Best Diesel Generator Reviews

Updated October 14, 2020

A generator is a useful bit of kit to keep your home running if storms, bad weather or supplier issues cut off your mains supply. Having a generator ready to take over the running of your household power minimises the interruption to critical appliances such as your refrigerator and freezer, as well as basics such as your lighting.

If you’re looking for a back-up solution to have on hand if you lose mains power, you may be weighing up which is the best home generator for your needs. Your main two choices are petrol or diesel, each with their own pros and cons.

If you’re considering a diesel backup generator, we’ll guide you through some of our top choices and explain some of the main points to consider when deciding on the best generator for your needs.

Best Diesel Generators

#PREVIEWProduct
1 Generac 6864 Diesel Powered Portable Generator Generac 6864 Diesel Generator
Hide other buying options

2
Best For Higher Budgets
2Cummins Onan Diesel Generator
Cummins Onan Quiet Series Diesel RV Generator
Best For Higher Budgets
Cummins Onan Diesel Generator
Hide other buying options

3
Best For Low Budgets
3Pulsar PG7000D Diesel Generator
Pulsar PG7000D Diesel-Powered Generator with Electric Start
Best For Low Budgets
Pulsar PG7000D Diesel Generator
Hide other buying options

4 DuroStar DS7000Q Portable Diesel Generator
Best Overall
DuroStar DS7000Q Diesel Generator
Hide other buying options

1. Generac 6864 Diesel Generator

Highlights
  • Sturdy steel frame with lifting eye for easy transport.
  • True Power Technology for smooth operation of sensitive electronics and appliances.
  • 120V or 120/240V voltage selector.
  • Air-cooled direct injection diesel engine.

This is a sturdy and heavy duty diesel generator with a steel frame. The 12 gallon tank means that it has a really impressive run time of over 32 hours, with single touch electric start for easy start-up. 

The 5000 running watts will power multiple tools if you’re using this on a job site, or cover all or most of your needs if you’re using this for emergency power. It has a good selection of outlets, and there’s less than 6% total harmonic distortion meaning your electronics will run smoothly. Overall, this is a good all-rounder with great runtime, though it’s a shame the battery needed to start it up has to be bought separately.

Specifications

Size:
33.1 x 22.5 x 25.6 inches (841 x 570 x 650 mm)
Voltage:
120/240V
Wattage:
5000 (AC Rated Output Running Watts)
Output:
5000 running Watts
Power Source:
Diesel

Pros

  • 12 gallon fuel tank for an impressive run time of over 32 hours at 50% load.
  • Single touch electric start.
  • Durable, thanks to the welded steel frame.
  • Hour meter to track maintenance intervals.

Cons

  • Does not come with the battery needed for the electric start.
  • Heavy, needs a wheel kit (not supplied) to move it around.

2. Cummins Onan Diesel Generator

Highlights
  • Computer-controlled constant speed operation.
  • 10,000W output.
  • Sound insulated cabinet and muffler to reduce noise.
  • Self-diagnostic capabilities to simplify troubleshooting.
Best For Higher Budgets
Cummins Onan Quiet Series Diesel RV Generator

If you need a quiet but powerful diesel generator for your RV, this is a solid choice. The 10,000W output is enough to power three rooftop air conditioners with capacity left over to run lights and appliances. 

The constant speed operation adjusts the engine speed to match the load demand, minimising the noise level. This generator is quieter than National Park Service requirements,  with sound-controlling housing. Accessible service doors and self-diagnostic capabilities simplify maintenance and trouble-shooting.

Specifications

Size:
42 x 25 x 27 inches
Voltage:
120/240V
Wattage:
10,000W
Noise Level:
68dBA (at 10 foot, half load)
Output:
10,000W
Power Source:
Diesel

Pros

  • Ideal for diesel-powered motorhomes.
  • Meets National Park Service sound level requirements (less than 60dBA at 50 feet).
  • High quality, pure Sine wave electrical output.
  • Quick and easy starting, with automatic timed glow plugs.

Cons

  • Power output decreases with temperature increases and elevation gain.
  • Battery for electric start not included.

