel Portable Generator with Electric Start||7500||6.1||5.5 at 1/2 Load (h.)|
How long can you run a Generac generator continuously?
Just like many other generators, Generac generators can run for a long time but some things have to be supplied at all times.
This type of generator was designed specifically to provide up to around 3000 hours of service.
However, if things like proper usage, maintenance, and oil are not provided, it won’t last for long.
Your Generac generator may be run by three types of fuel that include propane, diesel and natural gas.
All this must be kept in place so that it runs for the expected time and they can determine the time it runs
If natural gas used to use, then it is not expected to shut down any soon not unless the line of gas goes down.
Consequently, if that happens, it will not be expected to run for long since they don’t run since there is no fuel tank required here.
If it is diesel or propane, the fuel tank will be available and therefore it can run for 24 hours if the tank is full.
There are other tanks that go for 48 hours and some go for 72 hours.
In summary, the generators have an interval of 200 hours for changing the oil and therefore, that will be the maximum time to run it until you change the oil. Read more about the best oil for a generator.
How many hours does a generator last?
Several manufacturers specify separate maintenance plans for their generators.
During each administration interval, change the oil and oil filters, replace the air filters and change the starting plugs.
Some require the control and adjustment of the clearance of the valve.
Portable generators usually have a shorter schedule for maintenance.
The average is probably around 100 hours, but you have to check your particular model.
The generators specifically made for the prime power have longer hours.
Diesel engines, in particular, can continue to operate for a long time provided the oil does not degrade.
The large filters and a large oil reservoir could extend the running time, but frequent oil checks are still required.
When using a generator, check the oil continuously at regular intervals maybe after 24 hours but it should not be overfilled.
Maintenance is a critical consideration.
If you live where frequent blackouts last for days or are sensitive to weather-related disasters such as hurricanes, make sure the interval for generator maintenance is not less than seven days of operation or approximately 200 hours.
Maintenance allows the generator to last for the expected hours and only if the generator is powerful enough for the job.
How long will a generator run on one gallon of gas?
Gas is one of the sources of fuel and the easiest to acquire.
Despite that, it is very flammable and dangerous to store in large quantities.
Gas prices are to a certain extent expensive and tend to be the most efficient approach to operating a generator for a reasonable time.
Mostly, portable generators will continue to run on gas without any problems.
A good 5,000-watt generator will use about 18 gallons of gas in 1 day / 24 hours.
This makes it extremely unrealistic and expensive when using it for a long time.
There are a number of efficient gas generators that can be convenient to be used at homes.
Typically, a 1-2 gallon fuel tank can last from 8 to 10 hours.
Definitely, a gallon cannot last for more than five hours on average for most generators.
This is the reason why most people are trying to use inverter generators.
Most of them offer an environmentally friendly or economical mode that fluctuates depending on the load requirements.
Generac 7117 GP2200i 2200 Watt Portable Inverter Generator – Parallel Ready on Amazon is one of the generators that are very on gas. With only 1.2 fuel tank capacity, you can run it up 10 hours straight.
It is an economy mode that gives you more on the tank and reduces the noise at the same time.
How long will a 500-gallon propane tank run a generator?
People with such a question only intend to know how costly it is to run a propane generator at home.
This is a decent question in light of the fact that there are some important benefits to using these devices.
There are many disadvantages too that should be considered too.
Unfortunately, there is a general rule that propane generators are not as efficient just like diesel or gasoline generators.
The reason why they can consumer higher fuel amounts is all about physics.
The measurement of the energy that propane can produce when burning is just less than that of gasoline or diesel.
In one hour, propane gives out 92000 BTU’s in one gallon while gasoline, on the other hand, produces 114000 BTU’s.
This is a simple illustration that a high amount of propane will be consumed in an hour compared to gasoline or diesel.
From the above estimations, we are able to find out that a 5000- watt engine can use a tank of 500 gallons of propane can run a generator for about 920 hours.
Do generators run on gas?
A common question asked when purchasing a generator is do generators run on gas and if so what type of gas I required.
There are 7 types of generators: gasoline, diesel fuel, biodiesel, emulsified diesel, propane (vapor & liquid), hydrogen and natural gas and 3 subtypes: portable, inverted and standby.
The most environmental and affordable generator of the 7 is the Natural Gas generators.
Natural Gas Generators
The natural gas generator allows for a cleaner burn and very little waste. They run quietly causing less noise pollution.
Due to it being natural gas it requires a natural gas line to run to the operation site preventing the generator from being portable.
This causes higher installation costs although the generator becomes self-sufficient where you won’t worry about the fuel and it needs to be refilled.
