What Generator Fuel Type is Best? Compare Your Options

If you are shopping for a portable electric generator and have stopped to consider fuel options other than gasoline, you may feel somewhat overwhelmed by options. Although there is some overlap with multi-fuel systems (more on that later), there are four main portable generator fuel types: gasoline, propane (sometimes referred to as liquid propane gas, or LPG), natural gas, and diesel.

Each of these fuel types can differ greatly in how they function, how long they last, how much they cost, and in how easy it is to gain access to them as well. Similarly, your choices will in turn vary depending on the type of fuel you are considering.

Jump to section:
Gasoline | Propane | Natural Gas | Diesel

Before You Purchase

Before purchasing, you’ll want to consider how, when and where you plan to use your generator and whether the type of fuel (or fuels) a particular model supports is best for these needs. You can always buy a generator that only runs on one type of fuel. Although typically lower in cost, with these models you significantly limit your options when the power goes out. An alternative to single-fuel portable electric generators are those falling under the category of “tri-fuel” generators. These types of generators will run on three types of fuel: gasoline, propane, and natural gas.

Portable Gasoline Generators

gas generator

The DuroMax XP4400E, a typical gas-powered portable generator, priced at around $400.

Gasoline-powered portable electric generators are the most common, due to the ease of access and relatively low cost of gasoline – it’s not necessarily the best option for all situations, but it’s what you’ll see most portable units using.

Because it’s the “standard” option, it makes sense to compare other fuels to gasoline when it comes to portable generators (rather than the other way around). With that said, here are some common concerns that come with gasoline-powered portable generators:

  • Gasoline has a very low flash point, and is an extremely flammable liquid. Many users forget that gasoline fumes are also flammable, and indeed catch fire more quickly than the actual liquid.
  • Most gas generators are also gravity fed, meaning that their fuel tank is at the top. It is important to let the generator cool down before refilling, as spilled fuel on top of a hot engine could spell disaster.
  • Stale fuel can cause engine and starting problems, so it’s best to empty old fuel between seasons if you don’t plan on running it for a while.
  • Although all engine types surveyed here require oil and filters, gasoline engines in particular require oil changes rather frequently – even as frequently as every 40-50 hours of operation time. To ensure that you do not break your engine, make sure to check the oil regularly and check it regularly according to the manufacturer’s instructions.

Conclusion: Compared to generators that run on other fuels, you will not find a wider range of options in terms of cost, power output, efficiency, quietness (operational volume), and portability than with gasoline-powered units.

Your car, lawn mower, and a bunch of other tools you own already probably run on gas. It’s familiar, cheap, simple to use, and (hopefully) you know how to store and handle it safely. Although not always the best option, gasoline generally works just fine as a generator fuel source. The other options are worth considering, though.

Portable Propane (Liquid Propane Gas, or LPG) Generators

champion 100263 dual fuel generator

Some portable generators, such as this 3400-Watt Dual Fuel model from Champion, can run on either regular gasoline or liquid propane (LP).

Propane is among the safest fuel options for portable generators, in addition to requiring little maintenance. Propane generators operate differently than those powered by gasoline and diesel. Since the fuel is already in gas form, they require no carburetor to mix a liquid fuel with air. Instead, they simply burn the gas to generate heat and electricity. With fewer moving parts, there is less that can go wrong with a propane generator – making them both extremely efficient and fairly easy to maintain.

Propane is easy to obtain, easy to store, and has a very long shelf life. Propane can be delivered to your home in large tanks, or you can purchase it from any number of hardware stores, supermarkets, gas stations, and convenience stores. Generators that run on propane are hooked up in much the same way as a gas grill or cast-iron burner for a turkey fryer/stock pot. This compatibility and ease of access provides you with a lot of flexibility and options when running on propane.

propane tank exchange

Propane tank exchanges (swap an empty 20 lb. size tank for a full one) are available at many gas stations, supermarkets, and hardware stores for about $20.

Benefits of Running on Propane

  • If you are running your generator on propane during a power outage and supplies are getting low, you can borrow the LP tank from your grill if need be.
  • The extremely long shelf life of propane means that you will not have to deal with emptying out the fuel after long periods. Simply disconnect the tank and store it safely until you need to use the generator again, or connect to your grill and use it for cooking.
  • Unlike gasoline and diesel (which require pumping), propane is usually obtainable during a power outage – providing a significant safety net for owners who were not prepared with fuel when a power outage strikes.

Drawbacks of Running on Propane

  • While you may enjoy a lot of flexibility with a propane generator, you will also find that it does not provide as much power and electricity in the long run.
  • Per gallon, propane costs are equivalent to gasoline, yet the fuel source burns through much faster because it is a gas.
  • Depending on your electrical load, a typical 20 lbs. gas cylinder can burn through in as quickly as 4 hours. That same cylinder may also last more than twice as long, again depending on your electrical load. Burn rate varies in this regard for all fuel types, but with propane it can be a little trickier to gauge how much you are burning and how much you have left.

