Diesel Generators: Everything You Need to Know

Why are so many American homeowners and renters purchasing diesel generators for the first time?

It's because more extreme weather events are showing an increased number of us how debilitating a power outage can be. If you've been through one without a generator, you know it's a lot more than losing electricity. Your mobile devices die, you have no hot water, your food spoils — and that's just the tip of the iceberg.

Investing in the right generator, however, can mean a steady stream of back-up power to make your next outage less harrowing. But what's the right generator?

For many, a diesel-fueled generator is the way to go.

Diesel generators are renowned for their reliability and their longevity. They're safe and relatively inexpensive to purchase, power and repair compared to many other types of generators.

Before you find a reputable generator dealer in your area, use AlltimePower's free Backup Power Calculator to determine the electrical capacity you need. Then take a few minutes to read this post to find out if diesel generators are right for you.

What is a Diesel Generator?

Let's start by learning what a diesel generator is. A generator is an internal combustion engine similar to what you'd find under the hood of a car. It converts the energy stored in fuel — in this case diesel fuel — into mechanical energy by causing a piston to rotate. That mechanical energy is next converted into electrical energy. That's why your generator needs to be connected to your home's electrical wiring to power it.

What makes diesel different from other fuels such as gasoline?

In a gasoline engine, the fuel (gasoline) is allowed to mix with the air being compressed by pistons. A spark plug ignites that mixture and that ignition is what creates the energy.

A diesel engine is different for two main reasons. First, the air is compressed alone — without the fuel (in this case, diesel). This allows for a greater level of air compression which creates greater fuel efficiency and lower fuel costs.

Second, more compressed air equals hotter air. It's so hot, in fact, that ignition is automatic when the diesel fuel is added. This means a separate spark plug isn't necessary and that saves a lot of future money in maintenance.

Diesel engines are powerful and efficient. They're found in trains, trucks, boats, buses and some cars. Generators that use diesel fuel are the most common products on the market.

Diesel Generators are Reliable

Consumers appreciate diesel-powered generators because of their reliability. In fact, Rudolf Diesel invented the diesel engine in 1878 because gas engines were horribly inefficient. They only used about 10% of the fuel they burned and Diesel believed he could do better.

And that's what he did. To this day, diesel generators are considered the most efficient and cost-effective choice. They're built to provide significant amounts of power for a long time.

Superior fuel efficiency is a diesel generator's major advantage. They can run much longer than other generators of the same size thanks to their excellent design and the efficiency the compressed air allows.

It should be no surprise industrial plants and hospitals rely on diesel-powered generators to keep essential operations running when the power grid fails. That same desire for reliability is the reason more homeowners choose diesel over any other fuel source to power their generator.

The supply of diesel fuel is also reliable. They can be found in containers for purchase at locations across the United States. Gasoline, too, can be found at any gas station. But gas stations are notorious for being overrun during the same storms that can knock out the electrical grid.

Natural gas is another common source of power for generators. Many city homes include piped-in natural gas, making a natural gas generator convenient.

But recent hurricanes in Louisiana, and frozen conditions in Texas, damaged the natural gas infrastructure. Depending on natural gas for your generator has risks that reliable diesel-powered generators avoid.

Diesel Generators are Affordable

Cost is a major factor for many consumers purchasing a generator. You can find more about calculating the generator costs your home requires here.

The two cheapest options are natural gas generators and diesel generators. The upfront costs of a diesel-powered generator is higher than its natural gas counterparts.

But that doesn't mean diesel generators will cost you more in the long-term.

This is why many buyers say the efficiency — or high energy density — of diesel makes it a superior option. Simply put, diesel generators get more power per the amount of fuel provided. Diesel-powered generators also tend to reach peak effectiveness before other generators. This is because their inbuilt cooling component helps handle the heat produced without needing coolant, water pumps, radiators or temperature gauges.

All this means diesel generators run longer. The longer they run, the less you pay to refuel them.

Those savings aren't insignificant. Experts have calculated that diesel-powered engines have 30-50% lower fuel costs than gas engines. As fuel prices rise, the cost savings a diesel generator provides in the long-run can eclipse the higher set-up costs at the outset.

Maintenance is Also Easier with Diesel Generators

The efficiency of its fuel isn't the only factor that makes diesel-powered generators cheaper. Remember how diesel fuel doesn't require a spark plug to ignite like with a gasoline engine? Well, fewer parts to replace means less money spent on maintenance over the generator's lifetime.

Diesel generators won't keep you busy with tune-ups and repairs. Besides needing the occasional oil change and preventative maintenance check-up, they are the closest thing to a set-it-and-forget-it solution to your home's back-up power needs.

A gas generator, in contrast, burns hotter than a diesel unit. That heat means more wear and tear, more maintenance and ultimately a shorter lifespan. In addition to oil changes, gas generators will need periodic replacement of air-cleaner elements, spark plugs, ignition points, rotors, distributor caps and plug wires. It will also likely require carburetor adjustments and overhauls, as well as general tune-ups.

A diesel generator is more sturdy and reliable. It has fewer parts to replace. It requires far less maintenance and runs reliably for longer. On average, diesel units can operate three times longer than their gas-powered counterparts.

