How Much Propane Does A Generator Use?

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Propane usage in generators infographicI get asked about propane generators for home use quite often. Most people who have this question want to know how much it might cost them to run a propane powered generator at their home.

This is a very good question because there are some significant advantages to using these devices but there are also some disadvantages that you should probably know about.

Are Propane Generators Fuel Efficient?

Unfortunately, as a general rule, propane generators aren’t quite as efficient as their gasoline or diesel powered cousins. The reason that they might use more fuel than other types of generators is simply a matter of physics. The amount of energy that propane is capable of producing when it burns is simply less than both diesel or gasoline.

How Efficient is a Propane Generator?

According to Wikipedia, propane is capable of producing 84,300 BTU’s per gallon, gasoline is capable of producing 114,000 BTU’s per gallon, and diesel is capable of producing 129,500 BTU’s per gallon.

This basically means that 1 gallon of propane only produces 74% of the energy that 1 gallon of gasoline can produce or 65% of the energy that 1 gallon of diesel can produce. If we’re just looking at the math, based on the energy output of propane alone, you would need 26% more propane to do the same amount of work as 1 gallon of gasoline. Similarly you would need 35% more propane to do the same amount of work as 1 gallon of diesel.

In simple terms, based upon the laws of physics, you should expect to go through more propane than you would gasoline or diesel in similarly sized engines.

How Long Can a Propane Generator Run?

This is simply a function of how large of a tank you have and how large the engine is. If you only have a very small 20 pound propane tank like those that are commonly found on many barbecue grills, your generator won’t be able to run nearly as long as it would if you had a larger tank.

What Size Propane Tank For Standby Generator?

I wish I could answer this question in the kind of detail that I would like to but it really depends upon the size of generator that you plan to run. For example, if I were to convert my small Honda EU2000i generator to run on propane, I could get by with a 20 or 30 pound tank. If, however, you would like to power a very large standby generator for your home with propane, you will need a much larger tank. Each generator will be different because they will have different engine sizes. You will need to check the documentation for the particular generator that you would like to power with propane to find out exactly what size of tank you’ll need.

One thing to keep in mind is that propane is in a liquid form while it is in a compressed storage tank but it can’t be used by a generator in a liquid state. It needs to vaporize into a gas in order for it to be able to combust in an engine that is powering a generator. If the generator has a very large engine, it will have a much larger appetite for propane than a small one would. In order for a propane tank to satisfy the appetite of a large engine, the liquid propane would need to be able to vaporize inside the tank fast enough to meet the demands of the engine. Because of this, very large propane tanks are often required for very large propane generators.

2-11-2012 Update: I’ve recently learned that some generators are actually capable of drawing liquid propane from the tank and then converting it to a gas before it enters the engine.

Are Propane Generators Loud?

Some people claim that propane generators are quieter than gasoline powered generators. It’s not the type of fuel that determines how loud a generator will be. There are many factors that determine how loud a generator will ultimately be. Saying that all propane generators are either louder or quieter than other types of engines is a blanket statement that simply can’t be made.

It’s possible for a propane generator to be quieter than a gas generator but it has nothing to do with the fact that the generator is running on propane. It has much more to do with the way the particular generator has been designed.

If you are interested in reading about some very quiet types of generators I suggest that you read my article called: What is The Quietest Generator For Camping?

How Do Propane Generators Work?

These types of gensets work basically the same as any other type of generator. The only exception is that instead of using a traditional carburetor they often have specialized carburetors that are designed especially for burning propane. In other cases, they have carburetors that have been converted to run on propane.

Another difference is that instead of pouring fuel into a gas or diesel holding tank, you will connect a hose coming from the propane tank to the generator. Other than that, they basically worked the same as any other type. The propane is simply another type of fuel that powers an internal combustion engine. As the engine turns the generator head it produces electricity. This is the same regardless of the type of fuel that is used to power the engine.

Are Propane Generators Safe?

Some things about propane generators make them safer but some things may also make them more dangerous. For example, there’s no need to handle gasoline or diesel when refueling them but there is a risk of fire or explosion if the fuel line that connects the propane tank to the generator is punctured.

Even with propane generators, it’s important to precisely follow the instructions that are provided in the owner’s manual to make sure that you are following all safety precautions. Additionally, you should never use a propane powered generator (or any other generator) indoors.

Can A Propane Generator Run On Natural Gas?

This really depends upon the type of generator that you have. There are some generators that are designed to run on multiple types of fuel. There are even some tri-fuel generators out there that are designed to run on gasoline, propane, or natural gas. It is not possible, however, to simply connect a natural gas supply line to a unit that is designed to run on propane and expect that it will work.

Are Propane Generators Good For Off The Grid Use?

Now let me take a minute and tell you some of the good points about propane generators. Some of the advantages to owning this particular type of a genset are listed below.

