Top 3 Diesel Generators – Reviews and Buying Guide

39 Models Considered
51 Hours of Research
3 Experts Interviewed
230 Reviews Analyzed

Generators are powerful machines with the capacity of giving and distributing power to all electrical appliances you need at once, depending on the power rating and the number of electrical appliances in your home. There are various fuel options to choose from to power these generators like diesel, natural gas, and liquid propane. Diesel generators offer the same power, but they outrun other generator models in terms of ease of maintenance and durability.

Diesel generators are quite rare, but the features to take into account are the same as with other generator types. They include the engine and fuel consumption which checks for the cost-effectiveness and how much fuel is consumed per time. Another important factor to take note of is the power output of a diesel generator; the power output determines the number of electrical appliances a machine can power depending on the rating of such a machine. The last but not the least feature to be aware of is the tank volume which determines the amount of fuel the diesel engine can take in at a go. The higher the tank volume, the longer it takes for the fuel to be exhausted.

Top 3 Diesel Generators Review 2018

We spent three dozens of hours researching into diesel generators to come up with three best models available online. Below is a table with a round-up of three best products, followed by more in-detail reviews of each model, complete with pros and cons. We also summarized everything you need to know about diesel generators in the buying guide below.

Name and Features Image Rating Price
1. DuroStar DS7000Q (Editor’s choice)
Powerful generator that comes as a great price for the features, runs for 12 hours at half load, is highly efficient, and boasts a soundproof muffler system feature for quiet operation
DuroStar DS7000Q image
2. Generac 6864 (Most Durable)
Durable generator with an industrial-grade engine that comes with a large 12-gallon fuel tank and an impressive runtime of 32.4 hours at a half load
Generac 6864 image
3. SIGMA 7000W (Budget Pick)
Reliable generator with a high peak power of 7000W and a rated one of 5,500W, which is enough for most appliances and electronics
SIGMA 7000W image
Features
  • Engine: 4-stroke single-cylinder direct injection diesel engine, 3600 RPM
  • Peak Power: 6,000 W
  • Rated power: 5,500 W
  • Dimensions: 37.8 x 22 x 30.3 inches
  • Weight: 305 pounds
  • Tank volume: 3.83 gal.
  • Runtime: 12-hour run time at 1/2 load
  • Warranty: 1-year limited

More features:  remote start and/or electric start, oil alert automatic shutdown, volt meter, circuit breakers, low fuel indicator

OVERALL RATING: 9.7 out of 10

DuroStar DS7000Q is a diesel generator that is ideal for almost every situation you find yourself from emergency power outages in your homes to the high demand of power supply in farms, maintenance and construction sites and so on.

The diesel generator operates with a four-cycle air cooled, single cylinder diesel engine that makes use of a very advanced system for fuel injection that reduces the rate at which fuel is being consumed. It boasts of peak power of 6,000W and a constant of 5,500W. It comes in a fully enclosed frame and has a soundproof feature as well as a super quiet muffler. These features help the DuroStar DS7000Q diesel generator in noise reduction and smooth operation.

The electrical part of the generator is packed with a durable and reliable alternator with an automatic voltage regulator to step down or step up an anomaly in power generated. The power panel features the main controls, including a start switch, volt meter, and circuit breaker. It offers two 120-volt, 20-amp, 3-prong outlets (with ground fault interrupter) to supply power to all your home appliances, plus two twist-lock outlets for high-powered tools: one 120-volt, 30-amp, 3-prong outlet, and one 120/240-volt, 30-amp, 4-prong outlet.

The generator is backed by a 1-year limited warranty.

