Duromax XP4400EH Dual Fuel Model
Dual Fuel Generators and even the less common Tri Fuel Generator are becoming more popular if only for their versatility. One unavailable fuel source in an emergency allows you to still use your generator with the alternate fuel.
When all sources of fuel are available to you, it becomes a matter of choice based on the many variables, not the least of which is initial cost of the generator and operating cost of your fuel choices.
There are safety concerns as well as environmental impact to consider as well. So where do you start? What are your choices? Dual Fuel? Tri Fuel? First you must understand the pros and cons of the different types of fuel.
Your Fuel Choices
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There are four main fuel choices to run a portable generator. They are:
- Gasoline
- Diesel
- Liquid Propane (LP)
- Natural Gas (NG)
Typically, portable generators are manufactured to run on a single fuel. There are popular models that are termed dual fuel portable generators, or bi fuel which can be run on gasoline or liquid propane. A tri fuel generator is made to run on gasoline or liquid propane or natural gas.
Gasoline and diesel are commonly available at your local service station. Liquid propane is what you use to fire up your back yard barbeque. Natural gas can come to you through your local utility company and you may be cooking your meals or heating your water with it.
Is a Dual Fuel Generator For Me?
In deciding if a dual fuel or tri fuel portable generator is for you, first become familiar with the different fuels. There are pros and cons of each fuel type. This article will describe the different fuel types. Once you understand the benefits or drawbacks of each, you’ll be able to decide which fuel source is best for you, and whether a dual or trifuel generator is for you.
Of course you would expect that a gen-set that allows you that option would cost more. They do, but perhaps not as much as you might expect. For example, the very popular DuroMax XP4400E 4,400 Watt and the XP4400EH (pictured above) differ only in that the latter can run on either gasoline or liquid propane. The cost difference is approximately $100 more for the dual fuel model. Even when you get up into the 10kW versions, the difference is still just above $100, so it doesn’t depend on the output as much as it does the hardware.
You might be interested in the cost difference between gasoline powered and liquid propane powered generators. Generac, one of the leaders in portable generators makes a 5500 watt model 5939 (GP5500) which runs only on gasoline and a 5500 watt model 6001 (LP5500) which runs only on liquid propane. The LP model runs just about $100 more than its gasoline counterpart.
Generac 6001 LP5500 Liquid Propane Model
Generators that run on diesel are the most expensive. You should expect to pay two to three times more for a diesel generator over a similarly powered gasoline or vapor gas unit for the same power and features.
Since the diesel engine (compression/ignition) differs from the engine that will utilize a vaporized fuel/air mixture in the other three fuels, there is a separate article on this site devoted to the portable diesel generator. As a rule of thumb, diesel is the choice (because of its engine) for when you want to work your engine at or near its full capacity for long periods of time. The diesel engine is more fuel efficient when used as a workhorse. Diesel as a fuel source will be described here as a comparison fuel type.
Brief Descriptions of Fuel Types
There are two other forms of diesel available which have their benefits. Bio-Diesel is a cleaner-burning diesel replacement fuel made from natural, renewable sources such as new and used vegetable oils and animal fats. You can mix 20% Bio-Diesel with your conventional diesel without engine modification, and provide the same energy with less emission. Emulsified diesel is mixed with a small percentage of water and an agent that keeps the water and diesel mixed.
LP and NG are basically interchangeable with some slight alterations. Since LP is under higher pressure, the orifice delivering the gas for NG use must be larger. In addition, the regulator that controls the amount of fuel injected into the engine is different. There are propane generator conversion kits that you can buy to turn your gasoline generator into a LP generator, or your LP into NG.
Natural gas is a mixture of hydrocarbons, mainly methane (CH4), and is produced either from gas wells or in conjunction with crude oil production. This is the gas that many households already use.
