How long can a generator run?

Generators can be used for many things, from powering RVs and worksites to functioning as a source of backup power during an outage. In some cases, they can even be used to power a worksite or home that is off the electrical grid. Whatever the case, you’ll be asking the same question: “How long can a generator run?”

The answer depends on a number of factors, but the most important is the generator’s fuel consumption. Generators that consume fuel quickly will have a shorter runtime than generators that consume fuel more slowly. The tank size, fuel source, and generator type must also be taken into account. Larger generators, especially standby generators, tend to run longer than small portable generators.

On average, you can expect a gasoline-powered portable generator to run about 7.5 to 12 hours continuously, a propane-powered portable generator to run for up to 8 days if continually refueled, and a standby natural gas generator to run continuously for up to 3 weeks. Exact numbers will vary. To learn more about your specific power needs, try using AlltimePower’s free Power Calculator. You’ll find out the ideal size of your future generator and how much you can expect to pay.

Portable gasoline generators

Most portable generators on the market are powered by gasoline. These types of generators are often very affordable and easy to transport. However, they often have a short runtime compared to other types of generators. On average, a gasoline-powered portable generator will run for 7.5 to 12 hours, though some models can run for close to 24 hours.

This may be plenty of time if you are running a generator at a campsite or worksite. If you plan on using the generator as a backup source of power during outages, however, you risk running out of fuel before the power comes back on. Look for models that last for longer, such as the Westinghouse WGen3600v, which can run for 18 hours. The Briggs & Stratton 30676, which has a runtime of 14 hours at half load, is also a good option.

If you want to make your gasoline-powered generator last longer, you may be tempted to refill it while it is running. This would be a mistake. Generators heat up while they are running, and gasoline fumes could be ignited by the heat and cause a fire. Instead, you should always let the generator cool down completely before refueling it.

Estimating runtime for gas-powered generators

It’s difficult to calculate a gasoline-powered generator’s exact runtime because it will vary based on load. A generator’s load refers to how much power the generator produces, and it varies based on what appliances it is powering. A generator at half load will last longer than a generator at full load. While it’s usually not possible to calculate a generator’s exact run time, you can estimate it.

To estimate a generator’s runtime, divide the generator’s fuel capacity by its fuel consumption rate. Assuming you start with a full tank of gas, this equation gives you the generator’s maximum runtime. The generator dealer should give you the model’s fuel capacity and fuel consumption rate. If not, you can estimate these numbers based on comparable models and sizes.

In some cases, the generator dealer will give you a generator’s estimated runtime, eliminating the need for the equation. It’s also possible to determine runtime by simply timing how long it takes your generator to power through a tank of gasoline. This will likely give you a more exact understanding of your generator’s runtime, but it may mean wasting a tank of gasoline and a few hours of your time.

Portable propane generators

Unlike gasoline generators, propane generators can be made to last longer than a single container of fuel. The best way to do this is by using a propane gas regulator. This device will allow you to connect two propane tanks to a single gas line. Once two tanks are hooked up, turn on the flow from one tank while leaving the other closed. When that tank nears empty, twist a valve to switch the fuel source to the other tank.

If you continually switch out the old tank for a new one, you can continue this process for days. The limiting factor for this method is the amount of oil in the generator’s engine. If the generator had plenty of oil when it started running, it could last up to 200 hours, which is just over 8 days. Most newer generator models automatically switch off when oil levels run low, so you may not even have to worry about keeping track of oil levels yourself. Just remember to add oil after running your generator for extended periods of time.

The last factor you’ll need to consider is heat build-up. If you run your generator for more than 24 hours at a time, you’ll need to pay attention to how hot your generator is getting. When the engine gets too hot, you risk causing permanent damage. Try using a fan to cool the engine down while it’s running, or even consider packing the generator with ice. If nothing else works, you may need to turn off your generator now and then for a few hours to let it cool down.

Standby generators

Standby generators are larger and more expensive than portable generators, and they are usually fixed to the ground. Because they are designed for the purpose of backup power during outages, they can usually run continuously for longer than portable generators.

Like gasoline generators, diesel-powered standby generators are limited by the size of the tank; however, they usually have a larger tank and thus can run for more hours. Many diesel generators have a 24-hour tank, but you can also find diesel generators that last 48 or 72 hours. Before refueling a diesel generator, turn it off for a few hours to let it cool down.

Natural gas generators are connected to a home’s natural gas lines, so in theory, they can run indefinitely. Most generator manufacturers, however, recommend that you run a generator for a maximum of 500 hours at a time, or just shy of 21 days. This will give you a chance to check oil and coolant levels and let the generator cool down. While running a generator for extended periods of time, you should check on it every so often to make sure it’s not overheating or malfunctioning.

Solar power

Fuel-powered generators are not your only choice when it comes to backup power. Recently, some homeowners have invested in solar power. Solar panels can be connected to either a solar generator – usually a portable one, which comes with its own solar panels – or a backup battery system, which can be connected to solar panels on a home’s roof.

The amount of energy a solar generator can store is measured in watt-hours (Wh). How long the generator lasts also depends on how much power the appliances need. For example, if a mini-fridge requires 1,000Wh but an LED light requires only 100Wh, a 1,000Wh solar generator could power the mini-fridge for an hour or the LED light for 10 hours. Overall, however, solar generators do not provide as much power as fuel-powered generators.

Backup battery systems, on the other hand, can sometimes last indefinitely if you use solar energy during the day and store up excess energy to use at night. You may, however, have to limit the amount of energy you use to make sure you have enough. On especially cloudy days, you might run out of electricity. Depending on the size of the battery and the amount of energy you need to use, it will typically hold 3 to 12 hours’ worth of power.

Continuous power generators

Though most generators on the market can only run continuously for so long, there are some generators that are designed to run indefinitely. These types of generators are generally bought by people who want to live off the grid. They are also useful at commercial sites where power lines don’t reach, such as certain mining and oil and gas operations.

Continuous power generators are designed with heavy-duty materials that can handle heavy loads without needing repairs. They also use a specialized cooling system with cold water jackets to prevent the engine from overheating. Because they run continuously, they don’t usually last as long as standby generators and may need to be replaced every few years. This, combined with the cost of fuel and the heavy-duty design, often makes running continuous power generators an expensive endeavor.

Before you decide what kind of generator to buy, you should understand your energy needs. To avoid overloading or underutilizing your generator, calculate how much power you’ll need it to produce. You can calculate this by hand by looking up the starting wattage of every appliance you want to use, or you can use an online calculator such as AlltimePower’s generator sizing calculator. We’ll also give you the option to be matched with reputable generator dealers in your area.

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