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How Long Will a 20 LB Propane Tank Run a Generator?

Generators are essential when you need to keep an emergency supply of energy for your home, particularly if your area often experiences power outages due to a lack of power supply or because of disasters. Knowing how long a propane tank will run the generator is important.

A 20-pound propane tank will run a generator for a total of about five hours. A propane tank of this size can usually carry around 4.6 gallons of propane. So, depending on the total weight of your load of propane, the operating times may vary.

Please read on for further details and answers to common questions people have on this topic.

Photo courtesy of Quiet Hut

How Much Propane Does a Generator Use Every Hour?

In general, every hour, generators will consume around two to three pounds of propane as they function. And with a heftier propane load, the operating times will decrease accordingly.

How to Easily Compute How Much Propane It Will Take to Run a Typical Generator

If you’re wondering how much propane you will need to run your generator and want to do the computations yourself, here is an easy formula that you can use down below so that you can make an estimate calculation yourself:

FORMULA: Total amount of propane used in an hour (in gallons) = watts / 3000 x 0.65

This is the formula used for a 3000-watt generator. Let’s break it down bit by bit to understand further how this formula can be used to compute your total consumption of propane.

Part 1:

Before we get started, let’s do some basic assumptions for the average generator using the following numbers down below:

On average, two horsepower generators are able to create 1000 watts of electricity. Next, 10000 BTUs of fuel are required to generate just one horsepower. Moreover, we should also consider that the fuel value of propane is 92000 BTU every gallon and that the weight of propane every gallon is 4.2 pounds.

With this in mind, we should note down the following numbers to use in our calculations.

Part 2:

First, we need to find out how much horsepower we’re utilizing using this formula:

Horsepower = (wattage / 1000) x 2

With a generator using 3000 watts, you would require a total of 6 horsepower.

Part 3:

Next, we can simply multiply our calculated horsepower to this formula in order to get the BTU ratio we need as part of our computation:

BTU = calculated horsepower x 10000

In the second step, we ended up calculating a total of 6 horsepower. Insert this into the formula above, and we get a total of 60000 BTU hourly.

Part 4:

Lastly, we can now compute the amount of propane this results to down below with the following formula:

Gallons of propane = BTU / 92000

We previously computed 60000 BTU in the third part, so let’s insert that into the formula. In the end, we can see that operating a generator with 3000-wattage would have an hourly consumption of 0.65 gallons of propane.

Combining it all into one formula, we result in the formula written above. So, 0.65 gallons of propane equates to a weight of around 2.73 pounds. This is solved by multiplying 0.65 pounds with 4.2, which is considered the weight of one gallon of propane.

Next, we will now see that a 20-pound propane tank comprises a total of 4.76 gallons, and it can be confirmed using the following equation: 20 divided by 2.73, multiplied by 0.65, which equates to 4.76 gallons. With this, we can come to the conclusion that a generator with a total of 3000 load wattage can operate for 7.32 hours.

As previously stated, the wattage used above is for a generator with 3000 watts. For reference, here’s a quick guide as to how long will a 4000-watt, 5000-watt, 7500-watt, and 10000-watt typical generator run on propane down below.

Again, it should be noted that these are just rough estimates based on your average generator and don’t actually consider other varieties of generators out there. Nevertheless, using the formula above will provide you with a good start and estimation of the amount of propane that your average generator requires.

Related How Much Does It Cost to Fill a 20 LB Propane Tank?

How to Choose the Best Propane Tank Size for Your Generator

To operate your generator efficiently, you must select the correct propane tank size for your generator by basing it on the size of your generator and the total amount of time in which you’ll keep your generator running.

Your purchased generator should come with instructions and details regarding its propane consumption per hour. In addition, you may also contact the producer of your purchased generator for this information and if you happen to have other concerns.

Next, you should decide how long you want your generator to operate and supply electricity into your home. As previously stated, a 20-pound propane tank on a generator will run for a total of five hours. That is enough to power up your gas stove, furnace, and any other small appliance that doesn’t require a lot of energy to operate. And with their size, you can easily store multiple 20-pound propane tanks for your disposal.

For longer outages, you may need a larger amount of propane. For instance, a 100-pound tank of propane loaded on your average 7000-watt generator can run for a little over two days. However, using the same amount of propane but with a generator utilizing a bigger wattage, such as 12000 watts, will last you for only one and a half days, lessening the amount of time your generator can operate.

To fully power your home with a generator, you’d generally need a 20000-watt generator with a 500-gallon tank. That will last you a maximum of six days. Such a generator would need 400 gallons of propane to operate for that long.

If you decide to keep your generator as an emergency supply, you can calculate the amount of propane that you’ll need to run your generator for a certain amount of time.

Related How Many Gallons of Propane Are in a Tank (With Size Chart).