There are two types of propane delivery. Vapor propane delivery draws the fuel from the top of the tank usually through a pressure regulator at the tank. The liquid in the lower part of the tank must be able to absorb sufficient heat from the tank surroundings for vaporization to take place. The liquid propane (common to portable generators) draws the liquid from the bottom of the tank. High pressure tubing carries it to a device to vaporize the fuel before combustion.
OK, ready?
For purposes of this article, I will be assuming portable generators below 10kW (10,000 watts). Since standby generators are in fixed locations, their use of natural gas or large storage tanks of diesel or liquid propane are most commonly used.
Following are factors that I think you should consider when looking at how these fuels will work for your situation.
Engine Cost and Durability
By far the most popular fuel source in portable generators is gasoline. Probably because they are much cheaper to make (and purchase) than their diesel cousins and to some degree their propane alternatives.
Aurora 6500 watt Diesel Generator
Diesel engines, because of the way that they utilize fuel, are the most durable. They are the choice for running at full capacity for extended periods for this reason. And they need less maintenance. In fact, maintenance for a diesel is pretty much limited to regular oil changes. Although the oil used must be rated for diesel engines.
Just look at the recommended maintenance for non-diesel engines. Maintenance includes not only oil changes, but periodic replacement of spark-plugs, air-cleaner, ignition points, rotors, distributor caps and plug wires. And the occasional carburetor adjustments and tune-ups.
Diesel engines normally run at 1800 RPM (half that of gas engines 3600 RPM) and can last 20,000 hours with regular maintenance. LP engines can last as few as 5,000 hours. There are diesel generator engines that are designed to run at 3600RPM. Their lifespan is accordingly much shorter in the 10,000 to 15,000 hour range with proper maintenance.
So for periodic or emergency use, gas or propane generators make the most sense. For heavy extended use, life expectancy of a diesel fueled generator can make up the added expense in the long run.
LP, being a more complex system increases the possibility of component failure, making for possibly the shortest life span. In general, LP should be considered the shortest durability.
Fuel Efficiency and Cost
The winner in fuel efficiency is diesel. Diesel fuel has a higher energy density than gasoline. Just a bit of common sense shows this. Diesel engines get more miles per gallon in a vehicle. It is the obvious choice for long haul truckers, farm and industrial equipment, and anywhere the most energy for the money is needed. Therefore in the long run, diesel generators are the least expensive to operate.
As far as gasoline vs propane prices, you know gasoline prices fluctuate all over the board. So does LP to a lesser extent. Consider this when choosing.
Champion Duel Fuel Generator Model 71531
For comparison purposes, you can look at the Champion dual fuel generator model 71531 (7500 running watts). It will run 9 hours on 6 gallons of gasoline and 9 hours on 5 gallons LP at ½ load. You’ll need to compare fuel prices at the time. That’s a clear advantage of a dual fuel portable generator. You can run the less expensive fuel by your choice, assuming both are available.
It’s interesting to note that in the Champion 71531 model, the unit is rated for 7500 running watts with gasoline and 6750 running watts when run on liquid propane. Most models claim the same wattage regardless of the fuel type run.
Natural gas can be the least efficient fuel with 30% less BTU’s that gasoline. This means that the energy density is the least of the alternatives, however natural gas can be the least expensive fuel.
Fuel Storage and Availability
Gasoline is readily available through your local station, as can be diesel. LP tanks are also available at gas stations as well as other locations in the common 5 gallon tanks. NG is often piped directly into your neighborhood and into your homes.
500 gallon propane storage tank
During a power outage, you might not be able to get gasoline. It takes electricity to pump gas, not to mention high demand for what could be a limited supply. You can simply purchase LP in tanks during power outages. NG would also be available in a power outage. If the outage was due to an earthquake, NG is a poor choice and may not even be available.
You might have storage tanks for diesel or LP on your property. If so, you can have local delivery of that fuel. The cost of the tanks if you don’t have one should be considered in the overall cost of setting up a generator system.
