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.
- Easily obtained
- Portable in small containers
- Highly flammable
- Short shelf life of fuel (approximately 12 months)
- Storing large quantities of fuel is hazardous
- May not be available during power outages
- Least flammable fuel source
- Fuel easily obtained (fuel is easier to obtain during a disaster because it is a necessary fuel for the military, trucking industry, and farming operations)
- On site fuel delivery available
- Designed for off-road applications and can operate on dyed or farm/construction diesel fuel which is sold without the road tax and thus is considerably cheaper to purchase.
- Engines designed to work under a load for long periods of time and perform better when worked hard rather than operated under light loads.
- In high use situations overall long term cost of operation is much lower than gaseous GenSets.
- 18-24 month shelf life, without additives
- Installing large storage tanks raises cost of system
- May not be available during power outages.
- Engine noise is higher on a diesel compared to a gaseous engine.
- Requires clean moisture free fuel and a bit more maintenance than a comparable gaseous unit;
|Propane:**See propane notes below.
- Long shelf life
- Clean burning
- Easily stored in both large tanks or in smaller 5 – 10 gallon cylinders
- Home delivery available for larger tanks
- Quieter engine noise level
- Less expensive units with air-cooled engines are budget priced.
- Engine life for liquid-cooled 1800 RPM engines can approach 5,000 to 6,000 hours on industrial quality gaseous GenSets
- Pressurized cylinder of flammable gas
- Fuel system is more complicated (increased possibility of failure)
- Somewhat expensive fuel, check your local prices
- Propane can become very dangerous if lines are broken.
- Initial cost of generator is somewhat higher, 15 to 20% especially in sizes larger than 30 kW.
- More expensive to operate by as much as 3-times the fuel consumption compared to diesels;
- Smaller air-cooled gaseous engines are less expensive than comparable diesels but have a short life expectancy as low as 500-hours depending on engine make and use
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.
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