How To Simply Calculate a Propane Consumption For Generator: Step By Step Guide

Calculating the propane consumption for your generator is straightforward. The main thing is to know a simple formula and spend 10 minutes of your time! Read the article to the end to find out all the details.
How much propane does a generator use

Any generator owner wants to understand how much fuel his unit consumes. This is important not only to control your costs but also in cases of various emergencies, power outages, hurricanes, etc. It is logical that if you do not know how much propane your generator uses, you cannot know how much fuel you need to have in stock in case of unforeseen circumstances.

In this article, we will tell you how to correctly calculate the consumption of your propane generator per hour to know, accordingly, your consumption per day/week/month/year. Read to the end and never worry about this again!

A simple formula to calculate

Three reasons directly affect how much fuel your generator will consume:

  1. The model of the generator and its efficiency, which is measured in BTU/hour;
  2. The load on the generator (how much energy do you get from it);
  3. How long you’re running the generator each day.

To understand how much propane you need to store, you first need to calculate how much fuel your generator uses per hour. We multiply the flow per hour by the number of hours you plan to use the generator and add a few hours in case of emergencies. In total, our calculation will look like this:

Propane use = propane consumption per hour x working hours + a few hours just in case of emergency.

This simple formula will help solve any problem associated with calculating your fuel consumption. So let’s start by counting per hour.

How to calculate how much propane a generator uses per hour step by step?

How to calculate how much propane a generator uses per hour step by step?
  1. Firstly, we need to assume the average efficiency of the typical generator.

It is measured in BTUs and indicated on the generator. Here we are talking about basic information that concerns the average generator and already starting from this we propose a formula further. In the likeness of this formula, each person will calculate his own expense.

We know that a 2 horsepower generator typically produces about 1000 watts of electrical power. It takes 10,000 BTUs of fuel per hour to produce 1 horsepower of mechanical energy. Propane has a fuel value of 92,000 BTU per gallon and weighs 4.2 pounds per gallon.

  1. Secondly, we need to calculate how much horsepower we are using:
Horsepower = (W / 1000) x 2

For example, if you have a base load of 3000 watts, you would need 6 horsepower. If the nameplate of your generator shows only amps and voltage, the wattage can be estimated by multiplying volts times amps to calculate watts. So amps times volts equals watts, which is our load. 

  1. Thirdly, we need to know the ratio to BTU.
BTU = horsepower x 10,000

In our example above, the 3000-watt load would consume fuel which produces 60,000 BTU per hour.

  1. Finally, we can find out how much propane this corresponds to:
Gallons of propane = BTU / 92000

Therefore, running a generator with a 3000-watt load for an hour would consume (60,000 / 92,000) or 0.65 gallons of propane.

  1. We combine all calculations into an equation:
Propane used per hour (gallons) = (watts / 3000) x 0.65

0.65 gallons of propane weigh approximately 2.73 pounds. A 20-pound propane cylinder will contain 20/2.73 x 0.65 = 4.76 gallons. You could run a 3000-watt load off your generator for around 7 hours.

Please note, that all these calculations are approximate and you should always take into account the different efficiency of individual generators. Either way, this simple calculation formula will help you figure out your fuel consumption. This will be a nice starting point for determining how much propane your generator will consume in an hour, week, month, or whatever time interval you need. Remember, it’s always best to have extra fuel just in case.

Using a cylinder or a tank: what is the difference?

Most portable generators connect to a 20-pound propane tank that holds 4.7 gallons of propane when filled. The above calculations lead us to believe that it is unlikely that a single cylinder will be able to provide an entire house with energy even for a day unless you are extremely economical in using energy.

So if you want to power your home for a few days, you will need several cylinders or a propane tank in place. Please note that connecting to a tank is not as easy as using portable cylinders, you will still have to shut down the generator for installation and maintenance.

However, the tank will also help extend the life of your generator if you don’t use it 24/7 non-stop. In this case, you must decide which is more convenient for you to use for a few days: a couple of cylinders or one tank, but with a little tricky installation.

What is the best fuel to choose for a generator?

What is the best fuel to choose for a generator?

To choose the right fuel for your generator, it is worth considering to what extent and in what area you are going to use the generator, your lifestyle in general, the expectation of fuel costs, etc. We will talk about the pros and cons of the four main fuels, and the choice remains after you. If you don’t want to choose one energy source, you can always give your heart to the best dual fuel generator.

🔥 Gasoline

Most portable generators run on gasoline, as it is quite convenient — thanks to local gas stations, it is easy to get. Also, many gasoline generators can provide a lot of energy even with half a tank of fuel. Among the disadvantages — gasoline is highly flammable, so it is unsafe to store it in large quantities.

💡 Diesel

Diesel generators are commonly used in industry, as diesel is the best fuel for working in remote areas or extreme climates. Diesel provides an efficient fuel-to-power ratio. Such generators are easier to maintain than gasoline generators and are also designed for more intensive use. These generators are reliable in emergencies and can even run on old or low-quality fuel. Cons: they are quite noisy and also create emissions, affecting air quality.

🔌 Propane

Many people choose liquid propane as a fuel for their generator, as they can choose portable models or stationary ones for business and home. Propane is a more environmentally friendly fuel and has a long shelf life. Of the minuses, what we talked about above: due to the limited capacity of the cylinder, you may need two or three spare propane cylinders.

💎 Natural Gas

If you need a constant power supply for your home, natural gas is the best option. The main advantage is that the natural gas lines will work even during a power outage. Also, the price of natural gas is much lower compared to other fuels. Disadvantages — natural gas is not available in some areas of the United States (San Francisco, Seattle, Denver, New York). Moreover, a generator powered by natural gas will not be as efficient as other fuels.


It’s always nice to be sure that your home can always get enough energy. To make this your reality, you need to know at least the approximate consumption of your generator to be able to replenish your stocks on time. With a simple calculation, you can always know the propane usage for your specific generator, without worrying about emergencies.


⏳ How long will a 20 lb propane tank run a generator?

Generator run time is directly related to how heavy the load is. Since generators consume two to three pounds of propane per hour on average, a generator can run for about five hours with 20 pounds of propane.

⌚ How long will a generator run on 30 lbs of propane?

A generator with a 30 lb tank will run for about seven hours at half load as well.

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

If you have a 7 kW generator, it will run 66 hours, and if you have a 12 kW generator, it will run 36 hours on a 100-gallon tank at full load.

🕝 How long will a 500-gallon propane tank run a generator?

If you have a 500-gallon tank, which can only be filled to 400 gallons, then a full tank would last you around 6 to 7 days.

💰 How much does it cost to fill a 500-gallon propane tank?

Depending on the market price of propane, the cost can range from $600 and up to fill a 500-gallon propane tank.

  1. Thanks for the great article! I was always wrong and bought not enough fuel for the generator and had to buy at the most inconvenient moment.

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