Propane vs diesel generator: Which one is best for you

Propane is an affordable, reliable, and instantly available fuel that can provide your family with safety and comfort in the event of a natural disaster. Do not leave your family’s safety and comfort to anything …

propane vs diesel generator

Propane is an affordable, reliable, and instantly available fuel that can provide your family with safety and comfort in the event of a natural disaster. Do not leave your family’s safety and comfort to anything but propane.

Diesel generators are more expensive than propane generators, but they have many advantages over propane generators including:

  • The ability to run for longer periods of time without refueling
  • A greater capacity to produce power
  • More efficient operation
  • Easier maintenance
  • No emissions

If you want to be prepared for any emergency situation, consider purchasing a propane generator. It will save you money on gas costs, it will give you peace of mind knowing that you have a backup source of energy in case of emergencies, and it will help keep your family safe during times of crisis.

Also Read: Can you run a propane generator on natural gas? Complete Guide

What are some of the benefits of propane generators?

propane is readily available

As opposed to diesel and gasoline, which require electrical pumps to reach customers, propane is readily available in times of emergency, such as ice storms, hurricanes capable of severing the electrical grid from your home, or other natural disasters causing power outages. It is possible to purchase standard-sized tanks in every community in case of a sudden power outage. Propane is a clean-burning, efficient, and safe fuel that can be stored on-site for year-round use. It can also be delivered right to your home or business, avoiding long lines at the pump.

propane generators start easily

In contrast to gasoline, which often develops “gum” deposits, or diesel engines, which are notorious for difficulty starting in colder temperatures, propane generators are easy to start. In just a few seconds, a propane standby generator will start providing power when there’s a power outage. Since propane does not need fuel additives or degrade over time, it is always ready for use.

propane generators provide longevity over diesel generators

Additionally, propane engine generators are not susceptible to the problem of “wet-stacking” of fuel injectors that plague diesel systems without a direct load. Over fueling can cause sputtering, rough running, and excessive smoking in diesel engines caused by carbon deposits.

Besides being reliable and easy to use, propane generators last for thousands of hours, and require less regular maintenance, making them ready to use whenever needed.

Propane vs diesel generator

Weight and Size

In fact, diesel generators come with embedded fuel tanks, which make them a better choice if space is an issue.

Alternatively, propane generators are not equipped with embedded tanks (as this would be quite dangerous). You will need to connect an external propane tank to this type of generator, so on top of the generator and the cables supplying your devices, you will also need a propane tank cable.

You do not want this, especially if the area where the generator is located can, by accident, be accessed by uninvited people (if you work in a field) or very small children.

My question, however, is whether the weight and size of this generator are affected by its design.

What is the difference between propane and diesel generators in terms of weight? The weight of the generator is not affected by the fuel type, especially for portable generators. For example, a 7000W rated power generator (excluding fuel tank) will still weigh approximately 200 pounds regardless of whether it is propane or diesel powered.

Nowadays, you may also notice that “dual fuel” generators are becoming more and more common (such as the Pulsar on Amazon, for example). These generators can run on both propane and gasoline. This is another direct indication that the engine is not that different for both fuels.

Moreover, a few hardcore Youtubers also attempted to convert a diesel (or gasoline) engine to propane (or natural gas). Although it is possible to do so, I would not recommend it (considering how expensive generators are nowadays if you break yours) since it is not easy.

It was not found that portable generators’ size was affected by fuel type. I did not notice a significant difference in a diesel or propane generator’s size (again, excluding the propane tank). They both occupy a volume of around 23 inches for an average 5000W rated power, for example.

For those of you camping, I would avoid propane generators. The tanks will add a considerable load. I would recommend a small size diesel generator instead.

Also Read: Top 6 Best quiet generators for food trucks

Fuel Price

As discussed by the USA EIA, the USA produces around 1.8 billion barrels of diesel compared to 1.5 billion barrels consumed. Moreover, the USA is exporting more propane as a result of its growth in home production. Therefore, both fuels are readily available in the country.

The price, however, is another matter.

How stable is propane price compared to diesel? The price of propane and diesel fluctuates very similarly. According to this interesting comparison, diesel and propane are produced using similar processes, so they experience similar price fluctuations. As illustrated by the EIA study, diesel prices have been continuously rising for the last 15 years from 1 to 3 dollars per gallon (for residential use).

Propane is not more expensive than diesel. Its price changes throughout the year and is comparable to diesel. However, this does not mean propane generators are more expensive to run than diesel generators.