3. Pulsar PG7000D Diesel Generator

Highlights
  • Closed frame design to reduce noise, and wheels for mobility.
  • Durable 10 HP vertical diesel engine.
  • Can run for up to 9.5 hours between refills.
  • Five outlets ranging from 120V to 240V to 12V.
Best For Low Budgets
Pulsar PG7000D Diesel-Powered Generator with Electric Start

This is an electric start generator with battery back-up for easy starts. It can produce up to 7,000 peak watts thanks to the durable 10 HP vertical diesel engine, enough to provide power for your RV or as a backup supply for your home. 

There are five outlets of different types, so you can power a range of tools, devices and appliances. Despite the relatively small 4 gallon tank, it is fuel efficient, lasting 7 hours on a full load (9.5. On a half load).

Specifications

Size:
38 x 32.5 x 22 inches
Voltage:
120V
Wattage:
7,000 peak watts / 5,000 running watts
Noise Level:
70dBA
Output:
7,000 peak watts
Power Source:
Diesel

Pros

  • Can run for up to 9.5 hours between refills.
  • Noise level is less than 70dB.
  • Range of outlets can be used for a variety of tools and appliances.
  • Maintenance free battery included.

Cons

  • Four gallon fuel tank is relatively small.
  • Has wheels, but is heavy to move around.

4. DuroStar DS7000Q Diesel Generator

Highlights
  • Produces 6,000 peak watts of power, constant of 5,500 watts.
  • Dependable 4-stroke single-cylinder direct injection engine.
  • Oil alert automatic shutdown for low oil pressure.
  • Portable, thanks to the wheel kit.
Best Overall
DuroStar DS7000Q Portable Diesel Generator

This diesel-powered generator has a variety of outlets to supply power to home appliances, and two twist-lock outlets for high-powered tools. 

The generator can produce 6,000 peak watts and a constant of 5,500 watts. The engine uses a direct fuel injection system for low fuel consumption and it can run for 12 hours at half load. 

The fully enclosed frame, super quiet muffler and soundproofing combine to help reduce engine noise. This generator offers both an electric start and standard recoil start, making it very simple to get going.

Specifications

Size:
37.8 x 22 x 30.3 inches
Voltage:
120V / 240VAC & 12VDC
Wattage:
6,500 peak watts / 5,500 running watts
Noise Level:
78dB
Output:
6,500 peak watts
Power Source:
Diesel

Pros

  • Remote start and/or electric start for ease of use.
  • 12V, 120V and 220V outlets.
  • Muffler and soundproofing to reduce engine noise.
  • 12-hour run time at half load.

Cons

  • Relatively small fuel tank capacity (3.8 gallons).
  • Very heavy.

Diesel Generator Buying Guide

Type

If you’ve not previously purchased a diesel generator, you’ll notice lots of technical details that can be hard to decipher. We’ll try to guide you through some of the choices you’ll need to make, beginning with the type of generator that’s most suitable for you.

Portable Diesel Generator

A portable diesel generator can be put wherever you need access to power. This could be a temporary worksite (such as a construction site), campsite, or kept for emergency use if your home power supply is interrupted. They may have a wheel kit so they can be manoeuvred into place and have a smaller capacity than a larger, standby generator.

Standby Diesel Generator

A standby generator is designed to be permanently installed in one location, and connected to the main electrical system. They can be set up to automatically kick in if the main power supply fails. This can be very important in certain locations where maintaining a constant supply is vital, such as in hospitals or manufacturing locations. They have a high capacity and are larger in size.

Diesel Generator Setup

The process of setup for the generator you purchase will vary by model. Most smaller generators supplying around 10kW for domestic or small worksite use are portable and are simply moved into place wherever they are needed at the time.

If you are installing a generator as a standby for your home or business, you should follow the exact instructions detailed in the manufacturer’s operating manual. 

Applications

The generator you choose will depend on how you want to use it, as this will determine the amount of power it needs to generate, how portable it needs to be and other variables. 

For RV and Camping

Generators for RV and camping use to power anything from a refrigerator to air-conditioning units. If this is your intended use, then the portability of the generator is likely to be a key consideration. Noise is another factor, especially as some campsites and locations such as National Parks may have noise restrictions to prevent disturbance for wildlife, or for other campers.  

For Home Backup

Some people like to keep a generator at home in case the main supply cuts out. A whole house generator can connect to your home’s electrical system to kick in when needed. The size of the generator you’ll need depends on the size of your home and what it will need to power. As a home backup generator will remain in one location, the size and weight are not as important. 

