Diesel Generator Buyer's Guide

Diesel Generator Buyer's Guide

When to Use Home and Commercial Diesel Generators

By  | Generator Product Expert
By  | Generator Product Expert

Big Rig TruckDiesel is synonymous with power in our culture. Big rigs, smoke, and burly truck drivers come to mind, but did you know that this same power is used in generators?

A commercial or home diesel generator can provide higher efficiencies and improved dependability in certain applications. Our diesel generator buyer’s guide will explain just what makes this fuel so powerful and how to make it work for you.

What is Diesel?

Diesel is a liquid fuel that ignites in an engine by heat and compression instead of spark and is used in various heavy pieces of equipment, like generators.

Compared to gas, diesel is oilier and has a higher boiling rate. By volume, diesel contains between 10-15% more energy, which translates to greater power and efficiency.

How Does a Diesel Engine Work?

A generator diesel engine operates using the same four-stroke principles as a gas engine but differs in the combustion process:

How does a diesel engine work

  1. Intake Stroke: Air enters the engine cylinder, pushing the piston down.
  2. Compression Stroke: As the piston moves back up, it compresses the air.
  3. Power Stroke: When the piston reaches the top of the cylinder, a fuel injector injects diesel into the super-compressed air, causing spontaneous combustion (without using a spark plug) which forces the piston down.
  4. Exhaust Stroke: The piston moves back to the top of the cylinder, pushing exhaust gases out.

The reason diesel generator engines don’t require a spark plug to ignite the air/fuel mixture is because the air is compressed much more than in a gas engine. The tighter the air is compressed, the hotter it gets.

The level of compression is measured by the compression ratio. An engine compression ratio is the ratio of the maximum to minimum volume in the cylinder. In other words, how much space is in the cylinder when the piston is at the very bottom versus how much space is there when the piston is at the very top.

Diesel EngineMost gas engines have compression ratios of between 8:1 and 12:1. Diesel engines have compression ratios as high as 20:1, which compresses the air into such a small space that it becomes hot enough to combust without a spark plug.

The other big difference between gas and diesel engines is in how the fuel is added. In carbureted gasoline engines, the intake valve releases air/fuel into the cylinder as a mixture. Diesel engines, like fuel-injected gas engines, inject the fuel right before the power stroke when the air has been compressed.

Because the air is packed together so tightly at this point, the fuel molecules can react with more oxygen, resulting in more power. This also results in greater fuel efficiency than in a gas engine.

Is Diesel Better than Gas?

With its higher power output and greater efficiency, a diesel generator is better suited for high-demand or remote applications than gas. 

Diesel generators are larger and more robust than gas generators in order to handle the higher power loads. These engines are almost always liquid-cooled rather than air-cooled.

In terms of price, diesel generators tend to cost more, mainly due to their larger, liquid-cooled engines. Less overall maintenance is required for diesel generators, but, when it is required, tends to be more expensive.

Diesel Generators Gas Generators
 Diesel Generator  Gasoline Generator
More Power Less Power
Higher Fuel Efficiency Lower Fuel Efficiency
Larger More Compact
Mostly Liquid-Cooled Mostly Air-Cooled
Less Overall Maintenance More Overall Maintenance
More Expensive Less Expensive


Diesel Commercial Generators

Commercial applications tend to use diesel generators more often than residential ones. They are common in the mining, construction, marine, and telecommunications industries due to their rugged build and power.

The fuel and maintenance savings are also popular among commercial owners, who often put their generators under the strain of heavy, long-term use. A diesel generator is the undisputed better option for commercial applications.

Home Diesel Generators

portable diesel generatorAlthough much less common, home standby diesel generators can benefit homeowners for all the same reasons. 

Homeowners have often stayed away from diesel because they associate it with toxicity and noise. However, newer diesel engines are becoming quieter, and their toxic emissions are comparable to those of gasoline.

Diesel is also less flammable than gasoline and safer to store. During emergency situations like hurricanes or earthquakes, diesel may also be easier to obtain--and that's when you would need your generator the most.

Finally, remote homeowners who aren't connected to a natural gas line might need a diesel generator. There are even smaller units for those who would like a portable diesel generator, such as hunters in a lodge.

Power in Your Hands

Diesel generators give you more available power to get the job done, and you don't even have to be a truck driver.

If you have any questions about picking a diesel generator, please give us a call at 1 (800) 800-3317.

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