How Much Propane Does a Generator Use?

n some parts of the world, power outages are much more common than in others. In fact, due to natural calamities, many states in America are prone to similar circumstances. It is best to come up with safe and eco-friendly alternatives, such as investing in a propane-powered generator to avoid any inconveniences during unwanted situations. 

Buying Propane-Based Generators

Propane is a form of liquefied petroleum gas or LPG. For many households, especially those that prefer a clean-burning fuel, reliable source, and efficient energy consumption, propane is a popular choice of energy source. 

According to Rufus Youngblood, Director of Safety for Ferrellgas, propane generators produce over 12% less carbon dioxide and 20% less nitrous oxide than their natural gas counterparts, which results in an 80% reduction in smog produced due to using generators. Other than that, there are many different benefits of a propane-powered generator, which include: 

  • Provision of twice the energy per cubic foot, once compared to natural gas. 
  • Safe and Long shelf life. Unlike diesel or gasoline tanks, propane storage containers have safety valves to prevent spillage.
  • Easy maintenance of generators compared to gas generators.
  • No carbon deposits or residues are left in the generator’s engine, exhaust, or fuel lines making propane a cleaner-burning fuel.
  • No added stabilizers are required. Propane can be stored for longer durations without any stabilizers, unlike gasoline.
  • Easy re-fills and readily available exchanges are offered at local markets and nearest gasoline stations. It is readily available even in case of natural disasters causing interruption of electricity, unlike gasoline.
  • Leakage does not pose a hazard to the environment. 

When buying a generator for household consumption, one has a lot of questions in mind. However, the most asked question includes how much propane a generator uses on average.

This is a pertinent question that comes up if you are planning to go for propane, diesel, or gasoline generators to correctly plan the storage requirements. You are, of course, spared this trouble if you are hooked up to any of the natural gas lines that allow you access to large quantities of fuel to run your individual generators for as long as you like.

While it is best to consult an experienced technician to answer most of your questions, figuring out the consumption rate of propane is a pretty straightforward matter to solve on your own. 

So, How Much Propane Does A Generator Use? 

If you are opting for a generator that runs solely on propane, you need to know how much fuel a generator uses to properly weigh out your costs. Regardless of what estimate generator retailers give you, the truth surrounding propane’s usage is directly related to a variety of factors, which include: 

  • The size of the generator.
  • Overall power usage and load on the generator. 
  • Duration the generator is run.
  • Generator model, Generator efficiency, and Condition of the generator.

Now, let’s review these important factors to help you budget your propane usage correctly. Plus, knowing how much propane is going to be used by your generator comes in handy in situations where you might be expecting power outages for days. 

What Size Generator Do You Own? 

Regardless of the company and brand, the size of a generator can be determined by its wattage or kilowatt rating. Kilowatt is the unit to help assess the output power delivered and, consequently, fuel consumption.

Generally speaking, a generator that delivers more kilowatts, will be bigger in size and consume more fuel. Its full tank of propane is going to last for a much lesser duration. Knowing this rule can help you estimate how much propane you require for your respective household with respect to your generator’s size.

If you are still in the process of finalizing the generator size for your house, you may read our generator sizing guide here. The size of the generator is governed by factors such as

  1. You want to power your entire house or selective partial loads during a power outage. How much propane a whole house generator use will depend on the total connected load of your house.
  2. What is the maximum starting wattage demand on your generator in addition to the running wattage?

Still unsure? Let’s make it even simpler for you. According to U.S. Energy Information Administration (EIA), an average American household uses approximately 6-kW, or 6000 watts of energy during a power outage, which includes a standard refrigerator, a few light bulbs, and a laptop. 

However, if you plan on supporting an entire air-conditioning unit, a water heater, a sump pump, and all of the light bulbs in your house, you might be looking at an upward of 6-kW, possibly going up to 10-kW.

Overall Power Usage and Load

Propane usage is directly dependent on the actual load connected and the actual power delivered by the generator. You might have selected a higher size generator but run it with much lower connected loads. Your fuel consumption will be higher than a properly sized generator based on your loads but substantially lower than when you run it at full load.

Any appliance with higher power consumption will require more fuel supply.

Duration of Generator Use

How many hours you run a generator directly affects how much fuel it will consume. A whole house generator run continuously will definitely consume more fuel than most portable generators used only during a power outage.

Generator Model, Generator Efficiency, and Condition of the generator.

Generators with higher efficiency ratings will consume much less fuel to deliver the same amount of energy in comparison to the less efficient ones. Age and number of hours the generator has run have a direct impact on the condition of parts, that corrode and wear out with time and operation. New generators will consume less fuel than any older model of the same rating.

Calculating Propane Gas Usage 

Every household’s consumption is different. Now that you’re familiar with the propane consumption of a standard American family, you need to calculate how much propane your generator will use, given your specific household requirements. 

For this, we recommend calculating propane usage through two different models, both of which are as follows: 

Model A: Simpler Calculations for Propane Storage 

If you are new to owning generators, it is helpful to know that storing propane will always be handy, especially in emergencies or natural disasters. However, it is not always easy to know how much propane you need to stock up at all times, especially if you are someone that likes to budget and be wary of costs. 

