3 Best Diesel Generators – Fuel Efficient and Powerful

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Last updatedLast updated: February 21, 2021
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Generators are very useful when your regular power supply has been cut-off. It is a lifesaver in times of power outages and can help your business continue to have power despite electricity issues. Now, there are several types of generators on the market, with each one coming with different features and power using different sources. One of these are the diesel generators. In this post, we will review three of the best diesel generators that you can buy right now. These units come with the best features that you will require in any diesel generator.

When compiling this post, we considered some very important factors. Some of these factors include the type, starting system, peaked/rated watts, engine, fuel tank, runtime, outlets, noise level, warranty, dimensions, and weight. When all these factors are considered, then you will have the correct idea of a diesel generator to buy. With that in mind, let’s see the best options available right now.

Top 3 Diesel Generators Review 2021

1.

Generac XD5000EEditor’s Choice

Features
  • Type: portable
  • Starting system: recoil, electric
  • Peaked/rated watts: 5500/5000
  • Engine: 435cc, air-cooled, 4-cycle, Vertical Cylinder Diesel
  • Fuel tank: 12 gal
  • Runtime: 32.4 hours (50%)
  • Outlets: (2) 120-Volt 20-Amp GFCI Duplex Outlets NEMA 5-20R, (1) 120/240-Volt TwistLock Outlet NEMA L14-30R, (1) 120-Volt TwistLock Outlet NEMA L5-30R
  • Noise level: n/a
  • Warranty: 2-year limited
  • Dimensions: 33.1 x 22.5 x 25.6 inches
  • Weight: 254 lbs

Are you in the market for the undisputed best diesel generator on the market? Then look no further than the Generac XD5000E. This model comes from one of the best brands in the generator industry. Although diesel generators are not super popular due to their emissions and other factors, you can rest assured of excellent performance from this unit. The Generac XD5000E is from a line of portable options that will power most of your appliances with minimal fuss. 

Portable generators can be found in different models and have a wide range of power and performance. Where some offer just 1800W of power, others are even more powerful and can deliver up to 10000 Watts! The Generac XD5000E falls in the middle of this range of values. It comes as a 5000 Watt option. With this power, you can rest assured that it will help you to power most of the appliances, whether in the home, on the job site or your RV. Diesel generators offer plenty of power (as we will see in the buying guide later). 

At first glance, it is clear that the Generac XD5000E is a powerful option that will give you a lot of power and performance. It comes with a sturdy build that will remain right in place no matter how rigorous the process you put it through. It weighs 252 pounds, though, which is heavy and means that you will likely have it set up at a spot without frequently moving it. 

The weight might be alarming, especially if you are not used to diesel generators, but such heavyweight construction is popular with diesel generators. This build certainly comes with advantages. Because of the build, it works for a long time without any drop in performance. 

If you still want to move it around, the manufacturer has provided a wheel kit that will make it easier to move around. The Generac XD5000E is compatible with an electric start. However, this is not included in the package. You will have to get it yourself. 

One advantage of this generator and with most diesel generators is the lack of a carburetor. Since there isn’t a carburetor, you don’t have to stress yourself on maintenance. 

As indicated above, you can use this with an electric start, or you can use the recoil. For easier startup, we strongly recommend that you make the move to an electric start up. Using the generator is pretty easy and straightforward. For instance, it comes with a fuel primer bulb and a compression release lever. These two features come with their distinct advantages. The bulb makes it easier to restart if you used up the entire diesel in the generator. The lever, on the other hand, is handy in cold climates. 

As this model is a diesel generator, it runs longer than most other models on the market. It offers a lot of power – you get 5000 W running power and 5500 W starting power. With this much power, you have a generator to use for a wide plethora of appliance. 

The runtime is the best thing about the Generac XD5000E and is where it surpasses most of the rivals on the market. This powerful generator can run for 32 hours at 50% load! This is down to the efficient design and, of course, the 12 Gallon tank that it has. 

When choosing a generator, you certainly need to check out the connections that it has. Well, this generator doesn’t come with several outlets apart from the basic and most important ones. 

Although the Generac XD5000E is not a cheap option, it offers quite decent value for money. It runs all day and gives plenty of power. 

What we liked: With up to 32 hours of runtime, this is one of the best options in terms of runtime. It is built to last and will give you plenty of use over the years. Although it doesn’t offer all the fancy outlets found in other models, the outlets here are actually pretty useful and functional. 

What could be better: The only downside that we noted is the high price. It is one of the most expensive diesel generators on the market.

2.