Gasoline has a short shelf life of several months without adding fuel stabilizer. Diesel has up to 24 months shelf life. LP has the longest shelf life and can easily be stored in 5 or 10 gallon tanks. However, portable storage containers for LP (pressurized tanks) are more expensive than gas containers. Storing large quantities of gasoline compared to large tanks of LP or diesel is hazardous.
NG does not need to be stored, but it will not be available in many areas.
Safety Considerations
Flammability is a safety concern that can’t be avoided. The other main safety consideration is the by-product carbon monoxide produced in all cases.
Gasoline vapors are highly flammable. Diesel has little volatile vapors. Diesel fuel is heavier and oilier. It evaporates much more slowly than gasoline. Gasoline vapors are emitted at room temperature, whereas diesel has a boiling point above that of water.
Diesel fuel evaporates more slowly because it is heavier. It contains longer carbon chains than gasoline does (gasoline is typically C9H20, while diesel fuel is typically C14H30).
Diesel is the least flammable fuel of our considerations. In both gasoline and diesel, you have spill risks.
LP is a flammable liquid in a pressurized tank! That’s a double whammy. Leaks from the tank or its hose system are of definite concern.
Carbon monoxide is produced by an internal combustion engine. It is a colorless, odorless gas that is fatal over even short exposure. This safety concern is preventable with proper use of your portable generator. Every year, hundreds of portable generator users are killed by this toxic gas by not observing proper ventilation during operation.
Gasoline produces the most carbon monoxide. LP or NG less and diesel the least.
Green Considerations
We’ve all know the adverse effects of gasoline burning engines on the environment. The LP or NG choices are the cleanest burning generators with the least greenhouse effect in their emissions. They are the most compliant in emission regulations.
Diesel produces the least carbon monoxide, hydrocarbons, and carbon dioxide. We hear that these are the culprits in global warming and depletion of the ozone layer. However, diesel produces nitrogen compounds and soot (particulate matter). This soot can lead to acid rain and smog.
As for noise pollution, diesel is the loudest. LP NG are the quietest. But after all, they’re generators. They’re loud. If it’s quiet you want, go with an inverter type generator.
Location and Portability
Portable Generators are meant to go with you
These are portable generators. You expect to be able to use them when and where you need them and not have them in a permanent location. Gasoline generators are the most portable, another reason for their popularity. The tank is attached so no need to cart around a propane tank with you. Both gasoline and propane generators are lighter and less bulky than their diesel counterparts.
NG generators limit their portability. You’ll have to know where the gas lines are available and have the ability to connect to it wherever you go. Therefor transportation from location to location is out of the question.
Depending on where you need your generator to operate, temperature could be a concern. In extreme cold, gasoline or diesel will fare better than the gasses. LP can be hard to start in low temperatures, especially if you are relying on vapor propane. Natural gas can degrade at low temperature.
Summary
So which fuel type is the best? Well that depends on the factors that make it the best for you! I know you might not like that answer, but at the generator grader I pride myself in education. My choice may be different than yours. But in my opinion, for periodic use or in emergencies, the versatility of a dual fuel model is worth the additional cost.
Filed under: Articles • Dual Fuel
We just ordered a westinghouse WGen9500 gas powered generator. for a slightly less price we could get the same generator but dual fuel with gas/propane. we have tim to change the order before it is shipped out. Should we switch to the bi-fuel or keep the gas?
Please answer ASAP.
Hi Irene,
The dual fuel (bi-fuel) option is more versatile and should be decided upon by your preference, availability of fuel, fire danger, etc. Consider if operating fuel cost is a factor for you. In portability, you’ll have to move a tank wherever you move the generator. I think the result is important either way. Power when you need it, when you need it. Good luck and stay safe.
Ray
If you can exchange do so. For me it was well worth the xtra for dual fuel gas/propane. When you need electricity and the gas stations are packed or out of gas you can generally find propane.