Diesel is around $2.3 per gallon, while propane is around $2 to $2.8 per gallon (assuming domestic use). Hence, propane is around one third the price of diesel per volume.

What is the cost of running propane generators compared to diesel generators?

According to a fair assessment which considers both the retail price and fuel energy density, propane generators are more expensive to operate than diesel generators.

The cost of operating a generator depends mainly on the amount of electricity that can be produced from that given volume of fuel, not only on the price of fuel per unit of volume.

A gallon of fuel (let’s call it to fuel A) costs half as much as another fuel (let’s call it fuel B) so it is not necessarily cheaper to run a generator that uses fuel A. For example, if fuel A (the half-price) produces just one tenth as much energy as fuel B, then the energy produced by fuel A will be much more expensive, even if the fuel is cheaper per volume.

A gallon of diesel can ideally produce at most 33 kWh of energy. However, one gallon of propane can only produce 27 kWh of energy. Thus, doing the math, one gallon of propane will produce 8.8 pennies of energy per kWh (amount obtained by dividing $2.4 by 27kWh), whereas diesel will cost 7.3 pennies per kWh (amount obtained by dividing $2.4 by 33kWh).

Obviously, you need to be cautious. Each kWh of electricity that you generate with your generator is going to cost a lot more than the 7c I calculated here for both fuel types. That’s because I skipped the efficiency of the generator to make the technical analysis easier.

Only 20% of the 33kWh of energy in one gallon of diesel can be extracted by the generator. It sounds little, but 80% of your fuel’s energy is lost.

We can estimate that diesel generators are 22% cheaper to run than propane generators (44c per kWh for propane, 36c for diesel).

Fuel Availability

It is important to keep this in mind when choosing a generator. You do not want to get bogged down in technical details, only to find that you cannot use the generator when you need it.

It is important never to confuse propane with natural gas. They are quite different types of fuel. Propane, unlike natural gas, is not distributed through pipes.

The gas companies may deliver compressed liquid propane (LCP) to your doorstep in many countries, including the US and the UK so that it can be connected to your generator immediately. In addition, some petrol stations can refill your empty propane tank when you are queuing to fuel your car. When you are queuing up, just ask. Once the tank is empty, they can come back to collect it next time when they bring a new one.

The same cannot be said with diesel. I am not aware of any company that delivers diesel at home. So, in such a case, you have to get out of the house and go to the nearest diesel station. In comparison to waiting for propane delivery or finding a propane station (in working hours), you can have diesel on-demand without delays and all the time (gas stations are open 24/7).

Since diesel generators can be funded almost everywhere, at any time, they are a better option if fuel availability is a concern.

In RVs, propane is not an issue because many of your devices (such as refrigerators) already run on propane, and its lack of availability (or extra effort to get it) is not a problem.

Fuel Storage – Shelf Life

In properly sealed tanks, propane fuel lasts far longer than diesel fuel. Propane generators can be used to run in moments of emergency, without delay, if you have a safety backup of fuel in your garage.

Let’s look at the three main categories of portable generator users to understand why:

  1. Those who live off-grid for their own reasons, such as traveling with their RV;
  2. Those who need to work on-site;
  3. In case of an emergency, those who require their main home appliances;

If you belong to the third category, you will probably be interested in how long you can store your fuel so that it can be used when needed. In case of extreme weather conditions, you don’t want to get out of your house to the petrol station (that might even be unavailable, flooded, or plenty of other people just doing the same).

It is possible for a simple tank of diesel to last as long as a year without any special maintenance, or it can last as little as 6 months in a warm environment.

The most common problems are moisture and fungi growth (yes, living forms can grow on diesel). Old diesel can be easily identified by its odor and fungus growth.

Can you tell me how long a propane tank lasts?

Pressurized propane tanks can last for 20-30 years. This is around 20 times longer than diesel tanks. Propane tanks have a shorter shelf life than the fuel itself.

As a result, I recommend propane generators if you want to use them primarily for emergencies. A propane tank will surely serve you well years from now.

Also Read: Do apartment complexes have backup generators?


It is not the type of fuel that determines how loud a generator is. Propane generators are just as loud as diesel generators.

There is, however, a catch.

Many claim that portable diesel generators are quieter. Those people are not lying. Their diesel generators are quieter simply because they are very likely inverter generators. These are a special type of diesel (and even propane) generator. In case of variable loads, their speed will be optimized (not maximum) thanks to an extra special device (the inverter).

As a result, what makes them quiet is the inverter, not the fuel. Propane inverter generators (a bit less common than diesel ones in my experience) are just as quiet as diesel inverter generators.