Cummins Onan RV QD 10000Best for RV

Features
  • Type: standby
  • Starting system: remote
  • Peaked/rated watts: 1000/8000
  • Engine: 3 Inline Vertical 1647cc, 27HP
  • Fuel tank: 43 gal
  • Runtime: n/a
  • Outlets: n/a
  • Noise level: 68 dB
  • Warranty: 2-year limited & 5-year drive warranty
  • Dimensions: 41.4 x 24.5 x 27 inches
  • Weight: 765 lbs

There are several standby options on the market, especially when it comes to diesel generators. They offer different power ratings, and you have to consider the rating before making a buying choice. Well, the Cummins is an excellent standby unit that comes with excellent build and power. It has a peak rating of 10000 Watts. However, the kicker is in the running power. The Cummins has running power of 8000 Watts. This is far higher than what is found in the Generac model that is our top pick. Because of rating, there is almost no place that the Cummins can’t be used, which makes it the best diesel generator for RV. It is super powerful and will help you with all of your appliances.

Before we highlight all the advantages of the model, let’s get the downside out of the way. The main problem is the portability. It isn’t portable in any sense of the word. As a standby option, it is designed to be set up on a spot and work from there. It weighs more than 750 pounds, so there’s no chance of having your friend transport it for a camping trip or something like that. Aside from the zero portability, though, everything else is excellent in the Cummins Onan RV QD 10000. 

The Cummins is specially made for RV use and can handle plenty of appliances simultaneously. With the model, you can even run up to three AC models at a time. Due to the plenty of power that we have indicated earlier, this RV generator is also useful as a home standby option. 

The design is decent, and it certainly looks the part of a super-diesel generator. The design is made in such a way that the fuel tank lies outside the body. Therefore, you must have a connection between the tank and the engine. In terms of fuel efficiency, well, the Cummins offers cool performance. It lets you use a relatively small amount to diesel on a load. 

All the features we have discussed above are cool, but the best thing for use is that you can remotely control plenty of the features. Additionally, there is a microprocessor and wave output that will run diagnostics on the generator and see if there are any problems with it. With this feature, you can tackle problems before they become anything serious. This will help to drastically reduce the cost and frequency of maintenance. 

Although the Cummins is a powerful model, it should be noted that it is one of the quietest options in its category. To that end, Cummins have included useful features like a muffler, noise-reducing casing and more. When all the features are combined, you have a relatively quiet model.

Another notable feature of this generator is the type of start. There are two ways to start the generator. The first method is via electrical start. The other is via remote start. Therefore, you can start the generator without being near it. 

What we liked: Overall, this is a big source of power for your RV or an emergency standby generator. It offers a design that is great, especially if you are running sensitive appliances in the RV or home. 

What could be better: This unit is completely non-portable. There are no wheels or any kit to help you to move the over 750-pound generator. 

3.

Generac RD03022ADAEBest Standby Unit

Features
  • Type: standby
  • Starting system: automatic, manual
  • Peaked/rated watts: 30000
  • Engine: 2200cc Perkins, 1800RPM
  • Fuel tank: 61 gal
  • Runtime: 41.6 hours (50%)
  • Outlets: n/a
  • Noise level: 65-70 dB
  • Warranty: 5-year limited
  • Dimensions: 95 x 35 x 59 inches
  • Weight: 1857 lbs

Although it is a standby option like the Cummins, and a Generac model, the Generac RD03022ADAE is quite different from either units. Let’s see the features of this model.

As a standby model, this model offers plenty of power. Where the Cummins above gave a 8000W power rating, it is absolutely overshadowed by the power of the Generac RD03022ADAE. This model offers a 30000W rating! Therefore, you can use it to power so many appliances at a time. It is a powerful option and will meet your power requirements with minimal fuss. 

The engine is powerful and will work for a pretty long time without needing your maintenance or stuff like that for a very long time. 

As with most standby generators, the portability is the only issue with the Generac RD03022ADAE. If you thought the 750-pound weight of the Cummins was much, then you’ll certainly be stumped by the 1857 pound weight of the Generac. Therefore, it is not designed to be wheeled around or transported without using some vehicle. 

  Where the Cummins is great for RV use, this model is certainly not designed for that purpose. 

The enormous power this unit gives ensures that you can run several appliances simultaneously. It is excellent for commercial use and would likely be overkill for home use. 

The design isn’t anything special, but it is made of high quality materials which mean that it will last for a very long time. There is a 41-hour runtime that means you have just the generator to run for a long time. Additionally, the 61 gallon tank means a large capacity to use for a long time. It is quite economical as well. You can use little diesel for an extended time. 

Unlike the Cummins, though, this model does not feature remote start. Instead of that, it offers automatic and manual start. Either way, it is relatively easy to get the model up and running. 