PROS:
  • Super quiet and smooth operation due to its soundproof muffler system feature
  • Efficient
  • 12-hour runtime at half load
  • High peak and rated power
  • Easy to run
  • One year backed warranty

CONS:
  • Does not have a pre-installed hour meter clock
  • Smaller Fuel tank volume compared to the GENERAC 6864
  • Takes much space
  • Smaller runtime at half load compared to the GENERAC 6864

Features
  • Engine: Yanmar LW Series 435cc air-cooled direct injection, industrial-grade diesel engine, 3600 RPM
  • Peak Power: 5,500 W
  • Rated power: 5,000 W
  • Dimensions: 33.1 x 22.5 x 25.6 inches
  • Weight: 254 pounds
  • Tank volume: 12 gal.
  • Runtime: 32.4-hour run time at 1/2 load
  • Warranty: 2-year limited

More features: durable, fully welded 1 1/4″ steel frame

OVERALL RATING: 9.0 out of 10

Probably the best thing about this diesel generator is that it is more efficient and provides consumers with a long-life span. It comes with the Yanmar LW Series 435cc air-cooled direct injection, EPA Tier IV, industrial grade engine. It has less than 6% total harmonic distortion for the clean and smooth operation of sensitive electronics, tools, and applications.

The generator boasts a 12-gallon fuel tank with a fuel gauge that provides a long runtime of 32.4 hours at 1/2 load. The compression release lever provides easier starting during cold ambient temperatures. It also comes with a feature called the “low oil pressure shutdown” that enables the system to shut down when it is low on oil pressure that automatically safeguards the engine from damage.

The generator also comes with a fuel primer bulb that provides quicker starts when the fuel tank has previously run empty. The generator itself is highly durable and welded with steel frame. It has an Integrated Lifting Eye which provides easy transport and security in the location where it is placed.

A great advantage of this generator is that its 120/240V selector switch provides full 120V power, or you can switch it to 240 V if you need. The single touch electric start provides hassle-free start up whereas the battery is not included. Finally, it has the hour meter feature along with maintenance resets tracks usage and monitors maintenance cycles. It also comes with an additional corded electric power source.

PROS:
  • Generates much power
  • Durable and reliable
  • Large fuel tank volume
  • Long lifespan
  • Portable

CONS:
  • Does not come with a pre-installed battery
  • Pricey
  • After battery installation, there are issues with the pull start
  • Loud

Features
  • Engine: direct injection, vertical, four cycles, air-cooled diesel, 3600 RPM
  • Peak power: 7,000W
  • Rated power: 5,500W
  • Dimensions: 37.5 x 22.5 x 30 inches
  • Weight: 385 pounds
  • Tank volume: 3.96 gal.
  • Runtime: 4-hour run time at 1/2 load
  • Warranty: not specified

More features: durable, fully welded 1-1/4″ steel frame, electric starting with the battery

OVERALL RATING: 8.7 out of 10

A powerful generator like this is a Liquid Discharge Eject Generator type revolving field. It has two poles and a self-excitation frequency measured in Hertz(Hz) of about 60Hz. It boasts a power output measured in KiloWatts(kW) of 5.5 or 5,500W. The alternating current Voltage measured in Volts(V) is rated between 110V to 220V.

Its operation is very good due to the speed at which the engine works; it boasts of an engine speed of about 3,600 revolutions per minute. Also, it comes with a direct injection system as the engine is in a vertical alignment and a four-cycle, air-cooled diesel displacement.

The starting system which is the electrical system comes with a battery for ignition purposes. The generator has Single Phase Power Factor 1. The excitation system is a controlled self-excitation. The coupling pattern is a starting shaft coupling engine. Lubricating oil is at zero degrees in summer or negative twenty degrees in winter. A standard fuel gauge with Voltmeter, AC Circuit Breaker, Engine Switch, DC Output 1V/8.3A, Low oil alert, AC socket with handle and wheel come with the purchase.

PROS:
  • 7000W peak power
  • Durable and reliable
  • Voltage between 110V and 220V

CONS:
  • It has a relatively low fuel tank
  • Very low runtime at four hours on a half load
  • Warranty is not specified

Buying Guide

When it comes to buying a diesel generator, the price is not the only determining factor. There is a whole bunch of things to consider when picking a diesel generator depending on what exactly you want to use the diesel generator for. Also, get to know the reason why you are getting a diesel generator, this could be as a result of the fuel easily obtained wherever you may be.

Pros and cons of diesel generators

There is very low maintenance cost associated with the use of the diesel generators. This is due to the fact that the diesel generators lack the presence of spark plugs and carburetors. This means no spark plugs to replace as well as no carburetors to rebuild. The major maintenance required for the diesel generator is the oil change and if done regularly will make your diesel generator last very long without any major maintenance being required.