Conclusion: Although propane is not the most efficient energy source for portable electric generators, many generators support dual-fuel or tri-fuel setups that typically include propane as one of the fuel sources, allowing for much more flexibility.

Portable Natural Gas Generators

generac 7043

There are relatiely few generators that are both portable and powered by Natural Gas. Most natural gas models, such as the Generac 7043, are permanently setup outside the house – running automatically when there’s an outage to provide power.

Using natural gas as a fuel source for portable electric generators has very clear positive and negatives.

Benefits of Running on Natural Gas

  • Natural gas is an extremely efficient fuel source, producing high amounts of heat with very little fuel.
  • Natural gas is extremely inexpensive when compared to all of the other fuel sources available for portable generators, making it a very attractive option.
  • Natural gas is extremely clean burning and does not require refilling. Much like propane, it is usually still available during power outages. (Unlike propane, you cannot purchase natural gas in tanks. Instead, it is feeds directly into your generator through fuel lines – which is can be an added benefit since you don’t need to leave your house to purchase more.)

Drawbacks of Running on Natural Gas

  • Although less costly to run on natural gas, there are often additional costs to get everything setup. Portable generators that can run on natural gas are not as “plug and play” as units running on gasoline; most portable units require a conversion kit or additional parts.
  • Also, there’s the matter of safe access to the gas itself. Safely tapping into your home’s gas line usually requires hiring a professional to setup a connection to the outside of your home.

Because portable electric generators almost never run solely on natural gas, maintenance for them is fully dependent on what other type of fuel source the generator takes. If you are using a tri-fuel portable generator that operates with gas, propane, and natural gas, your main concerns will be the same as with a gas generator.

However, if you are purchasing, or own, a dual-fuel system that runs on propane and natural gas, your maintenance concerns will mostly be related to regular check-ups. Ensuring that the system starts and is running, checking for cracks or fuel leaks, and scheduling professional maintenance at least once a year will help to ensure your machine is operating properly.

Conclusion: Tri-fuel generators provide flexibility, which is great – but, unlike the other two fuel sources, natural gas requires some infrastructure to be in place before it can be used. The expense of getting a gas line hooked up to work safely with your portable generator might still be worthwhile, but isn’t feasible for most people.

As an alternative, you should consider a permanently-installed home standby generator system that runs on natural gas (units start at around $2,000). They aren’t portable, but with these units you typically get a higher-capacity generator and a cleaner, safer integration with your home’s gas lines and power.

Portable Diesel Generators

diesel fuel sign

Diesel fuel can be found at most gas stations, particularly on major interstate routes.

Although large diesel-powered standby generators are a fixture at commercial/industrial facilities around the world, portable generators that run on diesel are not nearly as common as those run on gasoline. And, although it has some downsides, diesel is worth considering for several reasons.

Benefits of Running on Diesel

  • An important feature for diesel is its ease of access. Because tractor trailers and other large trucks run on diesel, it can be purchased at the pump right alongside gasoline. Many companies will even deliver diesel fuel, making it much easier to store in underground tanks that you may have installed on your property.
  • Because of its heaviness and density, diesel is the least flammable fuel source available for portable electric generators. As such, it is also the safest option to have.
  • Each gallon of diesel fuel will burn longer than that of gasoline, propane or natural gas. This means that a diesel generator will give more hours of operation than other generators. This makes a diesel-powered electric portable generator a better option for those that have limited fuel access.

Drawbacks of Running on Diesel

  • Although usually present at most locations, diesel is not available at all gas stations.
  • Diesel is generally more expensive than its sister product, gasoline. Despite its higher expense, you can expect to get a much longer life out of diesel (over the same amount over gasoline). This is due in no small part to its higher density.
  • Unfortunately, diesel engines tend to be fairly loud, making them much less preferable for average homeowners who reside in more suburban settings.
  • Higher price point (units start at around $1,500) and fewer choices (portable units are uncommon).
durostar ds7000q portable diesel generator

The DuroStar DS7000Q Portable Diesel Generator provides up to 5,500 watts of constant power (6,000 peak). Priced at around $1500, it costs about twice as much as a gasoline-powered generator with similar capacity.

Diesel engines are known for their durability and reliability, generally requiring less maintenance and input from the typical buyer than for gas-powered units. With that said, diesel engines do have their weaknesses. One of the worst things for a diesel engine is water – which causes corrosion on the engine parts, leading to failures.

It is also important to keep the portable generator’s battery charged. A diesel engine works under compression and heat, so it requires a battery that will heat up the compressed air to the correct temperature for ignition. The best form of maintenance for a diesel generator is using the correct type of fuel. Ensuring that you only use vehicle diesel fuel will help to stave off most problems that can arise with the generator.

Conclusion: If reliability is paramount, you already have equipment that runs on diesel, or have a specialized application in mind, diesel generators are worth considering. Otherwise, one of the other fuel types will be your best bet.