Although the Generac RD03022ADAE. is a powerful model, it should be noted that it is one of the quietest options in its category. To that end, Generac have included useful features like a muffler, noise-reducing casing and more. When all the features are combined, you have a relatively quiet model. It only produces about 70 dBs of noise. 

What we liked: The Generac RD03022ADAE is a powerful standby generator with good fuel economy, durable build and overall excellent performance. 

What could be better: This is an excellent model, but it is super expensive. 

Things to Consider

In the section above, we considered three of the best diesel generators on the market right now. All of them come with different features, and by providing the list, we have helped you to narrow down your choices. In the buying guide section, you will see all you have to know about these generators.

How These Generators Work

You’ll likely be interested in how these work, since that gives an idea of the differences between it and the other types of generators. The working mechanisms of a diesel generator are varied from a generator that is powered by gasoline. So how does it work?

Well, with the diesel engine, your air and fuel are introduced at the same time. This combination in the engine combusts at a higher temperature than what is obtained in a gasoline engine.

It is this higher temperature that makes diesel generators more efficient than their counterparts on the market. The compression ratio is higher here than in your gas engine.

Whether you have a diesel engine or a gas-powered engine, they are both referred to as internal combustion engines – reasons for which are quite clear.

To ignite and give power, the gas engine needs to spark ignition, but on the other hand, the diesel engine is reliant on the compression of air that triggers the ignition.

Advantages

3 Best Diesel Generators - Fuel Efficient and PowerfulWith this knowledge, which is better? Well, let’s see some of the advantages of the diesel engine.

  • More efficient

The first advantage of the diesel powered generator is that it gives better fuel efficiency. This has been mentioned earlier. Because a higher temperature is required for combustion, the diesel generator uses less fuel over time. This benefit is linked to other advantages.

  • Run Time

The fuel efficiency certainly helps with the run time of the generator. You can use it for a longer time at a go. Additionally, these generators also come with better quality construction. That way, it can work for a longer time without any damage to the engine or other parts of the generator.

Due to the design, some of these generators can have a fuel tank attached to them. An example is the Cummins Onan RV QD 10000. Because of this, it will run longer than gas-powered models.

  • Design

From our research and reviews from other users, it has been observed that diesel engines offer sturdier engine construction. In addition, all the parts attached to the engine are designed to withstand heavy vibration and use. Thus, you can certainly use it for a long time.

  • Economical

Since the diesel generator offers you lower fuel use and better efficiency, you will spend lower on fuel.

  • Safety

Another notable advantage of the diesel generator is the better safety. Right from the fuel used; it is clear that diesel generators are safer. Diesel is not as flammable as propane. Therefore, you will have a lower risk of a fire accident occurring. Another reason why people prefer this engine is that there is no spark for ignition. Therefore, the chances of unintentional combustion is far lower.

  • Maintenance

Since a diesel generator does not use plenty of moving parts and features overall simpler mechanics, it is easier to maintain it. It also doesn’t break down as often.

Disadvantages

3 Best Diesel Generators - Fuel Efficient and PowerfulTrue, there are many reasons why it makes sense to have a diesel generator, but to make a balanced decision, it is important to consider some of the cons of getting this type of generator.

  • Expensive

When compared to other types of generators, from petrol powered to gas-powered, a diesel generator is quite expensive. The advantage it has, though, is that it is more durable. However, when compared to generators that give the same amount of power, the diesel generator is certainly costlier.

  • Low Diversity

There are simply hundreds of models of generators powered by petrol or gas. However, the diesel powered generator has only a few options. Therefore, it can be quite the challenge finding the model that would meet all your requirements.

  • Portability

One disadvantage of these generators is the portability. These generators are heavier than the regular options and quite heavy. Most of the models that we reviewed above weigh 500 pounds.

  • Not great in the cold

Since this is a combustion engine, you might find it difficult to start the generator in the cold weather. The cold temperature will make it more difficult for the engine to get the maximum temperature needed for combustion. Some models, however, have contingencies in place for such an occurrence.

  • Noise

If you want a quiet generator, then you might have to look elsewhere in this regard. Diesel generators are simply so loud in operation.

With all these advantages and disadvantages, which option should you choose? Well, there is no hard and fast rule on which of the generator types are the best.

However, if you are looking for a generator for long, heavy use, the durability and run time of the diesel generator might swing in its favor. However, if you want a portable, quiet, affordable generator, then you might want to consider the other types of generators.

Features to consider

3 Best Diesel Generators - Fuel Efficient and PowerfulIn this section, we will consider the important features that will affect your buying choice.

