How Much Propane Does a Generator Use?

how much propane does a generator use (1)

If you’re planning to use a propane generator for tackling power outages, you’ll need to know the amount of fuel it consumes. That will help you to estimate the amount of propane you need to store.

Obviously, if you choose a solar generator, you need not depend on a fuel supply. But in all other cases, the fuel plays a critical role in determining how long will a generator run.

Now, there are two main factors that determine the answer to the question- how much propane does a generator use? 

These are the

  • efficiency or fuel consumption rate of the generator and
  • the amount of load on it.

Based on these two inputs we can use a simple formula as a propane usage calculator to calculate the amount of propane the generator will need.

propane usage calculator

Propane Usage Calculator

Once you have chosen the right generator size, here’s a basic propane generator run time calculator that you can use.

Propane volume = (The per hour rate of propane consumption x working hours) + contingency hours

But this simplified formula will only work when you know the rate of fuel consumption. If that’s unknown, you can use the total running watts of the appliances you will use to calculate the propane requirement. Otherwise, you can use the rated running watts of the generator. 

Keep in mind, that you won’t run the generator at full load at all times. Usually, generators are most efficient when run at 50% of max capacity. But considering a higher wattage will give you a margin for contingency.

For that, we need to dive deeper into some numbers.

Step 1: Basic Assumptions

The first step in using this formula is to calculate the volume of propane the generator uses based on the power generated.

Let’s start with some standard assumptions.

The weight of propane is 4.24 pounds per gallon, and its approximate fuel value is around 91500 BTU per gallon

Note, fuel value is the amount of heat produced by any fuel during the process of combustion. BTU is the British Thermal Unit which is the non-metric unit for heat generated.

So, if you know the BTU per hour rating of any appliance, you can determine how long a gallon of propane will last.

For example, a 24000 BTU water heater will run for 3.81 hours on a gallon of propane (91500 ÷ 24000 = 3.81)

Step 2: Converting the watts per hour to BTUs

Now we determine the Horsepower we will need by using the following formula.

Horsepower = 1000 watts/hour ÷ 2 or 500 watts/hour. Also, 1 Horsepower = 10,000 BTUs

1 watt/hour = 1/500 horsepower = 1/500 x 10,000 BTUs 

Or, 1 watt/hour = 20 BTUs

That means, if the load is 2500 watts, you will need 5 Horsepower. (2500 x 20 / 10000)

In other words, it takes 10,000 BTUs per hour of heat from the fuel to generate energy equivalent to 1 Horsepower

So, for a load that needs 5 HP, you will need 50,000 BTU per hour.

Step 3: Converting watts per hour to the volume of propane in gallons

Once you know the number of BTUs consumed, it’s time to determine the volume of propane needed. For this, the following formula is used.

Since 1 gallon of propane = 91500 BTUs

1 BTU = 1/91500 gallons of propane

That brings us to the basic equation.

1 watt/hour= 20 BTUs = 20 x 1/91,500 gallons of propane = 1/4575 gallons of propane

That means a 2500 watts per hour load will need 1/4 gallons of propane x 2500 watts= 0.54 gallons of propane per hour

To run such a generator for 10 hours, you will need 10 x 0.54= 5.4 gallons of propane.

If you’re using a 20-gallon propane tank, then you can calculate how long it will last to run the 2500 watts per hour load.

A 20-gallon propane tank will last for 20 x 1/0.54= 37 hours

A 100-gallon propane tank would last for 100 x 1/0.54= 185 hours

A 500-gallon propane tank will last longer but the larger size and weight make it an impractical option for most users.

Obviously, the number of hours will change when the load changes.

Step 4: Converting to pounds

We already know that 1 gallon of propane = 4.24 lbs

So, 1 watt/hour = 1/4 gallons of propane = 4.24 * 1/4 lbs of propane

That means 1 watt/hour = 4.24 ÷ 4575 lbs of propane

The number of pounds of propane to run a generator for 1 hour = number of watts x 4.24 ÷ 4575

If we consider the 2500-watt generator, then the per-hour propane consumption will be 2.31 lbs each hour.

So, a 20-pound propane tank will last for 20/2.31= 8.65 hours

While calculating whole-house generator propane usage, note that a 20 lb propane tank contains about 4.6 gallons of propane. So even with a moderate power load, such a tank won’t even supply your home with backup power for a whole day.

That means to keep the generator running for multiple days, you need to store sufficient fuel that won’t run out.

Also, while calculating how much propane a generator uses, it’s best not to go by the exact numbers. Considering contingency, you should stock some extra propane cylinders.

Keep in mind, that running a portable generator continuously for 24 hours will shorten its lifespan. So, provide it with adequate rest whenever possible.

Source: Dave Hale via Flickr

How Long Will a Gas Generator Continuously Run? 

No matter whether you’re using a gas or a propane generator, it’s designed to run for a few hours at a time. The continuous running time for portable home generators can be between 6 to 12 hours depending on the model, fuel tank size, and engine performance.

In most cases, manufacturers mention the running time of a gas or diesel fuel generator based on half-load conditions.

The amount of gas consumed by a generator will depend on a number of factors. In general, a medium-size generator with d 5000-watt power capacity can consume anywhere between 0.6 and 0.8 gallons of gas per hour.

So, you can divide the fuel tank capacity by the fuel consumption rate per hour to find the running time. That said, this method won’t work on battery-powered apartment generators.

If you’re looking for continuous use, standby backup generators are a better option. Most standby generators are designed to run for extended hours. 

Note, if you cross the specified running hours mentioned by the manufacturer, you’re risking heat buildup and permanent damage to the generator.

Frequently Asked Questions

How much propane does a 20 kW generator use per hour?

A 20kWh generator produces 20000 watts of energy per hour. That means it will consume around 4.37 gallons of liquid propane per hour.

How much propane does a generator use per hour?

The amount of propane a generator uses per hour will depend on the power it is generating. To generate 1-watt hour a generator will need 1/4575 gallons of propane.

How much propane does a whole-house generator use?

The amount of propane a whole-house generator will use depends on the power being generated by it or the size of the generator. The more the power output, the higher the propane consumption.

How much propane does a 10 kW generator use per hour?

Assuming that the generator is producing 20kWh of energy, it will use 2.19 gallons of propane per hour.

How much propane does a generator use per day?

The amount of propane a typical generator will use in a day depends on the wattage and the number of hours it’s running.

Final Thoughts

Hopefully, now you have a basic idea about how much propane a generator uses. 

By using these basic equations as a propane generator run time calculator you can determine how many portable cylinders of propane you need to store.

Propane is a clean burning fuel and more environmentally friendly than gasoline. So, burning it helps in generating power in an eco-friendly manner.

Most importantly, no matter the type of fuel you use, make sure to follow all the safety guidelines while running the generator.