## Propane-Powered Generators: Are They the Best Choice?

Recently I was asked the following question by someone who wants to install a 5000-watt generator to run their home in case of a power failure:

What is the best choice for fuel, propane, gasoline or diesel?

This reader is leaning towards getting a propane-powered generator. The choices are confusing, and a guide like this one can help the newcomer to the world of generators make the best choice.

I have been doing some research on the subject and here are some of the advantages and disadvantages of all three fuels for generators: gasoline, diesel, and propane.

Propane produces 92,000 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 means that it will take more propane per hour that either gasoline or diesel to run a generator.

How much propane will my generator burn per hour?

• It requires 2 horsepower to produce 1000 watts of energy per hour under load
• Under load each horsepower consumes 10000 BTU per hour
• Propane contains 92,000 BTU per gallon
• Propane weights 4.2 pounds per gallon

Using these factors how long can a 5000-watt generator run on a 500 gallon propane tank at 50 capacity.

• 10 horse power at 50% would use 5 HP to generate 2500 watts of electricity
• 5HP X 10,000 BTU would consume 50,000 BTU per hour
• 500 gallons X 92,000 = 46,000,000 BTU of energy in a full 500 gallon tank
• 46,000,000 BTU divided by 50,000 BTU = 920
• A 500-gallon tank that is full would run a 500-watt generator at ½ capacity for 920 hours.

After comparing the various fuels, I would probably go with propane for a large generator in a fixed setting. I would want a minimum of a 1000 gallon tank. For small generators I would go with a tri-fuel generator. Tri-fuel generators burn propane, gasoline and natural gas.

If you choose to purchase a large generator you need to weight the cost versus the benefits. Is running a generator worth the cost? Another consideration is how much fuel you are able to store. Propane tanks store indefinitely, which is another reason the propane generator is a good choice.

Howard

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### 33 Responses to Propane-Powered Generators: Are They the Best Choice?

1. TimV says:

Howard, what a great topic.

If someone asks “what kind of generator should I get?” would it be better, as the consultant, to start by looking at it from owner ability and mindset? Is the person’s skill level exhausted when swiping the card at the hardware store and loading up the cardboard box? If they are clueless about basic maintenance, especially with an engine that does not have an oil filter, maybe they should plan on buying several generators and bake that into the equation.

Does the person demand to retain their current standard of living while on backup power? I know plenty of people who like to turn on five or six hundred-watt lights when they get home “just to have some light”. Maybe in a short term event this can be accommodated by throwing money at fuel. Long term, and that person will have failed (why do people/groups fail article) because they are too entrenched in their beliefs about reality to roll with the punches, and their generator selection “became irrelevant”.

If you are talking VERY long term, once propane is gone, it’s gone forever. If a situation is getting bad, do you think the person that drives the propane truck will be out and about in what amounts to an unarmed Brinks truck full of gold? Murphy will be close by, and the event will happen before you can get the tank refilled after a few years of monthly system exercises. If it is a propane conversion, you can fall back to burn gasoline, but did the person stop thinking about the prep when the shiny silver propane tank was set and filled? Propane – check. Done! Next!

This might be true for any sort of prep, using a decision matrix that starts well before questions about fuel type. Are you clueless? Go to A. Can you change your own oil? Go to B. etc., then work down to short term or long term, budget, etc. As an example at the clueless end of the spectrum, someone asked me to go with them to “the glock store” to help them pick something out. I know this person zones out in a stressful situation, is functionally useless for the duration, and has a standard urban home with so many easy entry points that it might as well be a screen house. My litmus suggestion was to put a bar on the door. Scowl (that won’t look good). There are some people that can’t be helped, and the consultant must decide when to say “There is nothing I can do for you.”

As an aside, I traded for a 200 gallon Diesel tank that had 10 or 15 gallons sloshing around in the bottom (below the totally rusted pickup tube). It had not been used in Who Knows How Long. The diesel that drained out before getting to the gunk burned just fine in the old tractor.

Your points are well, that is the reason that I am always telling people to take it out of the box and use. There is a learning curve to almost everything and yes there are some people you can’t help.
Howard

• Dave says:

I considered a natural gas emergency generator, for the whole house…good, convenient, automatically comes on when power goes off…but EXPENSIVE, somewhere around 5, 6000 dollars!

• Noah says:

Yeah, the expense is pretty high and most people can find a lot of other uses for the money.

• Mich says:

“once propane is gone, it’s gone forever”
…Have you considered using the wood-gas? I suppose that once all my pb supplies are gone I’d be able to feed the generator with wood-gass (maily methan).

