Generators For Backup Power: Natural Gas vs. Propane

Generators for backup power come in all different sizes.  There are generators for your home or your business.  They can run on different power sources – from natural gas, propane, diesel, or gasoline. Deciding which one is right for you can be overwhelming.  You must take into consideration what your needs are and how you will use it.  The type of fuel depends upon whether you can have access to diesel or gasoline or to natural gas (compressed natural gas or CNG or NG) or liquid petroleum gas commonly known as propane (LPG got shortened to LP).  An “odorant such as ethanethiol or thiophene is added so that people can easily smell the gas in case of a leak.”  When the utility power goes out at your home, there is a good chance that it went out at your local gas station, too. But if you use natural gas or propane, you won’t be standing in lines for fuel.

Back in 1910, “the New York Times reported on Dr. Snelling’s work with liquefied gas and that “…a steel bottle will carry enough [gas] to light an ordinary home for three weeks.” But do you want to light your home or do you want to live in comfort of central air and heating and have hot water for showering? The size of your home standby generator depends upon your needs and wants.

Natural gas is made up of several gases including propane, and mostly consists of methane.  Is one more energy efficient than the other?  “Which packs more power, natural gas or propane?”  The propane companies will tell you it is propane. There are comparison charts available if you would like to figure a little.  Some more complicated than others.  Many generator companies has designed formulas for their installers to use.  I have found that these may not be fully correct.  If I use their formulas, I would have underestimated which unit a homeowner would need.

I sold a 20 kW generator to a homeowner.  When I delivered the unit to the homeowner, his wife almost refused the generator. On the box, it stated that the unit was 18 KW.  She said she paid for a 20 KW.  I tried to explain that the unit she purchased was an 18 KW in natural gas or a 20 KW in propane.  It is the same unit just different fuels.  Does that affect your household and how it would run your house?  No, the unit was sized according to their needs. Is there a price difference?  Depends upon the manufacturer.  Some standby generators can be converted easily by the homeowner or installer.  Other units must come from the factory using a particular fuel.

There are conversion kits that will convert a generator from natural gas to propane or the other way around. But these kits are mostly for portable generators and not used for standby generators.  Remember, standby generators are permanently installed with an automatic transfer switch. They need a factory trained installer who is an electrician.  A factory trained dealer who is an electrician can trouble shoot a problem without blowing the board and costing you more money.

Next week in part II of this article I will tell you if there is a difference between natural gas and propane in relation to generator use.

Post your comment below.  I want to know what fuel you use and who calculated the size of your standby generator.

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Generators For Backup Power: Natural Gas vs. Propane — 6 Comments

  1. HAVE A GENTRON 3500P. I THINK I MIGHT LIKE TO CONVERT IT TO NATURAL GAS AS MY HOUSE HAS GAS HEAT. THE METER IS CLOSE TO THE BACKYARD BUT HOW HARD IS IT TO MAKE THE CONVERSION? THE MANUFACTURER CANNOT HELP ME SO THOUGHT I WOULD TRY YOU ON RECOMMENDATION OF MY SON IN CALIFORNIA WHO CONSIDERS HIMSELF MUCH MORE OF A RESEARCHER THAN HIS DAD.

    • If is is a propane unit, there is a kit that you can purchase. Check with your manufacturer first. If they don’t sell the kit then try researching online for it yourself. What kind of motor is in that unit? Look into the engine manufacturer or try researching the motor itself online.

      It is possible. It is a matter of getting smaller jets.

  2. Hello, I have an issue that I could use some help with. I have a 2007 Ford E450 Shuttle Bus that I’m having converted into a custom shaved ice bus in order to help the local schools with their fundraising efforts. With this vehicle conversion we are also installing a 10,000 to 15,000 watt generator to run the freezers, refrigerator and a couple of ice shavers. In addition to those appliances, the generator will also need to power the 2 RV roof A/C units during the summer months as well as the interior and exterior lighting and sound system. While the generator won’t need to be used while the vehicle is in motion, it will need to be on everyday and sometimes all day long with the events we will be attending. I’ve been looking for a CNG generator that we can tie the vehicle’s fuel supply with but I’m having a hard time locating a suitable generator that runs on CNG. I’ve seen a generac stand by home generator that runs on “Natural Gas” as well as several “Tri-Fuel” generators that also run on “Natural Gas” but I’m not sure if this “Natural Gas” is liquified Natural Gas or Compressed Natural Gas. I’d appreciate it if you could help me with this issue and maybe point me in the right direction.

    Thank You,

    Ron McGee

    • You should check your load. A 10 KW to 15 KW seems excessive. The A/C and heating are the usual heavy loads. LP (liquid Petroleum) gas generator is what you should be seeking for this project. A GE or a Briggs & Stratton unit can use either LP gas or Natural gas without any conversion. They contain a simple switch to chose LP or NG. Good luck!

  3. I am considering a whole house standby generator and have run cost estimates on one hour’s electric generation on natural gas vs propane and was startled by what I found. The same generator costs $138/hour to run on natural gas (Entergy) or $5.89 / hour on propane. I have not factored in the other costs such as set-up and delivery, just the fuel costs. I am wondering if this estimate seems right to those of you who have one or the other fuel source. Please reply with your actual results if available.

    • Are you sure you don’t have that backwards? In my area, the natural gas is a lot cheaper than propane. Maybe it has to do with where you live.

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