Do I Need to Purchase a Generator?

A man pulls the starter cord to start the generator

Depending on your circumstances, your situation might call for a backup or an emergency supply for your electricity as needed. If you’re still unsure if you need a generator purchased and installed on your home, here are some of those factors that can help you decide if you do need a generator. Here they are:

1. If you frequently experience power outages in your area

If you live in an area where power outages frequently occur, purchasing a generator is an ideal backup for electrical supply.

Especially if you experience outages and live in colder climates, you will need a backup supply for electricity to power up your heater and other necessities that require electricity.

2. If power takes a while to restore in your area when you experience outages

While power outages may be resolved in a few hours for other areas after a storm and such, those living in distant areas could go for days or, worst, experience weeks without any electrical supply.

Because of this, you must get yourselves a decent generator that will last you for a while and can at least power up the necessities in your home as you wait for the electricity in your area to be restored.

3. Emergency concerns

Emergency concerns such as medical reasons may urge you to get a generator as soon as possible, especially when you have a family member reliant on medical equipment that needs to be powered by electricity to operate.

Even if power outages don’t frequent your area, a sudden one can put that family member’s life at risk, so, ideally, you get yourself an emergency electrical backup just in case.

4. Portability and storage of your generator

If you decide to own a generator, you will need to place it in an area where you can easily set it up and fit it in your house. In addition, you also have to ensure that it’s placed far enough and is stored in a well-ventilated area to avoid your family from getting sick due to carbon monoxide.

For instance, you can store your generators in your garage or any other storage room available in your house. Lacking the space needed to store your generators properly will compromise the safety and health of your family.

Related How to Run a Generator in the Rain (And Not Ruin It).

How to Choose the Best Generator for Your Home

When choosing the best generator for your home, it’s best to purchase one that will best suit your needs and budget. Now that we’ve discussed the various factors that can help you decide if you need a generator for your home, you should consider your budget and know the perfect generator for your home based on your needs.

1. Choosing your preferred type of generator

When choosing an emergency backup for power supplies, there are various generator types that you can choose from. Other than home standby generators, here are other generators that other people also look into for other options:

  • Portable generators: These generators are much more affordable than home standby generators, as the most expensive ones usually only price up to $2500. However, the highest wattage that these generators offer is only up to 8500 watts.
  • Inverter generators: Because of their complexity in usage, these generators are way more costly compared to other generators. One perk they can offer, however, is their ability to function quietly and efficiently. In addition, they also create lesser emissions.

But ideally, home standby generators are still preferred as they can utilize propane gas, unlike portable and large inverter generators. Propane gas, after all, is less harmful to store.

Besides the reason above, propane gas can also be stored for extended periods, unlike gasoline, due to its long shelf life. So, you can store multiple quantities of propane gas without worrying about them deteriorating in the long run. In addition, they are also much more preferred since they are a clean-burning fuel.

One downside that you may see in home standby generators is how costly they can get. Other than their high price, they also need to be professionally installed. Not including the installation fees, standby generator prices usually start at $4000.

But when power outages hit, these generators can automatically start up and provide more power than other types of generators. Moreover, these generators usually offer 5000 watts up to 20000 watts.

2. Make a list of all the appliances you want to power up during emergencies

What will you need to run during outages? These should be the essentials, such as your heating system, refrigerator, lighting, and the like. And as previously mentioned, do you need electricity for other appliances in your home, such as medical equipment you may need? Be sure to take all of this into consideration.

When trying to find out the respective wattages of certain appliances at home, you can look at the labels of your appliances for reference. If you want to be extra sure about it, you can also look for reliable guides online.

3. Calculating the total wattage for the generator size you need

A 7000-watt generator can power up at least the essentials at your home, such as your refrigerator, heating system, lighting, and the like. With a full-load 100-gallon tank, your 7000-watt generator will continue to function for around 66 hours. In addition, the greater the wattage, the lesser time your generator will run.

So, it is important to get yourself a good-sized generator with the corresponding wattage you need to utilize your power supply properly. More importantly, if you live in disaster-prone areas, there are more reasons to invest in a bigger generator.

Furthermore, it’s recommended that you purchase a generator that just somewhat exceeds your computed wattage. After all, you’re better off having those excess watts over a generator that ends up overloading.

Wrapping Up

Cartoon Propane Tank Running

When choosing a generator to use as a backup, it’s ideal to go for home standby generators powered by propane fuel. After all, propane can be stored for longer periods and can still be usable even after then.

It’s also important to know the suitable generator for your home by listing which appliances you’ll need to run with your generator during such outages, and make sure to pick the correct propane tank size that will fit your generator accordingly.

Lastly, you can make estimated calculations of your total wattages using the provided formulas to properly utilize your generator and your propane tank.

For more, check out Should You Open Propane Tank Valve All the Way?