The following equation can help you decide the right amount of propane storage required as per your specific household’s consumption:

Total Propane = (Propane use per hour x hours) + Contingency

To calculate the total propane usage for storage purposes, we need to have some basic assumptions regarding the efficiency of a typical generator and the properties of propane, which are as follows: 

  1. Propane-powered generators of 1 horsepower ratings require 10,000 BTU per hour propane under load.
  2. Propane has a weight of about 4.2 pounds per gallon. So a 500-gallon tank will weigh around 2100 pounds.
  3. Propane has a fuel value of about 92,000 BTU per gallon.
  4. A two-horsepower generator will produce approximately 1000 Watt back up power output at full load.

Step #1) Calculating how much horsepower is consumed:

Horsepower (HP) = [watts (W) / 1,000] x 2 

where HP is the horsepower of the generator and W is the wattage of the electrical load fed.

In order to feed a 2,000 Watt maximum electrical load, your generator must use 4 HP.

Step #2) Calculating BTU per hour required by the load:

BTU per hour Required = horsepower x 10,000

The 4 Hp propane-powered generator will consume fuel that generates 40,000 BTU per hr.

Step #3) Calculating how many gallon propane is required per hr:

Gallons of propane per hr = BTU per hr / 92000

Gallons of required propane per hour for 2000 watt electrical load = 40000 / 92000 = 0.43 gallon propane per hour

Step #4) Calculating the size of the propane tank required: 

Total Propane Required = Gallons of propane per hr x No. of hours of storage planned.

For a 24-hour period of fuel consumption, propane required = 0.43 x 24 = 10.43 gallons

You can fill your liquid propane tank only up to 80% capacity.

So, Size of propane tank required = 10.43 x 1.25 = 13 gallon tank.

Here, it is important to note the following considerations: 

  • On average, a 20-pound propane cylinder can run a 3000-watt load for approximately 6 hours. 
  • Knowing these calculations can help you figure out your propane storage easily. 

Model B: Realistic Calculations for Propane Usage 

Regardless of how many calculations you may draw for proper propane storage, in reality, you might run out of fuel. Hence, we always recommend having a few pounds over the amount you have calculated. This is because the amount of load being drawn by your generator is not always consistent. 

It could be that your base load of appliances is given; comprising of the equipment that you will run throughout the day. Peak load comprises the devices that your generators run only for a certain duration in a day. For example, when most of your devices and lighting are running, you might experience a higher load during the evening. This can result in more power being drawn by your generator, and consequently, more watts being utilized. 

As a result, your contingency is increased. Although the same steps are followed in both cases, the calculation equation changes just a bit. Hence, the following equation is used instead for a more accurate estimation: 

Total propane = [(propane use per hour base load) x hours] + [(propane use per hour peak load) x hours] + contingency

Step #1) Calculate [(propane use per hour base load) x hours]

  • Calculate Horsepower, BTU, and propane of base load hour, as given in Model 1. 
  • Estimate total propane used per hour with the base load. 

Step #2) Calculate [(propane use per hour peak load) x hours]

  • Calculate Horsepower, BTU, and propane of peak load hour.
  • Estimate total propane used per hour. 

NOTE: *Peak load hour is when most of your appliances are being used at the same time. For example, between 4 to 8 pm, when you are using the dishwasher, the washing machine, the microwave, the stove, and the television.

Step #3) Calculate [Step 1 + Step 2] + contingency

  • Add answers from both the steps, along with contingency.
  • The answer gives you the total propane used.

Knowing how to calculate both the models gives you a reasonable estimate of how much propane does a generator use on average, as well as how much propane you need to always store at home.

Being well versed with these assessments can, without a doubt, help you save a lot of money and be well prepared during an unwanted crisis. So, always try to remember these two equations in assisting you when it comes to saving time, money, and resources. 

Size of Propane Tanks 

Another essential aspect to note when weighing out how many gallons of propane you need to have on standby essentially surrounds the size of the propane gallon tank you have available at hand. There are various sizes of propane tanks available in the local market, ranging anywhere from 20-pounds to 100-pounds. Any weight over that, however, requires connections with special propane contractors. 

If you experience occasional power outages that last no longer than a day, you can easily rely on a 20-pound propane generator tank. This type of propane tank is known as a grill cylinder and holds about 5 gallons of propane. Each gallon of propane weighs about 4.2 pounds. The grill cylinder may weigh somewhere between 15 to 17 pounds when empty. 

So a propane-powered generator with a 20-pound cylinder can provide enough power only for part of the day and you may need multiple such fuel cylinders if the outages are for longer durations.

However, if your respective area is prone to power outages experienced every other day, you might need a larger propane tank to sustainably carry the load of your appliances. In such cases, a 100-pound propane generator tank may do the trick.

With an average running time of about 70 hours or more, a 100-pound propane tank can efficiently operate a 7-kW generator at 75% capacity. Similarly, if you’re looking to run your generator for over a week or more, we recommend investing in an even larger gallon, say, a 500-pound or 1000-pound propane generator tank. 

If you require smaller tanks, such as grill cylinder tanks that hold between 20-pounds to 50-pounds of propane, you can easily find them available for re-fills and exchange at various stores at your local market. 

However, you might need to contact a propane distributor if you want larger propane tanks, such as those that hold between 500-pounds to 1000-pound propane. This is because such heavy re-fills are not readily available at the local markets. 

Conclusion

Now that you are familiar with the workings of propane generators and how much propane does a generator use, it is time for you to get to work! Grab your keys and make your way to the nearest supermarket to buy your desired amount of propane gallons. 

Last but not least, be sure to calculate propane storage and usage, according to your household’s consumption, prior to purchasing the gallons to ensure that you are never short on propane when it comes to powering your house. 

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