How long will a 120 gallon propane tank run a generator?

Many people today are not running generators solely for emergency purposes. In addition to home use, generators are being used in remote locations to power everything from tools/equipment to camp sites. Knowing the amount of propane the generator may use is helpful so you can be sure to have enough on hand.

The amount of propane that a generator uses will be based on the weight of the load, or watts of power being drawn. 

Typically, a generator will use between two and three pounds of propane per hour when run at full load. 

20-pound vs 100-pound Propane Generator Tanks

A 20-pound tank, which holds approximately 4.6 gallons of propane, will run an average of four to five hours. The 20-pound tank, also known as a grill cylinder, weighs about 17 pounds when empty. The terms pounds and gallons are often interchanged when referring to propane tanks. Knowing the difference can avoid confusion. Tanks are referred to by the pound. Propane is sold by the gallon. Propane weighs 4.6 pounds per gallon.

A 100-pound tank can run a 7-kilowatt generator for 66 hours, or a 12-kilowatt generator for 36 hours. In general, generators operate between 25-75% of their capacity, so the fuel supply may last longer. A 100-pound propane tank holds approximately 23.6 gallons.

Twenty- and thirty-gallon portable propane tanks are readily available for exchange at many stores or can be refilled at propane distributors. Larger propane tanks (100 to 5000 pound) are usually delivered by a propane distributor, are fixed in place, and their trucks will deliver refills.

To estimate the amount of propane that your generator may use, it is helpful to understand how much power is being drawn. Generators are rated based on kilowatts of power. Every appliance has a rating of average watts per hour of use. One thousand watts of energy is equal to one kilowatt, which is abbreviated as kW.

An example of kilowatt hours used to power conservative use in an average size home is 5-kW to 7-kW (5,000 to 7,000 watts). This would power a few lights, a refrigerator, and a laptop during a power outage. If you needed to also power a full air-conditioning unit, a large freezer, and a water heater, the kW use would be greater.

To determine the size of the generator you need, follow the link to see a worksheet of average watt use for various appliances

Is Propane more Eco-Friendly than Gas?

Propane generators are more eco-friendly than gas/diesel. They emit 12 percent less c02 (carbon dioxide) emissions, 20 percent less NOx (nitrous oxide) emissions, and produce 80-percent less smog producing hydrocarbon emissions. Unlike gas/diesel, propane is cleaner burning and does not degrade with time.

According to Rufus Youngblood, Director of Safety for Ferrellgas and a member of the technical committee for the NFPA 59 (Utility LP-Gas Plant Code), “If the propane container and valve are in good shape, storing propane for 10-30 years or more shouldn’t be a problem.” Check your local/state guidelines for acceptable use dates on portable tanks. Many will not refill tanks older than ten years.

FAQ

How many pounds of propane are in a gallon?

Propane weighs 4.24 pounds per gallon. A 20-pound tank, therefore, holds approximately 4.6 gallons of propane.

How long will a 20-pound propane tank run a generator?

On average, generators use between two and three pounds of propane per hour. A generator can run an average of one-two hours at moderate load on a 20-pound (4.6 pounds) tank.

How long will a 100-pound propane tank run a generator?

On average, generators use between two and three pounds of propane per hour. Depending on the kilowatt use, a 100-pound tank fueling a 3-kW generator can run an average of 96 hours, a 7-kW generator can run an average of 66 hours, or a 12-kW generator for 36 hours.

How much propane does a whole house generator use?

Depending on the energy draw and the size of your generator, you may use around 2-3 gallons/hour. Using a 20-kW generator and a 500-gallon tank, which holds approximately 400 gallons of propane, then a full tank would last you around five to six days.

What is the difference between a propane generator and gas-powered generator?

Gas and diesel-powered generators are commonly found in portable styles as their maximum kilowatt output is 8,500 watts of power. Propane generators are often put to use in more fixed situations, i.e. homes, businesses, as they can begin at 15,000 watts.

Gas and diesel-powered generators require monitoring of the fuel as it tends to degrade with time. If not used regularly, the fuel can gel and break-down in the engine requiring mechanical care.
Propane has a long-life and does not degrade, so intermittent use does not affect the engine. Propane has a higher octane-rating, so combined with its low carbon and low oil-contamination characteristics, delivers improved engine life.

Typically, a duel fuel generator will be noisier than a propane generator. If maintaining a calm and quiet atmosphere is a priority, propane might be your best bet.

If you’d like to lower the sound coming from your generator, look at building a generator quiet box.

Is it cheaper to run a generator on gas/diesel or propane?

Gasoline generators typically cost much less to purchase and to install. Gas generators also put out more heat than propane, about 30 percent more for the same amount of fuel. It is important to have proper venting and circulation for any generator. 

Propane generally costs less per gallon than diesel or gasoline, as it has a lower density. Propane generators are less efficient than gas generators, producing fewer BTU’s per gallon of fuel. A gallon of propane has 27% less energy than a gallon of gasoline. However, propane is a cleaner-burning fuel than gasoline, making it better for both the environment and your generator.

The initial cost of a propane generator may seem high, but in the long run it could be a bargain. It can generate enough power to operate a home and often has many smart features (auto-start) in the event of a power outage.

How long will 120 gallons of propane last for generator?

How long will a whole house generator run on 100 gallons of propane?

How long will 250 gallons of propane last on a whole house generator?

How long will a 100lb propane tank run a generator?