Unfortunately, these generators don’t last as long as the others, and broken lines can lead to a dangerous leak due to the fuel being more flammable than diesel.
Although natural gas generators’ costs are more affordable it is still a whopping $1,000 to $5,000.
How long can a natural gas generator run Continuously?
They can run for approximately 200 hours just like the other prime power generators. So long as the gas is supplied, they will not easily run out.
At this point, the mix is compressed by a piston hence leading to power production at the end. How long they can continuously run depends on a number of things.
They are usually attached to a supply that is given by the utility company.
It can, therefore, be used for a long time and can only run out if the line of gas goes down.
Just as their name suggests, they only use natural gas to produce power to run homes and devices. Since they also need maintenance schedules.
Many people wonder how long it can take a natural gas generator to run continuously? There you have it.
You should understand these generators are run by natural gas.
In the generator, the engine that combusts internally injects a combination of air and fuel into the combustion chamber.
How Long Can a Diesel Generator Run Continuously?
Diesel generators are cheaper and efficient when using them at home as a backup for power outages.
The question of how long it can run continuously can be answered in different dimensions.
But they all bring us to one idea that fuel must be provided.
Other than fuel, lubrication and seizes should be checked at all times.
Maintenance schedules should be there and on average, it should be like 24 hours a day.
This is to check that the pistons and camshaft or any other parts that are critical do not wear out.
The generator cannot run out not unless fuel is used up.
However, if someone keeps refilling the tank continuously, there will be another problem.
This will be on how to change the oil without stopping the engine of the generator.
You just need to stop it for around fifteen minutes for servicing then it continues working. Check out best generator deals on Amazon
To avoid such issues, one can use two generator sets of diesel which will allow for synchronization and change during the time of service.
How Long Can you Run a Backup Generator?
Many generators can run for a long time but the constant factor to be available is fuel.
However, they cannot run for long periods of time since they have to shut down for servicing and then continue working.
Additionally, it depends on the type of machine that you will be using as your back up generator.
Some choose to use portable generators as a backup.
And it is clear that they may not have problems with knowing how long they can run them.
This small generator can only run continuously for around 11 to 18 hours a day.
When talking about fuel, there are those that use propane or natural gas.
The most important thing here is that they should be well maintained so that they keep running.
If for instance one is using the Generac generator that operates on propane, it is able to run for 24 hours a day for the whole week or even more.
How Long Can a Standby Generator Run?
Most of the standby generators can run for as long there is fuel supply to the generator.
Most of the standby generators do not require a fuel tank since they are run by natural gas.
Since there is a supply of natural gas from your utility company, they can run for a very long time.
In the case where the power outage is extended for some days, you will have a problem if you are using a diesel-powered machine.
Most of them have tanks that can only run for 24 hours.
Forgetting about the fuel type and its supply, it is advisable to periodically shut down your generator for purposely to cool the engine.
This can be during a sleeping time or working hour when not at home.
This can help you to check the oil level which should be added and not overfilled.
Generally, they can run for around 24 hours which will require fuel, oil check, and other maintenance.
How Long Can you Run a Generator on a RV?
Just like the other generators, they can run depending on the fuel supply.
Most of them use propane, diesel or gasoline. If the diesel is used, you need to use the same fuel source for both your generator and the RV hence avoid confusion.
Diesel can manufacture more power than propane hence it is advantageous.
Most of these generators can burn like 18 gallons of fuel in 24 hours and therefore you need to get some fuel for the RV.
They generally run for around 24 hours and after that fuel and maintenance will be important.
How long will a generator run on 5 gallons of gas
There are some specific generators like the Honda EU generators that manage the power output and engine speed.
It can also determine the devices that use the power hence identifies the amount of power required.
If the devices are not many, the generator will run half of its speed hence meeting the required demands of electricity.
Some generators can consume about 5 gallons in a period of 8 hours depending on the load on it. The Honda generators can as well use 2.5 gallons of gas in 24 hours.
Generally, the load applied to the generator can determine how long the machine can consume five gallons of gas. Learn more about how much gas a generator use per hour here.
How long can I run my Briggs and Stratton Generator?
It is a powerful and versatile generator that is easier to transport. What you should realize is that most of the generators running time depends on fuel availability.
Unlike other large generators that are used to provide prime power, this type is small and can be used in small homes or even during a time for camping.
It has a small tank of fuel and therefore, it obviously cannot run for a long time.
For starting watts, it has 2200 and 1700 running power watts hence it can averagely run for 8 hours on 25% load in a one-gallon tank.:
How long can you run a portable generator
Portable generators can be used for everything, such as lighting up your campsite or powering your outdoor activity.