It is also possible to demonstrate this aspect using conversion kits. A conversion kit consists of a bunch of cables and plugs that need to be connected to a generator in order to change its fuel. You can easily convert the Honda 2200i from (gasoline, not diesel, but the concept is the same) to propane. The only thing that changes is the fuel that explodes within the cylinder.

However, the engine does not change at all, the explosion of gas (that causes the noise in the first place) happens in the same way, and the cylinder (that contributes to the noise) moves as before. Here’s a video that shows a before and after fuel conversion (it’s for gasoline, but the concept applies to diesel as well).

Consider an inverter generator if noise is a major concern. You can choose from propane, gasoline, or diesel. Your decision will be dependent on the other factors discussed here.

There are, of course, exceptions to all of the above when it comes to large backup generators. This discussion is focused on portable generators (those you can carry around). Depending on the size of the backup unit installed permanently in your garden, it might have a more complex (and expensive) engine that makes a difference in noise.

According to a few friends who install backup diesel generators, they are noisier than their propane counterparts.


If you cannot place a generator far enough to avoid exhaust fumes reaching your house, propane generators emit far less carbon dioxide and NO2 gases than diesel generators.

Nevertheless, as an engineer, I am curious to know how environmentally friendly propane generators are. Are they half as polluting as diesel generators?

Compared to diesel, propane emits 161 pounds (73kg) of CO2 for 1 million Btu, 139 pounds (around 63kg) for 1 million Btu. Without getting too technical, a Btu (British thermal unit) is the amount of energy that is produced by a fuel. This means that diesel produces 14% more CO2 than propane given the same energy (and therefore electricity). While reducing our carbon footprint is important, it is not as significant as some have claimed.

Despite producing less CO2, fuel also produces other (even in smaller amounts) more dangerous chemicals, such as Nitrogen Oxide. If you have a basic understanding of chemistry, you will see these gases under the name NOx or N2Ox family. By reacting with our air, these gases cause ozone (O3) and acid rain [PDF].

Due to different types of engines, manufacturers, and the fact that such information is often omitted by the label “CARB compliant”, it is quite difficult to find reliable quantitative information about the variation of NO2 emissions when switching from diesel to propane.

This study [PDF] shows how by replacing diesel with propane with engines the emissions drop from 160 ppm to 40 ppm. As a result, I would not take this as absolute truth (as the engine was probably from a car) but rather as an indication.

Propane, on average, emits less NOx than diesel, so we can call it a cleaner fuel.

Aside from the above, diesel also produces ash. According to the University of Wisconsin [PDF], this phenomenon affects all filters of diesel-powered engines. Propane, however, does not produce nearly any ash once burned, according to the University of Wisconsin [PDF].

Carbon monoxide (CO) is produced by both, as it is an odorless bioproduct that can poison you without you realizing it. Despite propane producing less CO per gallon (compared to gasoline), it does produce enough to be hazardous. Because of this, portable generators should never (ever) be used in close proximity to windows or doors, regardless of the fuel they use.

propane vs diesel generator

Safety Handling

A propane or diesel explosion is the main risk from handling such fuels if they are spilled or released out of the can (tank) containing them. Due to the high damage that can result from propane spills, primarily because of its gas nature, such fuels are more dangerous to handle.

In the environment, diesel is a danger because it can be easily spilled by accident. It is just a liquid stored in (hopefully) a sturdy plastic can. However, even if some droplets end up on your generator, or even on your clothes, this is not a big deal. If you get any droplets on your clothes, wash them separately from others and clean them with a towel. Diesel doesn’t ignite as quickly as gasoline or propane, so be careful.

The gas that diesel can release when it evaporates can be a serious hazard if you drop it on the floor, or somewhere else. Avoid what the guys below did (or did not do). Anything hot or able to produce sparks should not pass near you at all costs.

Unlike diesel, propane does not spill out of the tank so easily. It is designed to prevent spillage, which can be extremely dangerous. However, if this does occur, it is much more likely to cause serious damage than in the case of diesel.

Gases cannot be seen in the air, while diesel can be clearly seen on a surface. However, commercial propane can be smelled, since natural propane is odorless by nature.

In addition, gas is a poor friend in general. It tends to take up a lot of space. One of the most common accidents occurs when transporting a propane tank in your car. If you lay the propane tank horizontally, the security valve can become slightly loose by accident.