Preventive Diesel Generator Maintenance Can Mitigate Costs

It is worth noting, however, that after-sale services and parts replacements for a diesel generator can be expensive. There are some simple things you can do to minimize those costs.

First, have your generator serviced regularly by a professional to find any issues before they become an expensive problem.

Second, diesel generators must be run at least once per month to avoid breakdowns.

And, finally, you'll want to make sure your diesel fuel remains at a high quality. Gasoline may not be as energy dense as diesel, but it is more highly refined. Diesel is a heavier fuel and is more prone to going "off-spec." Additives can keep your diesel fuel more consistent.

There are two key times you might consider using an additive.

Consider an additive if your diesel sits in storage too long

If your diesel fuel has been stored in your fuel tank for longer than 30 days you might consider an additive. This isn't uncommon given the unpredictable nature of natural disasters and power outages.

Without the proper additives, pure diesel doesn't have a long shelf life. It can degrade when exposed to moisture, certain metals and alloys, high temperatures and even oxygen. The diesel will begin to oxidize, causing hydrocarbons to react with oxygen in the tank. This — along with the accrual of dirt and dust — can create deposits that can damage fuel lines, fuel injectors and other system components.

Sometimes the diesel you purchase may already include additives. It's important to research products or talk with diesel distributors to ensure your diesel generator is being fed the quality fuel it needs.

Winter challenges for your diesel generator

There are some challenges to using diesel fuel as the temperature drops. Naturally occurring paraffin wax in diesel begins to crystallize around 32 degrees Fahrenheit. At 15 degrees Fahrenheit (-9.44 °C), it gels. This clogs tanks and fuel filters.

Fortunately there are additives for this, as well. Products like Diesel 911 can reliquify gelled fuel and de-ice frozen fuel filters.

Another issue on cold days is caused by a diesel engine's design. Your diesel generator ignites when the compressed air gets so hot even a small injection of mist-like fuel causes combustion. When the temperature falls below 32 degrees Fahrenheit, however, the compression of the air might not cause it to get hot enough to ignite.

Generator block heaters and glow plugs can be a good investment to make if you purchase a diesel generator. They help ignite the generator fuel in the engine even when outside temperatures are low.

If you live in a place that is frequently cold, a diesel-powered generator has its challenges. These can be overcome in a way that remains more cost-effective than other back-up power options.

Diesel Generators are Relatively Safe

Gasoline-powered generators require frequent refueling to stay running. The refueling process exposes you to gasoline, and gasoline is flammable.

Diesel generators, on the other hand, require less refueling because diesel fuel is more energy-rich. The less refueling that takes place, the smaller the chance of disaster.

Diesel fuel is also less flammable than gasoline, and the absence of a spark plug eliminate the risk of freak fires.

Natural gas is extremely flammable. It can be a serious fire hazard in the unlike event a pipeline bursts,

Aren't Diesel Generators Noisy?

Diesel generators are notorious for being loud when they operate. If you were living in a heavily populated area, neighbors would likely complain about the noise pollution of your generator unit.

Loud diesel-powered generators are now a thing of the past. Modern models are more quiet, in part because they require less power to run.

Better design has also reduced generator noise. Some come with a noise-insulating canopy or employ a muffler. Others utilize vibration-isolation mounting to reduce the vibration on the machine. Not only does this address the noise — but reducing vibrations also mitigate wear and tear and extends the life of the generator.

The Environmental Impact of Diesel Generators

Diesel burns less cleanly than natural gas, gasoline and propane. Propane, in particular, is considered to be an energy-efficient "green fuel."

But the disadvantage of a propane-powered generators is three-fold.

  1. Propane isn't as easily accessible as gasoline and diesel. Even the propane tanks available at gas stations cost more than propane from a specialized provider. Those providers are often located outside city limits, which means you could be driving a long way to restock your generator's fuel source.
  2. A well-maintained diesel generator can last thousands of hours more than an equally maintained propane (or natural gas) generator.
  3. Propane is a third less energy-dense than diesel fuel. You'll need to keep more on-hand in an emergency and the cost of refilling will be substantial.

Renewable energy sources like solar and wind are the most environmentally-friendly generator options. Relying on these forms of energy for your back-up power needs can be risky. They are currently less efficient than diesel fuel, and they require certain weather conditions to be effective.

Improved technology has allowed diesel generators to become more sustainable. Diesel generators have been invented that emit 26 times less particulate matter than those manufactured even 10 years ago.

New environmentally-friendly hybrid fueled generators can run on a mix of diesel and a renewable energy source like solar or wind. They tend to have a higher upfront cost, but users can save money on electric bills in the longer-term. The renewable energy is stored in a battery and the diesel only kicks in as necessary.

Next Steps

Many consumers find the diesel generator to be most able to meet their back-up power needs. The energy-rich nature of diesel fuel allows generators to run longer. This is important for reliability, longevity and cost.

Advanced technology is allowing designers to address the traditional weaknesses of diesel-powered generators. They aren't as noisy or as bad for the environment as they were in the past.

Choosing a generator fuel source is only part of the equation. Once you decide on a fuel of choice for your standby generator, visit our website for a personalized assessment of your home power needs. We'll help you find the right size and capacity for your home and budget.

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