It is also observed with diesel generators that they tend to outlast the gasoline generators when performing the same amount of work. They do the same workload and do not burn as much fuel as the gas generators. The fuel itself is also lower priced when compared to gasoline and propane fuel.

In terms of a lifetime, the diesel generator is much longer lasting than the gasoline generator. The typical gasoline generator will last approximately 1000 hours if that much. However, the diesel generator will last 30,000 hours on average without requiring a major overhauling. The diesel generator is built to withstand pressure and run at half the speed of the gasoline generators that are built mainly for intermittent usage.

ds7000q  8 1024x1024 imageDiesel fuel is also much better to store than gasoline. It is flammable, but it is not as great a risk as gasoline can be explosive. The exhaust of the diesel engine is, in fact, more visible, and this is considered one of the major downfalls of diesel as a fuel. However, if the diesel generator is properly maintained, there will be no need to be concerned as the exhaust will be minimally visible only when the generator is pressured under load changes that are severe.

Diesel can be very noisy, and this is considered to be a great downfall of the diesel system. This is usually one of the reasons homeowners tend to opt for gasoline generators. The gasoline generator is much less noisy than the diesel generator, and therefore there is no need for the generator to be placed far away from houses. There are other options available now such as soundproof enclosures that can assist with this issue.

Another consideration is the initial costs involved in setting up the diesel generator. This is usually quite a bit higher than the gasoline generator. It can be seen however that the diesel generator costs, when compared over a few years, is much less than the gasoline generator.

The choice of whether to opt for a diesel or gasoline generator can be assessed in terms of usage. If the generator is to be for intermittent use, a gasoline generator may not be a bad purchase, but overall it is considered that the diesel generator is more economical. The pros of the diesel generator by far outweigh the cons making it the better buy.

What to look for in an ideal diesel generator?

As we mentioned above, the major features of diesel generators are pretty much the same as other generator types. Let’s discuss them in more detail.

generacgp55005500wattportablegenerator l imagePowerful Engine

The power of the engine of any diesel generator is to be noted because of the amount of load the engine can carry depends solely on the power generated in the engine. In most cases where a particular diesel engine generates less power than required, it becomes so frustrating for the user and may lead to damage to the diesel generator.  A four-cycle engine is the best to consider because it allows smooth operation in diesel generators.

Output power and fuel consumption

The output power refers to the amount of power that can be supplied to the electrical appliances connected to the diesel generator. The higher the output power, the more electrical machines or appliances can be used with the diesel generator. The output power is measured in Watts, and this makes it easily noticeable in the product descriptions of diesel generators. The fuel consumption of diesel generators differs from manufacturer to manufacturer making calculating a standard measurement difficult, but in general, fuel consumption of diesel generators determines the rate at which diesel is used during machine operation. The higher the load on a particular diesel generator, the higher the rate of fuel consumption as very little load does not take too much fuel. The fuel injection system into the engine goes a long way in determining the level of fuel consumption of a diesel generator.

Quiet work

Many consumers cherish the noiseless feature in a diesel generator, and this makes it necessary in some way for diesel generators to be as quiet as possible during operation. Some diesel generators come with a soundproof feature thanks to a noiseless muffler system that enables little or no noise at all during operation. Example of such a generator that has a quiet work operation like this is the DuroStar DS7000Q diesel generator.

Safety for delicate electronics

generator running imageIn power generators like the diesel generators, reduction in peak currents, heat, emissions and core loss in motors is very important to the lifespan of diesel generators. To achieve this, a THD value is given to diesel generators after rigorous testing and measurements. So, for a diesel generator, a lower THD means more safety for delicate electronics. A THD of less than 5% is best for diesel generators, and the likes of the DuroStar DS7000Q, GENERAC 6864, SIGMA 7000W have very low THDs.

Size

The size of a diesel generator varies depending on the structure of the generator and the manufacturer. Know how much space you have before getting a diesel generator so as not to have any issues with space. The DuroStar DS7000Q and SIGMA 7000W take more space compared to the Generac 6864.