  • Propane is a much cleaner burning fuel then either diesel or gasoline so it is better for the environment.
  • Because propane burns cleaner, it is less likely to leave harsh carbon deposits in the engine which may increase the life of the engine and reduce maintenance costs.
  • Propane lasts much longer when stored than either diesel or gasoline which means that it is an ideal fuel for standby or backup generators.
  • Propane can be stored in larger volumes than a typical homeowner would be able to store the other types of fuels. For example, at our off grid cabin we have a 300 gallon outdoor tank and the propane to fill it is delivered by a local company.

How Long Does A Propane Generator Last?

As with all mechanical devices, the lifespan of this type of a generator really depends on several factors. One is how well the device is manufactured. Another is how well the engine on the genset is maintained. Yet another is how often the generator is used. If it is only used occasionally, one of these generators will probably last for many years. If it is used every single day and not maintained well, you can expect it to break down much sooner.

It’s impossible to tell you exactly how long a propane generator will last because there are just too many factors involved. One thing that I can tell you is that since a propane generator burns cleaner, there will be less carbon deposits in the engine which could lead to a longer lifespan of the engine.

How Much Do Propane Generators Cost?

Again, this depends heavily upon the particular generator that you intend on purchasing. As a general rule, the propane generators that I’ve priced tend to be a little bit higher than a similarly sized gasoline powered generator. Many generators that are designed to run on propane are specialty units that are capable of powering an entire home in the event of a power outage. These gensets will likely be water cooled which will add to the cost of the unit. Asking the question, “how much does a propane generator cost” is like asking how much do cars cost. There’s no one answer.

What’s The Bottom Line?

To summarize this article, you know now that propane doesn’t produce as much energy as gasoline or diesel when it is burned so gallon per gallon it is not likely to be as efficient as these other types of generators. That being said, there are some definite advantages to using a propane generator and I mentioned those above.

The advantage that stands out most to me is the fact that it is a clean burning fuel so using this type of a power generating device at you’re off the grid home would mean that you are not releasing as many harmful emissions into our planet’s atmosphere.

I hope you found this article to be both helpful and entertaining. If you did, you can do me a big favorite and help to spread the word about by clicking on either the Facebook like or the Tweet button located just below the title of this article. Thanks for stopping by and I hope to see you here again real soon.

If you’re looking for a quite running generator, I suggest that you read this article: How to Quiet a Generator.

12 Responses to “How Much Propane Does A Generator Use?”

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  1. Mike says:

    In your “whats the bottom line” column, you might consider putting the average cost per gallon for propane as compared to the cost of other fuels. This cost (which is anywhere from a dollar to two dollars per gallon) makes up the difference for the fuel being less efficient and thus gives propane the advantage being that it burns cleaner.

  2. Matt Hill says:

    Nice job. I am purchasing one in the next couple of weeks and I’ve spent about 8 hours learning about them. You summerized what I learned in those 8 hours in one unbiased article that I wish I saw a few hours ago.

    • Patty Hahne says:

      Thanks Matt!

  3. Bedford Brown says:

    My question is the sane as above. can a 20 pound propane tank be used in an emergency to supply a 15kw generator.

  4. Norma Carpenter says:

    We have a 100 propane tank and I want to get a 11000 btu generac and my husband says that will last only about a day and we will need a bigger tank. Does this sound right?

    • Patty Hahne says:

      I’m not sure Norma. I suggest that you call a company that sells propane generators to get an idea of run time in relationship to the size of your tank.

    • Ken says:

      A 11k btu Generac will likely have a B&S engine between 500cc and 600cc, give or take. That size engine tends to use 1 gal/hr on half a load and as much as 2 gal/hr on a full load. A 100lb tank, only has about 23 gallons of LP, I believe. so, your husband is right, at half load, it’d be used up in a day.

  5. Jeff says:

    If my generator is only 100cc(3 HP),2000 watt- gasoline, but conv to lp.
    With a 100lb tank
    How many hours/days could it run for?

  6. Michael Stafford says:

    Will propane generators be able to be set for methane as are many trucks. And cars .I believe you only need 550 BTUs….for it to do so. IS this possible for a generator

    • Jim Wilson says:

      Some gensets are designed for propane or natural gas (methane) and can be
      setup for either but not both. Most larger “house sized” units fit this category. Small size units generally are designed for only one fuel or the other.

      Propane and natural gas devices operate at slightly different pressure and flow characteristics.

      Your installer can make the needed changes..

  7. keith says:

    I was burning 10-12 gallons of gasoline a day with an 8500 watt generator running loaded up. The math says:

    12 x 1.26 = ~15 gallons of propane per day (for my situation)

  8. Chuck says:

    Does anyone have an opinion (or, better yet, information) about kits for converting between gasoline and propane? I’m thinking about buying a Champion 3500W generator.

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