2. Lew says:

We had a hotel in a remote area for a few years and ran a 135kva diesel generator as our power supply. To lower the running cost we ran the engine (Cummins 6 cyl C series )on 50/50 LPG and Diesel fuel mix. The introduction of diesel was simply via a hose inserted into the inlet air intake, when the engine was started you simply open the gas supply and increase until the governor dropped back to about half way, when the engine needed to compensate for extra load the engines governor increased/decreased to supply while the gas supply remained static. We had a 2000 liter tank of LPG. Apart from the saving the engine oil never went black.

• Ranchdude says:

That’s very interesting, and good to know in a pinch. But wasn’t LP gas just as hard to get in a remote area as the diesel would be? And just as expensive, if not more so, than diesel?

3. TR says:

You cannot get 1000 gallons of propane in a 1000 gallon tank.

They only fill it to 80% because of pressure and the fact that you need the empty space for propane gas to be drawn off the liquid propane (LP).

You also cannot run a generator off the last 20% or so of a propane tank because it will not deliver sufficient pressure.

A 1000 gallon tank will be filled at max to 800 gallons or so, and will not be able to fuel the generator with the last 200 gallons.

This means that you will really only be able to count on 60% of the rated capacity, more or less, or 600 gallons.

Hope that helps.

Tr You are right in that they will only fill a propane tank to 80%, how ever you can run a propane tank much lower then 20% although they don’t recommend it. Howard

• Ranchdude says:

“You can’t run generator off the last 20% of the tank” is a very subjective statement. That may hold true for very small tanks, but not very large tanks. Smaller tanks get cold as the gas vaporizes and expands, and it’s the lower temperature that impacts the vapor pressure. A larger tank can be run to a much lower percentage of the total, especially in warm weather because a larger tank has more surface area to create the pressure, and it’s also a larger thermal mass which won’t cool as much.

4. Randy says:

Sigh, good points but some are not accurate. My diesel is (very) quiet, very low maintenance (like most, not requiring major maintenance for 30,000 hours)and, by far the most efficient over other fuel types (using .42 gallons/hour at 10KW). When treated the fuel stores for 10 years plus.

Please note: What I’m talking about is a liquid cooled, 1800 rpm genset. Not one of those air cooled 3600 rpm versions. By far, diesel is the most energy dense fuel.

My maintenance over the 6000 hours I’ve placed on the unit has been two fuel filters and an annual oil change every year.

Now the catch. They’re more expensive up front. But in my experience, worth every penny. I tried the “explode in 500 hours” gas types and got tired of it.

Save and buy a diesel unit. You won’t regret it.

• Anonymous says:

What make and model generator

5. AThomas says:

About two years ago I had a Generac 20K “Whole House” generator installed, along with a dedicated 1000 gallon propane tank. The tank is buried and can hold 90% capacity underground (due to the cooler, more stable temperature). I never heard about the loss of pressure when down to 20%, so I’m glad I stumbled into this article.

The generator has kicked on a few times, for several hour power outages over the last couple of years. It’s worked flawlessly and fairly quiet. I don’t hear it from inside the house, except when I’m in a room directly on the other side of the wall from it.

The electrician that installed the generator said that the newer Generac models are far more reliable than past ones, so I’m keeping my fingers crossed that it out-lives me (He wasn’t a Generac salesman).

The Generator cost about \$7500 installed, and the 1000 gallon propane tank was about \$3500 installed. 900 gallons of propane at \$1.70 a gallon adds another \$1530. Pretty pricey to keep the house powered….

Is it worth it? I dunno.. But I’m glad I did it.

I do keep a portable Honda 6.5k (one of the super quiet ones) handy, as well as 60 gallons of gasoline that I slowly rotate through, throughout the year. It’s easy to rotate fuel, between mowing equipment and vehicles. Just make sure you label it with a date, because it’s easy to forget when you filled up the cans.

6. David says:

What about solar? Any good ones that don’t break the bank?

7. Olivia Sherwin says:

This is some great information, and I appreciate your point that propane generators are less expensive. I want to invest in a generator to have as a backup in case of an emergency, but I wasn’t sure what kind I wanted. I’ll definitely look into a propane one for its lower price. Thanks for the great post!

8. Alvan Atkinson says:

Live on farm so off road diesel is our fuel of choice. If nat gas then this might be fuel of choice. Propane if live in woods. Gasoline works for small generator, rotate fuel with stabilizer on yearly basis. Have done this for 20years without problem. If very cold propane may not vaporize is tank above ground. Small generator, want automatic, get standard Briggs-Honeywell or Generac. Automatic transfer switches for large generators-large price. Many variables. Well pump long outages go to diesel, nat gas. Frequent short, automatic propane.

9. Thanks for sharing this thought. It’s maybe less expensive than others but personally, I suggest to use dual fuel generator for long durability. I own a 7000w of champion generation.