Warranty

The warranty of products depends on the manufacturer. Warranty allows you to return a certain good back to where you purchased it from if it develops any fault within the warranty period. Warranty could go for as long as a year or even more in some cases.

Extra features

The extra features in a diesel generator are the special stuff included in the diesel generator by the manufacturer. The SIGMA 7000W comes with extra feature which includes: durability, fully welded 1 1/4″ steel frame, electric starting with battery. The DuroStar DS7000Q comes with an extra feature which includes: remote start and/or electric start, oil alert automatic shutdown, volt meter, circuit breakers, low fuel indicator. The Generac 6864 comes with an extra feature which includes:  durability and a fully welded 1-1/4″ steel frame.

FAQ

All installation, repairs, and maintenance should always be in accordance with the instruction manual made by the manufacturer or rather still if you are having complications, call an expert.

The fumes emitted by the diesel generator which contain deadly and poisonous gases such as carbon monoxide (CO) are very dangerous and deadly to the human health. The exhaust systems should be installed by professionals, so proper installations can be made, and there should also be very good ventilation to make sure there is no blocking of the flow of the air in the cooling system. The direction of the exhaust pipes must also face the direction where people are not concentrated.

The generator should be kept in a location far away from inhabited zones and from materials that are combustible.

Firstly, check whether the water tank is filled with water. During winter, be sure to check the antifreeze level if full. After these, check for the oil level, fuel level, and the radiator water level. Make sure to add the right amount if the level of any is lower than the standard level. Check if all electrical connections are properly connected. Also, be sure there is no leakage and no dirt or blockage in the exhaust. The last but not the least is to make sure the battery and voltage are normal. With all these, you are ready to start a generator.

During winter, you use a diesel generator more often than other weather conditions to keep the diesel generator warm enough. Always make sure your antifreeze level is up always. Examples of generators you could use during the winter period are the DuroStar DS7000Q due to the fact that it can run for a long time at about 12 hours on a half load. The DuroStar DS7000Q is also remote controlled which means you do not have to go outside in the winter to switch on or off. Generally, it is best the diesel engine is in check all times.

It is advisable to use a diesel engine what is fully covered to avoid electrocution and damage to the electrical parts of the diesel generator. The diesel generator should also be kept in a location where rain does not affect too much to reduce the level of water damage, and you might as well get a canopy tent to act as a shelter for the diesel generator. This is still the best practice so far. In the long run, allowing a diesel generator to be beaten by rain would cause severe damages as well as spoiling the surface of the frame on the diesel generator.

To calculate the total amount of power you need when planning on getting a diesel generator. Lookout for the different power rating of the electrical installations in the building you want to supply power generated from the diesel generator to. Check for the power rating of your machines, air conditioners, water heaters and much more. Make sure to get a rough estimate, and with this rough estimate, you can look for a diesel generator with an output power rating above the total power or rough estimate of power needed you calculated. Make sure you purchase a diesel generator well above your total calculated power rating to allow installations of other electrical gadgets in the future.

Always make sure to double check your diesel generator before switching it on always. This helps you keep track of what and when anything happens to it thereby making troubleshooting easier. If your diesel generator refuses to start, make sure to check if the battery is properly connected because without no battery source (for diesel generators that have a battery power source), no ignition. Your diesel generator could go off suddenly during operation, keep calm. A major cause of sudden stop in diesel generators is overheating and oil leakage. Make sure to check if the water in the water tank to is filled up. Also, your diesel generator could make funny sounds or start current fluctuation. It could just be that you are running out of fuel, check the indicator level to be sure about this.

Our Verdict

Overall, the DuroStar DS7000Q comes in first place due to the fact that it has some awesome cool features, not too expensive and as well generates enough power. It makes us list it as the best all round. The SIGMA 7000W takes an overall rating of 8.7 with good enough specifications and features. Coupled with the fact that it is not expensive, it caters to all other areas where it does not play too well. We made the SIGMA 7000W our budget pick.  Finally, the Generac 6864 boasts of an overall rating of 9.0 with high durability and a very long runtime at 32.4 hours with a half load. However, the price makes it not budget friendly.

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