Top 5 Diesel Generators for Any Purpose – Find the Best One for You

  • Last updatedLast updated: Sep 09, 2020
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Power outages can be a huge setback. The best thing you can do is to be proactive and prepare for them. This, however, doesn’t mean installing an expensive back-up system. On the contrary, by investing in the best diesel generator, you’ll find not only an affordable option but an equally effective one. But why a diesel generator? Aside from its cost effectiveness, it’s a pretty low maintenance unit. Furthermore, it’s actually more efficient than many other types. Best of all: it has a long lifespan which makes it a worthwhile investment, don’t you think?

Is it the best option? It takes a quick look at its major features, for instance, its runtime or fuel consumption to realize it’s exactly what you need. Obviously, the one you pick will depend on your specific needs. To give you an informative review, we looked at the different generator types namely: standby and portable. We compared their power output to aid in your decision making. When buying a diesel generator, you need to be aware of the tank capacity, noise level, ease of use and maintenance, and all are discussed here.

Top 5 Diesel Generators Review 2020

Hours went into this research so that we can give you a detailed review. We went through a number of customer reviews of users who had firsthand experiences with the products. Not forgetting the expert reviews so we could get the technical information from the specialists in the industry. We’ve included a comparison table, in-detail review of each product plus a detailed buying guide. Hopefully, these will help make your selection process a swift one. Don’t regret not being prepared!

Editor's Choice

This standby diesel generator with a whopping 50 kW power output will cover all your power needs during a power outage; it’s also easy to maintain and is very quiet

Read Our Review
GenScore is our patented scoring system which helps us evaluate each of the reviewed products, from 1 to 10. The score is based on the product’s individual features, its sales stats, and buyers’ feedback.
Best Portable Diesel Generator

A great portable option, this generator will give you 5,500 surge and 5,000 continuous watts for as long as 32 hours on a single tank

Read Our Review
GenScore is our patented scoring system which helps us evaluate each of the reviewed products, from 1 to 10. The score is based on the product’s individual features, its sales stats, and buyers’ feedback.
Best RV Diesel Generator

This model covers those who’re looking for a diesel generator for an RV – it’s powerful, quiet, and fuel-efficient

Read Our Review
GenScore is our patented scoring system which helps us evaluate each of the reviewed products, from 1 to 10. The score is based on the product’s individual features, its sales stats, and buyers’ feedback.
Best Diesel Generator for Home Backup

For those who’d like to have a smaller generator with a decent power output and run time, this might be just it

Read Our Review
GenScore is our patented scoring system which helps us evaluate each of the reviewed products, from 1 to 10. The score is based on the product’s individual features, its sales stats, and buyers’ feedback.
Budget Pick

If you want a sturdy and fuel-efficient diesel generator, but are not ready to overpay this might be your best option

Read Our Review
GenScore is our patented scoring system which helps us evaluate each of the reviewed products, from 1 to 10. The score is based on the product’s individual features, its sales stats, and buyers’ feedback.

Generac RD05034GDSEEditor's Choice

  • Generator type: standby
  • Rated watts: 50,000
  • Engine: Generac In-Line, 4-cylinder, cast iron OHV
  • Fuel tank: 62 gal.
  • Runtime: up to 25 hrs. (25% load)
  • Start type: automatic/manual
  • Noise level: 65–70 dB(A)
  • Warranty: 5-year limited

Its affordable price isn’t the only reason we voted it the best standby generator on our list. If anything, we’re impressed with its user-friendly abilities. For generators to work they must meet several code requirements and be approved by the necessary authorities before they can be installed. Long story short: you don’t have to worry about that if you pick this brand which is code ready. It comes with a set of popular preconfigured options plus a range of code-driven accessories. As a result, it’ll conform to the required local codes.

A noisy generator will be the least of your worries if you invest in this model. Because of its Quiet Test mode, it runs its self-test at a relatively lower RPM. You’ll find that it’s quieter than the standard operation of most generators.