Ha ha @Mich already said “once propane is gone, it’s gone forever”.

10. Could someone please discuss a emp protected solar generator? Thank you

11. John McCluskey says:

Will any this work after an EMP? Is anything EMP-proof?

• Ranchdude says:

Sure, just install and run it in a Faraday cage with output /input protection.

• buba says:

lol no body will be here to know :O

12. Steve says:

Hello I have a food truck and I Ned over 50 amps generator propene with tow 50 amps outlet what generetor. Name I have to by ;;??

13. Bob Canning says:

I work at http://www.EastIdahoProperty.com. When we sell a house in Idaho, I am often asked about back up power because the power goes out here at least with two or three times a year. One thing to think about with propane is the temperature. Propane tanks are great in warm climates. But when you have -5 or -15° weather, the efficiency of propane drops as the tanks ability to deliver propane decreases. Having a tank that is correctly sized and buried can help Around here, natural gas is a great alternative. Of course it cannot be stored. Diesel can also be a problem because of the low temperatures. Diesel generators need heaters to keep the fuel from jelling. So when people are deciding on what kind of generator to get, they also need to take into consideration the climate.

14. F. R. says:

Another choice to keep in mind is a generator that can run off of a choice of fuels. The Duramax 10000 (rated 4.5 stars by purchasers) we bought recently can use either propane or gas, so that would help a lot with the issue of running out of one type of fuel. Like most people, I realize one can only count on a generator for short term, as no processed fuel supply supply would be available for long in the event of a real catastrophe. Or woodstove will always be our #1 “survival” tool!

• Chris says:

We also have had a Duromax 10K dual fuel,auto idle,electric and pull start and it has been working flawlessly for two years now.Runs the entire house,including the well pump and furnace with no strain at all. Dependable machine, especially for the money. Definitely recommend it.

15. My brother is currently having a house built for his family up in the hills. He wants to have a generator installed in case the electricity goes out, but he’s not sure which type to choose. I didn’t realize propane gas generators are able to run for 920 hours at half capacity with a 500 gallon tank. I’ll be sure to share this information with my brother.

16. Power grid goes out. You live in rural are with well for water supply. Electricity goes down, no water. Can someone tell me what type generator would be necessary to run well pump? Appreciate your thoughts

• Noah says:

A manual well pump, like the Bison pumps, are by far better than relying on a generator. In the scenario you mention, fuel of all types will be in short supply, and when you run out, your generator will be useless. Invest in a manual pump and that won’t ever be a concern.

17. Art says:

I owned a Propane-powered backup generator in Florida. When I bought it the price was the same as for the gas version, just had to order the right one. BTW, the propane version put out 15% more power. I had a 500-gallon propane tank (buried) that ran the generator, stove top and flash hot water heater. I had to put about 100 gallons of propane in the tank every 2 years. The generator ran 20 minutes every week for maintenance.

18. Vince Alarid says:

Art
What size propane generator did you buy ?

19. Edgar Bowen says:

Regarding propane fueled whole house backup generators, I would like to suggest the following, which I am very glad a friend suggested to me prior to my purchase.

After receiving my crated 20K Generac generator, I was ready to have the local propane company sell me a package which went something like this:

We will supply you with a “free” 500 gal. propane tank, hook it up to your generator … (which I already had wired into the house w/ transfer switch and all).

We will work out for you a very attractive discounted price… We will charge you only for the materials to hook your generator up to the propane tank … and of course the price of the propane in the tank.

Anytime you need a fill-up, call us, unless you opt to go with our automatic “top-off” service, in which case you will NEVER be low on propane.

What they failed to mention was that since “the free tank” really belonged to them, THEY WERE THE ONLY COMPANY AUTHORIZED TO FILL IT (AT THEIR PRICE) … A very bad deal!

On good advice, I PURCHASED the tank from them and paid them to install it.

I now buy my propane from whoever has it at the lower price.

20. keith says:

Your math is fine but the assumptions are wrong. A 500 gallon propane tank can only be filled to about 80% capacity. So 400 gallons

21. Roberto Marquez says:

Having just escaped from the hurricane in PR I have to say that, unquestionably, you need to go with propane. You need the generator in an emergency, and as anyone who lives in Florida or PR can tell you, then IT hits the fan, gas can be hard or impossible to get. Natural gas lines can also be affected by a severe storm, so counting on a steady supply of natural gas is a risky proposition, even assuming you do have that service at home. Propane may turn out to be somewhat more expensive, but take it from someone who just went through the hell of Maria: when you are without energy, you don’t care about cost. You don’t want to wake up one day after a storm and realize that your generator ran out of gas and you can’t get any gas anywhere, and you could have bought a propane generator but decided against it because it would cost you 5 bucks more per day. Your wife and kids would dismember you.