However, one common question for first-timers or potential customers is, “how long can you ran a portable generator?” Well, the answer to this question can be more complicated than expected.
One thing that stands out is portable generators are designed to source power for back up. They are not meant to operate continuously.
Besides, the amount of time a portable generator can run solely depends on the type of the generator as well as the type of fuel used.
Some generator models are designed to provide power for up to eight hours, some twelve hours, and some even more hours.
However, it is recommended not to keep your generator running for a more extended period i.e., days or weeks without resting.
Remember your generator needs greasing, maintenance and fueling. As such, after running for some time, turn off the generator for some rest.
If you are using gasoline on your portable generator, the chances are that its running time will be most limited.
Nevertheless, if you are using propane as your fuel, your generator will always run for long.
This is because propane provides you with options for continuous refueling.
How Long Does it Take for a Generator to Run Continuously?
Generator continuous running time
A generator is a machine that is used to supply power in case of a power outage. It converts mechanical energy into electric energy.
You’ll find that in everyday activities we do require some source of power.
May it be cleaning clothes using a dry cleaner, or even watching your favorite movie just to name a few.
This is why you need to have a generator that can power your machines in case of a power outage. Some of the questions that we’re going to answer in this section include:
• How long can a generator run?
• Can you opt for a generator as the main power source?
• What makes a portable generator not last long?
1. How long can generators run?
Generators have different continuous running time depending on the model. Check out best generator deals on Amazon
Some generators are designed to power your various appliances just for a few hours, a day, or two at most depending on the type of the generator.
Your generator requires some time to rest so that you can lubricate it, re-fuel it, as well as cool it down.
Moreover, generators are among the most splendidly amazing machines whenever made.
No one in the lit-up world can live without control (we need the capacity to utilize the Internet, right?), and one of the most recognizably disgusting things to strike whole urban regions out of the blue is control blackouts.
As of now that the lights go out, it’s in every practical sense each man for himself.
At the point when all is said in done, generators, as a wellspring of fortification control, are not proposed to run perseveringly without end.
A couple of models are made to offer the capacity to as long as eight hours, someplace to the extent of twelve, and some can continue running for a guaranteed long time.
In any case, not the smallest piece should you keep your generator running for an imperative long time, months, also years without rest?
This prevalently has to do with the way where generators are made. Like any bit of equipment with a motor, the motor requires fuel, balm, and backing.
At the point when your home’s liquid propane or oil gas supply is cut, by at that point, your generator is an unbelievably enormous paperweight.
2. Can you opt for generators as the main power source?
Standby generators are designed so that they can provide an alternative source of power in case there is a power outage.
It might be costly for you to choose to use a generator as your main power source since it’s expensive to convert LP to electricity.
3. What makes portable generators not last long?
You’ll also find that portable generators require regular maintenance because of the fuel they use. You might.
This makes then not last for a very long period. If you run a portable generator for a very long period continuously even if it has a cooling system it will eventually fail.
How long do generators last?
An additional generator is an excellent effort for your home or business, so you should make sure that it will work as long as possible.
You will tend not to spend a large number of dollars on the fact that within five years will become inoperable. Or, on the other hand, maybe you need something you can rely on.
In particular, it is essential to consider the sections that provide the generator of assistance to the extent possible:
A brilliant brand with a reputation for long-term use.
Connects to the generator base, which visualizes how the station is configured correctly and offers you solutions to ensure the generator continues to run.
The usual assistance that the generator provides each time is required. Maintenance is the best way to deal with monitoring problems before they interfere with the generator.
An optional correlation test allows your relationship with the generator to determine when the problem arose so that it can be fixed with the most appropriate opportunity.
Do this without help to strengthen the wires that keep the long weekend and fight the generator.
For example, when checking online, for instance, One Plus from Kohler, you can quickly check the operation of your generator.
By following these guidelines for the Alliance Generator Proposal, you are guaranteed that your generator will last for 20 years as planned. Fortress generators must not surrender after 5 or 10 years.
In any case, please note that if the unit is air-cooled and not a liquid-cooled unit, it does not depend on continuous operation every day.
If you try to launch an innovative air cooler, you can assemble it by then.
Again, your relationship with the generator must be raised to ensure that you choose a generator that is valid for you, what support plans are available to you, and what you can do to ensure your generator runs for a long time. Read more About Generac Home Generators here.
How long will a generator run on one gallon of gas?
Numerous factors determine a generator’s fuel consumption rate.
For example, different fuels are used up at different rates depending on the type of generator.
