Initial use is concerned with primary purpose. Will your portable generator be used as a tool for handyman/construction work, or would it be used as a backup generator for when your house loses utility power Will it be used for your main source of power or for your remote camping site or cabin in the woods?
The needed size of the generator also will determine the economics of fuel use. Will a couple of gallons work or will you need to be hauling 10’s of gallons to meet your needs?
For commercial/construction work, you will likely have any fuel available you need and given that gasoline is a primary fuel readily available, a size-appropriate generator can be chosen easily. Any of the fuels of gasoline, propane, or diesel is really an easy choice.
This may be true also for your cabin or hunting and camping trips. Picking up a few gallons of gasoline for use as needed makes perfect sense and probably the most likely to be used.
However, if your generator is used for backup only, then you may need to be considering how much storage and how long that gasoline may remain stable. You would need to be considering if adding fuel stabilizer is a necessity to prolong life before needing to recycle your inventory.
Propane generators are mobile, but do take a little extra effort as you have to bring extra filled tanks or have access to a larger tank. Usage depends on how you expect to be able to quickly and easily obtain propane fuel or exchange tanks.
Diesel is another good fuel option as availability is excellent and it is more stable than gasoline for storage. However, most generators are noisier and may cause more of an environmental consideration depending on where it will be used. Worksites are probably not a problem, but the backyard and keeping the neighbors happy may be another consideration.
Tri-Fuel
There are a few available which will burn gasoline, natural gas, or liquid propane such as the Winco HPS12000HE Tri-Fuel Generator.
There are also a number of Impco Tri-fuel conversion kits that you can get to convert an existing gas powered generator to burn the 3 fuels.
What you need to be aware of is that the fuel BTU or energy at burn will be different for each fuel and the power generation or HP of the engine will diminish, giving you less power with propane or natural gas.
The tri-fuel option, however, gives you an advantage in long term needs of using your generator when supplies of fuel start to become scarce.
Standby Generators
In the whole house market, the non-portable standby generators are more likely going to be tied to your natural gas supply or liquid propane sources like 300 or 1000 gallon LP tanks. These are common sources of fuel in residential and commercial building. The NG/LP fuel available is likely to provide continuous, if not many days of service.
These sources provide less BTU’s and power output can be diminished compared to gas and diesel engines. Thus engine sizes get bigger than gasoline ones to put out the same amount of power.
Sure, you can get large gasoline and diesel tanks to supply this effort as well, but long term fuel stability is still a concern, and in larger applications, the diesel engines are often used because of the more stable fuel properties and the power output. Again noise levels can become a concern if the unit isn’t well isolated.
Fuel Types Pros and Cons
Gasoline is readily available, making it easy to use for day in and day out portable generator service.
Gasoline generators in the portable generator market are prolific and dominate the choices available. This is probably attributed to the abundant small engine designs that have been developed over the years as well as the vast availability of the fuel.
At 6 lbs./gallon, 2 to 5 gallons in portable cans make it easy to use and service your generator. It’s not uncommon in work environments for a service truck to have a large tank for servicing many pieces of equipment making fuel generously available.
It can be stored for a few months rather easily and prices can fluctuate significantly with demand by season based on usage levels. Long term storage requires adding fuel stabilizer as an extra cost or maintaining an inventory turnover schedule to keep it fresh.
Gas isn’t as safe as other fuels as it’s more volatile. Leaks from your containers can cause hazards as well as staining of whatever it comes in contact with. It is not the best environmental fuel with higher emissions than other fuels.
In situations such as hurricanes or other weather disasters, gasoline can become a scare commodity. If power is out, service stations may not be able to pump fuel unless they are equipped with backup generation.
You may be able to store a number of gallons for use, but if you needed a week or two of fuel, the stored fuel can become extensive. A simple example would be if you were using 5 gallons a day, you’d need to store 35 to 70 gallons to get by for one to two weeks. If you keep your car or truck full, you could use their tanks and get a few extra days if you do not need it for travel.
When considering gasoline, it’s about the expected length of time you will believe you’ll need this fuel and what impacts the fuel availability will be over the duration. In a vast majority of cases, power outages don’t last more than a few hours to a couple of days.
There are those cases where it can last many days or a couple of weeks. Take time to think about how you would manage gasoline for this service.