Let’s move on to design: You and the service provider can read the status and settings of the generator at any time. This is clearly displayed in real time thanks to the Evolution controller which features a multilingual two-line LCD text display. You won’t be guessing any stats – or skipping any service dates – thanks to this external viewing window.

For such a high-performance unit, it’s pretty easy to install. Not only that, but maintenance is quite simple too thanks to the removable doors. This way you’ll have easy access to fuel filling and servicing.

To top it off, it comes with a 5-year limited warranty which proves its reliability.

The only downsides are the transfer switch is sold separately and a mounting pad also isn’t included.

  • Easy to service
  • Code ready
  • Easy to install
  • Transfer switch sold separately
  • No mounting pad

Generac XD5000EBest Portable Diesel Generator

  • Generator type: portable
  • Peak/rated watts: 5,500/5,000
  • Engine: 435cc, air-cooled, 4-cycle, Vertical Cylinder Diesel
  • Fuel tank: 12 gal.
  • Runtime: 32.4 hrs. (50% load)
  • Start type: electric, recoil
  • Noise level: not specified
  • Warranty: 2-year limited (residential and commercial)

The first thing you probably want to know is how easy it is to transport right? Though heavy, moving this portable generator to the job site will be a breeze thanks to the integrated lifting eye.

How does it fare performance wise? For a unit with a 12-gallon fuel tank you can tell it offers long run time. Here we’re talking about 32.4 hours at a half-load. Impressive, right?

Its high functionality is further attributed to its Yamar LW series 435cc air-cooled direct injection. The industry high-grade diesel engine confirms why it can handle large scale operations.

With regards to its design know this: It’s built to last thanks to its 1-1/4” steel cradle which is designed for added strength and durability.

You obviously want a generator that allows for smooth operation of different tools and appliances right? The 6% total harmonic distortion offered by this diesel generator makes sure of that. Because of such an impressive harmonic distortion, you can even use it with your sensitive electronics without risking any damage.

It features a low oil pressure shutdown which ultimately means you don’t have to worry about problems regarding overheating. That again is proof of its durability.

You won’t be guessing how long your generator has been running for and whether or not it’s due for oil change. The hour meter provided ensures you’re up to date with such information to enable proper maintenance of the unit.

On the downside, it won’t run without a battery. So be wary of that.

  • Durable unit
  • Low oil pressure shutdown system
  • Easy to track maintenance
  • Doesn’t run without a battery
  • Heavy

Onan 8.0HDKAK-1046Best RV Diesel Generator

  • Generator type: standby RV
  • Rated watts: 8,000
  • Engine: 719cc 4-cycle, liquid cooled, Vertical Cylinder Diesel
  • Fuel consumption: 0.49 gal./h (50% load), 1.02 gal./h (100% load)
  • Start type: remote
  • Noise level: 66 dB(A)
  • Warranty: 3-year limited

Based on its impressive specs and reliable performance we found it deserving of the best RV diesel generator title. But to own such a powerful unit, be prepared to dig deeper into your pockets because it’s pretty expensive.

What makes it so powerful? For starters, it has an 8 000W power output. For a generator specifically designed to use outdoors, it surely can power a large number of appliances.

Any noise you hear during your camping trip won’t be coming from your generator because it’s one of the quiet ones. As you might be aware, any generator used out in nature has to adhere to the National Park sound level requirements. The Onan diesel generator is even quieter than these requirements making it the ideal model to use outdoors.

The noise is further reduced thanks to the three-point fully focalized mounting system which is designed to reduce vibration.

Apart from the sound regulations, there are also emission standards these generators must comply with. You’ll be happy to know this RV generator meets both the U.S EPA & California standards.

Any service to be performed on this unit will be hassle-free because it has maintenance points which are easily accessible.

It’s the perfect RV generator to take outdoors since it comes with waterproof connectors. There’s no telling the weather conditions you might experience out there, and this generator is designed to handle such.

For such a high priced unit, we’re only disappointed its warranty period is shorter compared to others.