A generator that uses gasoline may require more fuel to keep it running than a diesel generator.
The difference is because of the nature of the fuel and how it burns when being used up.
Diesel being a heavy fuel, a little goes a long way. With everything constant, a diesel generator will run longer than a gasoline generator. Similarly, a propane generator will utilize more fuel than a generator fueled by gasoline due to the fuel used.
Another factor that can lead to a difference in fuel consumption is the load connected to the generator.
The more things the generator powers will ultimately affect how much gas you will use in the long run. If the load put on the generator exceeds half the peak rated load, you will use fuel faster than if the generator was powering fewer appliances.
Also, the output power generated matters. A 5000-watt generator will require more fuel than a 2000-watt generator because it produces more power.
Consequently, a standard 5000-watt generator running on 1 gallon of gasoline at half of the peak load will stay operating for slightly over one and a half hours. Therefore, it will be more expensive to run under extensive use.
Frequently Asked Questions
How long will a generator run on 1 gallon of gas?
Depending on the power output and load, a standard 5000-Watt generator could last anywhere from 1 and 1/2 hours to 2 hours at half of the peak load. The more the appliances connected, the faster the consumption of fuel.
Generator Fuel Consumption Chart
|FUEL TYPE||Kilowatts||Usage per hour|
|GASOLINE||5 Kilowatts||0.75 gallons|
|PROPANE||6 Kilowatts||1.42 gallons|
|DIESEL||8 Kilowatts||0.5 gallons|
|NATURAL GAS||7 Kilowatts||118 cubic feet|
How much fuel does a Generator use
A typical 5-kilowatt gasoline generator consumes fuel at the rate of 0.75 gallons per hour. The more the output power and load. Consequently, the generator will consume more fuel.
Does a generator use more gas with more things plugged in?
With more appliances plugged in, it draws more energy from the generator. Technicians refer to the plugged-in appliances as load. The more the imposed load on a generator, the more gas will be utilized quickly and will require refilling more often.
How much does a 2000-watt generator use
While running at half load, your standard 2000 Watt generator will use about 0.4 gallons of gas in 1 hour. But as with any generator, the fewer appliances connected will mean a longer time to run the generator. The opposite is also true.
How long will a 3500-watt generator run on a tank of gas?
The duration solely depends on the size of the gas tank associated with the generator. A 3500 w generator powered by gasoline running at half of the Peak load will approximately operate for 2 hours on a gallon of gas.
How long to run the generator for Maintenance?
A generator should run for at least between 15 and 30 minutes for maintenance once every week.
This is important to charge the battery and keep the electric starter working.
The best way to run your generator for maximum benefits, according to most manufacturers, is to do it at full capacity instead of running it idle.
This ensures that oil is circulated in the engine while putting it up to the operating temperature.
Whether your generator is always running or standby as back power, it requires proper maintenance.
How often you should have it serviced is determined by its model needs. Start by reading the manual to understand how to maintain your generator.
Even after calling a technician to check oil levels or replace some parts, the generator must run for a few minutes every week.
This is the only way you can ensure it will be ready and functioning when needed in a power outage.
Leaving the generator quiet for weeks will cause it to malfunction and end up with costly repairs.
Also, make sure your generator is kept in a suitable environment to remain in good condition.
A very hot, cold, or dusty can cause your generator to malfunction despite proper maintenance and the engine’s regular running.
How long can you run a Champion Generator?
Most champion generators can run 9 hours before empty their fuel tanks. In other words, most champion generators have a 9 hours runtime. However, some of them can run up to 12 hours and some others have a runtime of 8 hours. Brief, champion generators have a different runtime, it depends on what you buy.
Below are some champion generators runtime
|Brand||Model||Runtime on Gasoline|
|Champion||3500-Watt Dual fuel generator||10.5|
|Champion||3500-Watt Dual fuel generator |
(3500-Watt RV generator)
|Champion||1400-Watt Portable Generator||10|
|Champion||8000-Watt Dual fuel generator||8|
|Champion||7500-Watt Dual fuel generator||8|
How long can you run a 7500 watts champion generator?
Well, the 7500 Watts of the dual fuel generator has a run-time of 5.5 hours on propane and 8 hours on gasoline.
The Champion generator is ultra-powerful and has an electric start. It also features Dual Fuel that allows its 439 cc engine to run either on propane or gasoline.
The champion’s generator features Volt Guard, Cold Start Technology, and Intelligence, giving the generator its run-time.
This generator features a perfect integration of convenience and versatility.
The generator will work perfectly for you, no matter the needs.