Liquid Propane is a common fuel. It weighs 4.2 lbs./gallon. Tanks come in the smaller 20lb (4.75 gal.) size used for gas grills, outdoor cooking stoves, with sizes from 150 gallon to above 1000 gallons for homes, cabins, and businesses. LP is stable and does not deteriorate, making it ideal for long term storage.
It becomes advantageous in standby and backup generator applications where the larger tanks are available and you can count on having long term power.
Storage of a few extra 20-pound gas grill size is good, not only for the cooking ability, but also the portable generator. It’s likely that as gasoline becomes scarce that propane may still be available and not as much in demand until more people start using up their stores for cooking.
Smaller tanks are fairly portable and using a propane portable generator is similar to a gas-powered one except connecting the fuel source takes a little more care.
LP is also the cleanest burning fuel with 30% plus or minus 10% emissions than natural gas. It does, however, produce more methane. The other downside of using LP is that it does not produce as much power per volume of use as gasoline. The offset may be in the cost, which is more stable than gasoline, but can still fluctuate with season and demand.
To consider your economics, you will need to compare typical output and use between machines:
fuel used * cost of fuel / # of hours run time at 50% load = cost / hour to run
If you take this and multiply by the number of hours expected to run per year, you’ll get a yearly cost comparison of savings or expense.
Compare both as with changing prices, this could go to benefit one or the other on economics. However, I would not make this my main consideration unless you are in a heavy use situation. Note that you may have more capital investment with propane because of the pressurized tanks.
LP will dissipate in open areas quickly making it safer than a gasoline spill; however, if it’s released in a confined space, it can be more explosive if ignited.
Natural Gas or Liquid Natural Gas (LNG) is an alternate fuel and availability is becoming more common in larger population centers for portability in tanks. It is widely available in many locations via household supply for direct connection.
Natural Gas has even a lower BTU base than propane and provides about 10% less energy production. On dual fuel LP/NG engines, you’ll get 10% less output with this fuel.
It can be easily stored for long periods in tanks similar to those used by propane. The primary advantage of natural gas is the ability to hook up directly at your home as supply will not likely be tied to power outages. This only requires a supply plumbed to your outside wall and having a connection hose to the properly equipped generator.
Again you’ll have investment in the more expense tanks for using NG unless you make the direct connection. For the direct connection, there will be some extra expense associated with the plumbing and hose connections.
Many standby generators are design to work with a direct connection to NG or LP supplies.
Diesel is also readily available, but tends to stain and attracts dirt as a heavier fuel. Since diesel is far more stable and less volatile, it can be stored longer than 10 years. There are claims of multiple decades where the fuel has been used because it was properly stored. Contamination with water is a worry, but can be addressed with Micron Filters at the tank outlet and with fuel line filtering.
Environmentally, diesel fuel is one of the cleanest burning fuels if engine setup is correct. If not, it can get heavy smoke and particulate exhaust. Diesel is also much safer than gasoline as its vapors don’t ignite as easily as gas.
Diesel is as portable as other fuels. Direct costs of the fuel have been higher recently with the new low sulfur requirements, but economics of use are better in the hours per gallon category. You can use the similar formula above as noted for LP comparison.
Summary
Essentially you need to decide on your anticipated use.
Day in and day out, a gasoline- or diesel-fueled portable generator is easily a good choice as fuel supplies are not limited and can readily be acquired.
When it comes to backup power for short durations, any of the fuels should be available in the short run. Storage of fuel long term becomes a consideration as you may need to rotate inventory for gasoline, but diesel and propane have long shelf lives and are very suited for emergency backup situation.
For propane, you can get extra tanks to run your grill and outdoor gas stoves. With diesel, you may have extra for your cars and autos if you move to a complete diesel transport model.
With both LP and natural gas systems used in houses/cabins, you can plumb your systems to be able to hook the portable or standby generators directly into a larger supply source eliminating the need for trips to the fuel depot.
You should take stock in operating conditions as well. Most quiet (smaller and inverter) generators use gasoline as the fuel source. They are economically viable and can provide basic needs for a long time on a minimum amount of fuel. These are great generators for tailgating and using in residential neighborhoods.
Of course if you want more flexibility in generation with some offset in total production, a tri-fuel generator may worth your effort, but it does require more knowledge and understanding of how to operate your generator.
Fuel is only one component of the decisions you will want to make when deciding on your portable or standby generation. It’s best that you have a broad picture of the choices, and we hope we have given you some perspective on making those choices.