3 Best Portable Diesel Generators of 2025 – Reviews & Top Picks
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Pete Ortiz
- Last updated:
Diesel generators are popular for a few reasons. They require less maintenance than their counterparts and have better fuel efficiency. However, anyone who has been around a running diesel engine, either from a truck or other small engine, knows they have a distinctive sound and a recognizable exhaust smell.
That clicking sound can almost drive you crazy, and the odor will give you a headache. However, new technology and innovation have made the diesel engine more appealing. To help you decide which model is the best, we have reviews of three remarkable, portable diesel generators.
A Quick Comparison of Our Favorites in 2025
| Rating | Image | Product | Details | |
|---|---|---|---|---|
Best Overall
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Generac 6864 Diesel Powered Portable Generator |
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CHECK PRICE |
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Cummins Onan Quiet Series Diesel RV Generator |
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CHECK PRICE |
Premium Choice
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Onan 8.0HDKAK-1046 Quiet Diesel Generator |
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CHECK PRICE |
The 3 Best Portable Diesel Generators
1. Generac 6864 Diesel Powered Portable Generator – Best Overall
Durability and power are what sets the Generac 6864 Diesel Powered Portable Generator apart from the rest of the field. That is why we made it our best overall pick. It has 5,500 starting watts and a 12-gallon fuel tank that runs for more than 30 hours. Because of its reliable diesel engine, you will enjoy its long life with less maintenance.
There are many features the Generac packs into this 254-pound portable generator, and at first, you might wonder how to transport such a weighty machine. It is recommended to purchase the wheel kit to make it easier. The True Power Technology 435cc industrial-grade engine has fuel-efficient idle control and air-cooled direct injection.
True Power Technology means that you get less than 6% total harmonic distortion for smoother operation of sensitive electronics, tools, and appliances. To get the Generac started, you can use the pull start, which has been known to be difficult. However, we think purchasing the battery is necessary. The battery is a 330 CCA battery, and it will take care of operating the single-touch electric start. It is also the only way that the fuel cutoff will work.
Your generator comes securely cradled in a 1¼-inch steel frame that is fully welded and solidly constructed. The frame has a fully integrated lifting eye that allows you to transport the generator or secure it easily.
- 12-gallon fuel tank
- Single-touch electric start
- Long run time
- Fuel-efficient idling
- Industrial grade
- Difficult pull start
- Loud when operating
- Weighs 254 pounds
- Wheels and battery purchased separately
2. Cummins Onan Quiet Series Diesel RV Generator
The Onan Quiet Series Diesel RV Generators are the heavy-duty choice among diesel generators. They produce less noise and vibrations and operate below the threshold of National Park Service requirements. In fact, they are so quiet that they are almost quieter than their gasoline engine counterparts. The Onan 10HDKCA-11506 is pricier but produces 10,000 watts of power, which is enough to run three rooftop air conditioners.
This feature-packed machine has enclosed cooling, a muffler, and intake systems with a heavy-duty air cleaner. Its constant speed operation delivers pure sine wave electrical output, so you can be sure your appliances are protected. It produces both 120 and 240 volts for a variety of applications. The generator is equipped with a USDA spark arrestor and a maintenance-free electronic governor for safety.
Equipped with a large fuel tank capacity, it has an average fuel consumption during run time. On the downside, the Onan generator is extremely heavy, weighing 785 pounds. It’s not something that you would consider portable.
- Powerful 10,000 watts
- Quiet operation
- Auto shutoff
- Hour meter
- Extremely heavy
- Very pricey
3. Onan 8.0HDKAK-1046 Quiet Diesel Generator – Premium Choice
The 8,000-watt Onan generator has some of the same features as its more powerful brother we previously reviewed. It’s also expensive and weighs a hefty 420 pounds. Therefore, transporting it may be difficult, and no additional accessories, like wheels, can be purchased to make it more mobile.
However, the Onan 8.0HDKAK-1046 Quiet Diesel Generatoris our Premium choice. It has a 3-cylinder diesel engine with an intake silencer and computer-controlled variable speed operation in a sound-controlled housing. This makes it quiet, and the noise is well below the National Park Service sound level requirements.
It has a digital voltage regulation system providing high-quality sine wave electrical output. The heavy-duty air cleaner, internal radiator, maintenance-free electronic governor, and bottom air inlet and outlet are additional features that make this generator shine. Also, the Onan 8000 has a USDA spark arrestor and meets the U.S. EPA and California emissions standards.
As mentioned at the beginning, it is heavy and difficult to transport, especially if you are using it for your RV, but it will operate two 15,000 BTU air conditioners and several other appliances, so you may still consider taking it on the road with you.
- Extremely quiet
- Computer-controlled variable speed
- Easy maintenance
- USDA Spark arrestor
- 000-watt output
- High Priced
- Very heavy
- Difficult to transport
Buyer’s Guide – Choosing the Best Portable Diesel Generator
Next, we’ll discuss the factors to consider when shopping for the ideal diesel generator.
Price
The price may be your first consideration since generators are expensive machines. Before shopping online or visiting retailers, develop a budget you can work with. Then, you can examine several brands within your price range.
Purpose
If you don’t plan on using a generator to power a household of appliances and devices, you can buy a generator that produces less power than heavy-duty machines. However, if you need a generator to power air conditioners and other power-draining appliances, you’ll need a model that produces top-tier power.
Power
You’ll need between 7,000 to 9,000 watts to run household appliances such as refrigerators, computers, TVs, and other small appliances. Your generator should also have a digital voltage regulation system that will produce high-quality sine wave electrical output to prevent damaging your appliances.
Fuel Tank Capacity
When operating your generator, consider how large your fuel tank is and the length of time that the generator can run on a tank of gas. The larger the tank capacity, the longer you can run your generator continuously, which makes it more convenient.
Size & Style
Choosing a portable generator involves researching generators of all sizes and styles. We reviewed diesel models that varied in size, power, and output. While making your decision, ensure you are looking at all of your options. Have a firm grasp of your needs so you don’t fall short on power.
Conclusion
Our choice for the best portable diesel generator overall went to the Generac 6864 Diesel Powered Portable Generator. Although it does not have the power of the other two generators, it has many vital features that make it a solid choice for any home or RV. It has 5,000 watts of power, a single-touch electric start, and a long fuel-efficient run time.
The Onan 8.0HDKAK-1046 Quiet Diesel Generator was our premium choice because of the 8,000 watts of power, the light maintenance it may require, and its quietness. It costs significantly more than the Generac, but its long-lasting capabilities and performance may make up the difference in cost. It’s not quite a portable generator because of its 420 pounds, but you will find the rest of its features to be above standard. We hope you enjoyed reading our reviews and find the ideal portable generator for your needs.
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