It could be perfectly applicable for your next project or even your basic power needs at home.
Many people who have used this generator admit that it is one of the best power sources you can use to power your life.
The generator’s cold start technology and the convenient electric start ensures rapid starting during the cold weather.
Thus, this is the generator you could consider for a run-time of 5.5 hours on propane and 8 hours on gasoline.
Article title: How long does a generator need to cool down?
Username of writer: bellap2
How long does a generator need to cool down
A generator is made to provide power when the electricity connection is not available or an outage. However, when giving power, it heats up and requires sufficient time to cool down.
After you turn off your generator, you should allow at least two minutes to cool down. Leaving the generator to run hours on end will make it wear out fast.
The engines need some time to cool off, and during this break time, you can perform some necessary maintenance activities, including adding fuel to the gas tank.
Some generators are powered by propane or gas. When too hot, they may also blow up.
To avoid any incidences with your generator, you should ensure that the generator runs in an area that allows sufficient flow of natural air.
But even with plenty of air around, you can use the following steps to keep the generator cool:
- Keep the area above your generator open to excellent air circulation. You can have a removable top that you can remove during operations.
- Install air ventilation holes around the bottom part of the generator’s enclosure. But also make sure they are close to keeping your equipment safe during bad weather.
- When in use, always remove the cover that protects it against dust and moisture. It will increase noise, but it will keep the generator cool as it runs.
- Install fans pointing at your generator; this will increase cooling and air circulation.
A generator doesn’t take long to cook after being switched off. But it’s quite dangerous if not allowed to before being handled.
What are the conditions that should be available?
The first question has a varied answer since each generator has a different way of operation just like what the manufacturer dictated.
The size of the machine also matters. There are those that are used for prime power supply and therefore, they have large talks for fuel.
This means they can run for long periods of time even up to a week.
The second question refers to the fuel and the maintenance schedules for the machines.
There should be scheduled checks to see if the oil is out or if some important parts are wearing out.
Can a generator run 24 hours a day?
Today, generators are used everywhere, not only in industry and construction but also for domestic purposes. They can be used as a standby or constant power supply source. And the most important thing is to know how long a generator can provide electricity and to what extent. Can a generator run 24 hours a day? Of course, it can. Keep reading to find out.
Running Time of Generators
Generally, generators are not supposed to run for days. Some are designed to provide power for 8 hours, some 12 hours, while others can run for days. But you should not leave your generator to run for weeks or months. Running time depends on how the generator is designed.
If you want your generator to run for 24 hours, consider upgrading it to an industrial one. This way, you can guarantee power throughout. As much as this equipment can be handy, know that it is not designed to run continuously for days. Instead, it is supposed to run for few hours at a time.
Are There Generators That Can Operate for 24 Hours Continuously?
Many generators can’t run for fully 24 hours because of their tank size. A small tank accommodates less fuel which hinders it from operating for long hours. However, some generators can run for a whole day continuously. One such generator is Stanley 5000 Watt All-Weather Generator.
Stanley 5000 Watt All-Weather Generator
• It has a 270cc 10 hp engine with automatic low oil shutdown
• Has 5000-watt power supply, 6000 surge/peak watt
• It runs for 24 hours.
• Operates on all-weather and has a patent-pending design, four 120v gfci outlets, and removable panel
A generator can run for 24 hours a day, but it all depends on the type. A good-quality generator with a higher power supply can run 24 hours a day while a poor-quality generator can’t run for a long time.
Can a diesel generator run on natural gas?
There is no doubt that you are here to find out if a diesel generator can run on natural gas. If that sounds yes, then you are at the right destination.
Typically, many companies are developing powerful engines which can run natural gas with diesel. The technology which will allow the diesel engines to run primarily on natural gas might provide an economical way for shipping and railroad companies to shift the entire transportation to natural gas.
Advantages of shifting to natural gas
Low greenhouse gas emission; This is because the natural gas burnt emits 15 to 20% less carbon dioxide compared to diesel. Lower the cost of shipping products; On the other hand, diesel is more expensive compared to natural gas. Many companies will save a lot on energy bills. Performance; Natural gas will still provide better performance
We can agree that diesel generators can run together with natural gas. This is the technology that many companies are introducing. Natural gas comes in with many advantages compared to diesel.
The Bottom Line
There are three power sources used to run standby generators generally i.e. liquid propane or natural gas or diesel
Generally, liquid propane whole house units have an inflated quoted price.
Generators are very important to human life. It is one of the best inventions which have helped in generating power in case there is a power outage. Check out best generator deals on Amazon
However, there are things that are important to know when using generators. How long should they continuously run?