Diesel Generator Efficiency

How efficient a diesel generator is will determine how long it can run on a tank of fuel. If you are looking for a generator which is compact in size, it will have a small fuel tank. An efficient generator should give you a good running time even if the tank capacity is only a few gallons. 

Noise Level 

The noise created by a generator is a particular consideration if you’re using it to camp, but it can be important no matter what the intended use. The noise level of a generator is measured in decibels (dB). It’s worth knowing that for every 10 decibel increase, the noise is 10 times louder. So, for example, a 70dB generator is 10 times louder than a 60dB generator. A product with a decibel reading around this level would be considered a quiet diesel generator.

There are some products which are termed as a silent generators. These are not completely silent but usually have a case to muffle noise to an unobtrusive level.

Wattage

It’s important to select a generator that’s the appropriate wattage for your needs. Your generator needs to be able to power all of the appliances you’ll connect to it without overloading, which is the most common cause of generator failure. You can work this out by adding up the wattage of each individual item you want to power, remembering to add a buffer of around 20%. 

5kw Diesel Generator

A 5kW generator should be sufficient for camping, for home backup of your key appliances such as refrigerators or for occasional jobs or a hobby that needs power tools.

10kw Diesel Generator

To power more of your home appliances from a backup generator, a 10kW generator, the top end of the ‘small generator’ market may be a better choice for you. 

15kw Diesel Generator

A 15kW generator is a larger product, often used by businesses or on worksites. 

20kw Diesel Generator

A 20kW diesel generator can provide power for an industrial site, for a full home backup or for a construction worksite.

30kw Diesel Generator

A 30kW generator is mainly aimed at commercial use, to power a worksite or to provide a backup option for an industrial facility. 

100kw Diesel Generator

A 100kW generator is large and heavy duty, for commercial and industrial use. It far exceeds the needs of a domestic household. 

Size

The size of the generator you opt for is another factor in your overall decision making.

Large Diesel Generator

A large diesel generator will be too big and weigh too much to be moved around without machinery. It therefore needs to be kept in a fixed position. Large generators are typically those for commercial use or standby domestic generators.

Small Diesel Generator

If you want a generator to take camping or to move around your property to use for activities such as hobbies and  home improvement projects, it’s best to look for a more compact generator. Even smaller generators can be very heavy, so a model with wheels will be more portable.

Frequently Asked Questions

Q: How Does a Diesel Generator Work?
A:

A diesel generator effectively takes energy in one form – from diesel fuel – and transforms this into a different type of energy – electricity.

A generator works on the principle of electromagnetic induction, discovered by Faraday in the early 1800s. He found that electric charges could be induced by moving an electrical conductor in a magnetic field. The movement creates a difference in voltage between the two ends of the conductor, such as a wire, causing electrical charges to flow and generating electric current.

A diesel generator produces electricity by burning diesel. Diesel contains chemical energy, which the generator converts to heat and force, known as mechanical energy, through a process of combustion.

This mechanical force helps rotate the alternator in the generator, creating the magnetic field for the electromagnetic induction principle that turns mechanical energy from the fuel into electrical power.

Q: How to Prime a Diesel Generator?
A:

Priming a diesel generator is important to keep all the vital parts such as the engine and fuel lines free of air. If air gets into these components, it can cause generator outages and even failure. Many modern models do come with a primer, but if yours doesn’t, you can complete the process yourself.

You’ll first need to open the fuel supply valve, to let diesel flow through the system. Then, starting with the fuel filter, open the fuel valve and let diesel and any air flow out from it. You can then connect a priming pump to let any bubbles and diesel be sucked away. Replace the valve ensuring it’s secure.

You should repeat the same process for all filters, each time resecuring any valves once you’re finished.

Our Verdict

A diesel generator is a very useful bit of kit to have at hand, with multiple uses from home backup to camping, or powering tools for improvement and construction projects. The appropriate size for you will depend on the intended use and how portable you need the generator to be. 

For a great all-round option, we rate the Generac 6864 Diesel Powered Portable Generator. The construction is sturdy and heavy duty and the runtime of over 32 hours is very impressive. We also like the multiple outlets and the easy electric start. The minimal harmonic distortion for smooth running of your electronics sealed the deal for us, securing our vote for the title Best Diesel Generator.