If this happens, your car might fill up with gas. This is the worst place for this to happen because sparks and high engine temperatures are a recipe for disaster. Open all the doors, leave the car, and call the fire department right away. To avoid problems, keep the propane tank outside and upright (hard plastic support can be used to assist in this).

If the propane line transporting the gas to the generator is broken (or if the valve is not in perfect condition), serious damage can result.


The stability of propane fuel (which degrades dozens of times slower than diesel) and its cleanliness make propane generators easier to maintain over time. The dirtier the fuel, the more particulates it creates. By accumulating within the engine (cylinder, exhaust stack), these particulates cause a blockage, causing a decrease in efficiency first and malfunctioning if left untreated.

Unlike propane generators, diesel generators require more attention and maintenance over time. Among the most common problems with diesel generators, but not propane generators, are wet stacking, corrosion, clogged filters, and increased fuel consumption.

Wet Stacking

Stacking occurs when diesel generators run too often at a low load, causing the fuel to not burn properly, resulting in a higher percentage of carbon accumulating inside the cylinder.

The dry carbon particles absorb moisture from the surrounding air exhaust gases, leading to the creation of a black and oily liquid in the exhaust stack (here referred to as the “wet stack”).

Also Read: Should I Use Generators Indoor Or Outdoor?

Clogged Filters

Diesel left in the generator tank for more than a month may cause fungus growth, engine cloaking, and water separation.

Once you have finished using a diesel generator (because the tank is embedded) it is tempting to leave the fuel in the tank. This is not recommended.

As a result, diesel tends to develop sludge, an algae-like substance that forms clumps and adheres to the tank walls and the water, eventually clogging filters.

For this reason, diesel should always be removed from the tank of a diesel generator. If the generator will be used within a month or less, the fuel can be left in the tank, but diesel stabilizers should be used.

The gas from a propane generator must also be taken out for security reasons (by letting the generator run without a gas connection so that it exhausts the gas remaining in the engine). This is not a matter of causing damage to the engine, but to ensure future safety.


A diesel generator’s rubber components can become corroded if not removed. The carburetor (the small component that mixes air and fuel) contains rubber and brass elements that can be consumed by diesel over time. Before leaving a diesel generator aside for a long time, you need to clean the carburetor (follow manufacturer’s instructions).

Please note that I am not stating that portable propane generators do not need any intervention. Portable propane generators share many of the same parts as diesel generators. Consequently, many of the problems that affect diesel do also affect propane and they do require regular maintenance (such as air filters, oil replacement, etc…)

Due to the fast degradation of propane, the frequency of such interventions is less when compared to that of a diesel generator, even with the same amount of working hours.


A diesel generator has difficulty starting at temperatures below 30F (-1C). This is called the “cold start” problem. In cold environments, propane (or gas-based generators) is a better option than diesel generators.

Firstly, diesel engine fuel temperature heavily affects the evaporation process. As the temperature decreases, vaporization (the process in which your diesel needs to turn into vapor/small droplets) becomes increasingly difficult. As propane is a gas once it leaves the tank, this is not a problem.

The second factor that explains the cold start problem is the higher (than propane) temperature required for diesel to start the combustion. The entire engine gets cold in cold weather. The cylinder, piston, and frame are all cold. Therefore, the diesel engine of your portable generator will have a more difficult time reaching the necessary temperature (thousands of kelvin) through compression.

At first, the energy generated by compression is lost in the cylinders and pistons rather than in the fuel-air mixture.

It is important to note that the above problem may not apply to every diesel engine. Certainly, car diesel engines, especially modern ones, do not have the same problems (at least not as badly as in the past). However, a small portable generator for just a few hundred dollars does not have the same quality as a car engine. As a result, do not expect the same performance.

You can also purchase starting fluids and apply them to your generator’s carburetor if you are able to warm up the generator (place it in a warmer environment, never run it indoors).


Thus, if you have read all the discussions on propane generators vs diesel generators, you should have a better understanding of what is best for you (or at least a better understanding).

Propane generators are cleaner than diesel generators;

Diesel generators and portable propane generators have very similar noise levels. Inverters are what make portable diesel generators quieter than open-frame (no inverter) propane generators.

If you want to store propane, you will need more space because it has less energy density than diesel;

It is possible to store propane for a decade or more in a cool environment. However, diesel starts degrading as soon as a few months pass;

The high degradation rate of diesel fuel might require more maintenance on diesel generators than on propane generators;

A propane generator may be more suitable for RVs since propane is already used for other appliances inside the RV. Furthermore, RV generators will be placed closer to the residents.

Also Read: Top 6 best portable gas generator for home use


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