Type

There are different types of diesel powered generators, and the type is something that will determine which is best for you. These generators come from several companies and have some unique features.

  • Industrial 

As the name implies, this type of generator is designed for industrial use. It is usually a standby model as well and comes with all the features needed to help carry the load of industrial applications.

If you have a high power demand, then the power generated by this type of generator can help you out. Additionally, they have a long run time. An example of this generator is the Generac RD03022ADAE. 

  • Residential Generator

The residential models are also self-descriptive. They are not as large as the industrial models and are used in homes, small shops and similar places that do not require an enormous amount of power. They are excellent and will help to carry the load of sensitive appliances. An example is the Generac XD5000E.

Cooling system

As the generator works, it produces, among other things, a great deal of heat. If the heat is not managed, it can result in overheating and can damage the generator. Manufacturers have sought to solve this problem; therefore, there are some things put in place for such purpose.

  • Air-Cooled Generators

This type of system, as the name implies, is cooled by air. It often has an air-intake system that drives cool air through the generator.

  • Water-cooled generator

In this type of generator, cool water is used to reduce the heat of the generator. Most of the units with this type of technology have different setups for cooling.

Both systems are effective in cooling the system. However, the water cooled models need to be maintained more frequently than the regular options.

Power

This is arguably the most important feature to consider. After all, the aim of a generator is to power your devices. If the generator isn’t powerful enough, it will simply be unable to carry the load. Thus, ensure that you consider the power output of the generator and compare that with what you plan on carrying with it.

Diesel generators come with different power outputs. The Generac RD03022ADAE. For instance has up to 30000 Watts running power output. Therefore, it will easily take care of the appliances. You can therefore use it in commercial setups without any bother.

Some are less powerful; for example, the Generac XD5000E has a much lower power output. Thus, it is more suitable for portable, home use.

As said, look at the rating on the generator and compare that with the load that you are looking to carry.

Phase

One area of diversity in diesel generators is in the matter of phases. These generators can come in either single phase or three phase connections. Therefore, before you make your purchase, check out the phase of your intended location and choose a compatible generator.

Fuel Consumption

For most options, the more power the generator generates, the more fuel it would consume. Aside from the initial price of the unit, it is important for the potential buyer to consider the fuel consumption of the generator.

To find out just how much it might consume, consider the reviews from users. You should endeavour to see the efficiency of the unit as well depending on the load that it carries.

Ease of Use and Management

Some diesel generators are designed to be as convenient to use as possible. That is why they have automatic power transfer during a power outage or when the power comes back on.

The control panel should also show the important information like fuel level, and other important data that will boost the overall efficiency of your unit. All these features might seem small, but they add up to give a more convenient, fuel-saving generator.

Dimensions and Portability

Generally, diesel generators have large sizes and are usually heavy. That is why the portable options usually come with wheels or can be attached to a wheel kit. The Generac XD5000E, for example, has a wheel kit for easier transportation. If you will be moving the generator around often, then we recommend that you choose such a model.

For industrial settings, though, you might prefer a standby option. These are usually very heavy, with the Generac RD03022ADAE, for example, weighing more than 1000 pounds.

Noise

Generators are noisy by nature, although some are louder than others. If you want some level of quiet, then look for diesel generators that are relatively quiet.

Warranty

As with other appliances on the market, issues can arise with the performance down the line. Therefore, it is recommended that you look for an option with a lengthy warranty. That way, you can replace or replace the model in case of damage.

FAQ

The answer depends on the model of the generator. Some models are designed to be used in all weather – especially standby models.

Yes. The safety tips are the same with every other generator. Ensure that the connections are dry. The voltage supplies should also be switched off before you turn on the generator.

These generators are very fuel efficient. They use less fuel than most of the other types of generators.

There are two steps to take.

First, calculate the starting wattage of the appliances that you want to run.

Compare this value with the generator and ensure that the generator has enough power that exceeds the wattage of all the appliances.

Conclusion

Diesel generators are arguably the least popular types of generators on the market. However, they offer plenty of advantages as they are very fuel efficient. We recommend the three models on this roundup.

The best model is the Generac XD5000E. This unit offers excellent build quality, a good feature set, decent value for money, and exceptional runtime performance. All these make it one of the best diesel generators on the market today. If you have an RV, then the Cummins Onan RV QD 10000 is the best option. This model is the best for your RV. It is powerful, built to last, has an impressive Sine Wave Output, and features remote start. If you are looking for power, the Generac RD03022ADAE is one of the top choices. This unit is a very powerful option that is designed mainly for standby use. It is efficient, easy to start and will power every single appliance that you have.

Use this review and guide to know how to choose the best diesel generators today.

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