  • Very quiet
  • Easy to maintain
  • Eco-friendly
  • Powerful unit
  • Expensive
  • Short warranty

Power Products Sigma JDP-7000 LDEBest Diesel Generator for Home Backup

  • Generator type: portable
  • Peak/rated watts: 7,000/5,500
  • Engine: 480cc,4-stroke, air-cooled, Vertical Cylinder Diesel
  • Fuel tank: 4 gal.
  • Runtime: 8 hrs. (50% load)
  • Start type: electric
  • Noise level: 68 dB(A)
  • Warranty: not specified

Is the Onan generator reviewed above priced too steep for you? You can opt for this portable Power Products generator which is a quarter of the price. Not to say its low cost means it’s a low-performance unit. On the contrary it actually has an impressive 7000W starting output – higher than some generators in a higher price range. When running, it produces 5500W which is still powerful enough to power a number of appliances.

Still on performance, it has quite an impressive run time: 8 hours at a 50% load. Mind you this is on a full 4-gallon tank.

You’ll also appreciate that it can run from an external fuel tank camp; a capability most generators don’t have.

With regards to noise, it’s also a relatively quiet unit. The enclosed frame makes sure of that.

The only downside worth mentioning is it’s not as advanced in terms of its operations. Unlike other generators which come with a remote start option, this model doesn’t. So be prepared to switch it on manually each time.

On the upside, it’s easy to move from one location to the next considering it’s on the heavy side. The handle and wheels allow for easy transportation.

The fuel gauge is pretty standard and it has a low oil alert feature. The last thing you need is a generator that’ll stop functioning because you didn’t know it was due for an oil change.

It’s also designed to work in both winter and summer weather so you can expect optimum performance regardless of the time of the year.

  • Low price
  • High-performance unit
  • Long run time
  • Works quietly
  • No start remote option
  • Heavy

DuroStar DS7000QBudget Pick

  • Generator type: portable
  • Peak/rated watts: 6,000/5,500
  • Engine: 418cc 4-Cycle Air-Cooled Spark-Ignition
  • Fuel tank: 3.8 gal.
  • Runtime: 12 hrs. (50% load)
  • Start type: electric, remote
  • Noise level: 78 dB(A)
  • Warranty: 3-year

Now here’s one model for those working on a budget. And yes it’s even cheaper than the Power Products generator. The only tradeoff is you might have to sacrifice savings for a little noise. With a 78 dB noise rating, you can see it’s not the quieter model. But considering it’s used in noisy environments such as construction sites, we suppose it’s not a deal breaker right?

Definitely don’t be too quick to dismiss it; There’s a reason we included it on our list of recommendations. It actually has the third longest run time of the models reviewed above: an impressive 12 hours at a 50% load.

It’s the ideal unit to use in those emergency power outage situations. With a 6000/5500W power output, you can see it’ll power a considerable number of units when faced with a crisis. The fuel tank isn’t that big as it only holds 3.8 gallons, but we reckon that’s not bad in emergency situations right?

We’re quite impressed with some of its features including the surge arrest designed to protect it from power surges.

Its all metal construction is proof of its durability. You can tell it’s built to last which is a definite plus considering the rough environments you’ll be using it in.

Your investment is protected from damage thanks to the low oil shut off functionality. The generator automatically switches off immediately when it senses the oil is low.

Moving on to the negatives, we weren’t impressed that it doesn’t come with an hour meter. Also, the exhaust hood in this unit is angled wrong so it allows water in. Hopefully, the brand can fix that in future.

  • Sturdy construction
  • EPA certified
  • Affordable
  • Durable
  • Not the quietest machine
  • No hour meter

Buying Guide

Now that you know what products are at your disposal, how about we give you a few pointers on what to look for? We’re certain after going through this buyer’s guide you’ll realize which generator serves your purpose best. Is it the RV type or the portable one? No need to remain in the dark for long. Just pick the right one to suit your needs based on the factors outlined here.

A diesel generator: What are the pros and cons of having one?


  • It’s the least flammable fuel source. Surely that takes care of your safety concerns.
  • Unlike some of the power back up systems which are difficult to obtain, diesel generators are readily accessible.
  • Finally, you’ll appreciate that there’s on-site fuel delivery available for some consumers.


  • Short shelf life: Approximately 18–24 months
  • Installing large storage tanks ultimately raises the cost of the system
  • Diesel may not be available during power outages

Generator type: Standby or portable?

Which do you prefer? Both offer the same purpose – powering up devices and appliances in the event of a power outage. However, we believe the main difference lies in the convenience they offer. But before we start discussing which one is better, let’s quickly explain each of them so you make up your own mind:

  • Standby: This is more or less a permanent back up power supply option. Generally, this type automatically switches on when the utility power fails. Essentially that means you don’t have to be present to power it on as can be seen in the Onan 8.0HDKAK-1046 Convenient, right?
  • Portable: As the name suggests you have to physically move this type to the site where it’s needed when necessary which also means manually powering it on. Not to say the standby is better than the portable because it does come with its own advantages. For starters, it’s more ideal for those emergency situations. Secondly, its portability means you can easily move it from location to location which is handy if you need power at different sites.

guide2Now that we have a general idea of the two types, we’ll outline their key differences. From here you can decide which is best suited for your scenario:

Aside from location, one of the main differences is what these two use to function. The standby runs on natural gas and propane and it has to be hooked up to existing gas lines. The portable generator runs on gasoline. And here’s the catch: It has to be filled up every few hours. Not only that, but the oil also has to be changed frequently for optimum performance. So be prepared for that extra effort.

The second difference has to do with the design. You’ll find that a standby is fully enclosed. The opposite is true for the portable which has exposed engine parts.

Do you own sophisticated and sensitive appliances? You might want to opt for the standby which is designed to safely power a number of appliances from refrigerators to heating systems. When using a portable generator, you need to plug in your appliances to the unit via extension cables. But not just any extension will cut it. they must be rated for both the electrical appliances and distance they run to the portable generator. As a result, items that are wired to your home, such as heating and cooling systems, can’t be powered using a portable generator.

With regards to power quality, standby generators provide consistent and clean power to your sensitive electronics such as computers and TVs. Unfortunately, some portable generators – but not all – are more likely to damage or degrade these sophisticated appliances. This is because the power they deliver is of a lower quality, fluctuating often and prone to power surges.

Finally, the difference lies in the installation. Installation of standby generators requires a professional to handle the job. Needless to say, chances of him or her taking all the necessary safety precautions during installation are high. On the other hand, you’re responsible for setting up your portable generator in emergency situations. Given the fact that you’ll be operating under pressure of an unexpected power outage, you’re likely to miss some of the safety precautions. However, with a bit of time and practice, we believe you can set it up as quickly and safely as possible.

How much power do you need?

Generac01-770x472For the smaller homes, most of the household appliances are powered using anything between 3000W and 5000W. The larger home will need a 5000W to 6000W generator. Before you decide on just how much power you need, answer the following questions:

  • Will you be using city or well water? Well pumps won’t work with a generator with less than 3800W.
  • Is your heating system gas, electric, forced air or oil? With the gas or forced air system, a small generator which produces 2500W will suffice. Electric systems will need more power – up to 15 000W. In this instance, a portable generator won’t cut it.
  • Is your hot water heater electric, gas or oil fired? Gas and oil heaters require less power while the electric ones need more.

How long do you need to run your generator for?

Simply put: the purpose of a generator is to work as a back-up source of power. With that said, they’re really not designed to run continuously without rest or you risk prematurely damaging the unit.

From the reviews above you may have noticed that generators have different run times ranging from 8 hours to days.

Basically, a generator will continue to run as long as it has enough fuel. But do yourself a favor and give it some rest. Avoid leaving it to run for weeks on end.

Generator noise level

Generator noise levels are measured using the decibel (dB) rating. Here’s the general rule of thumb: For every increase in 10 decibels, expect the noise to be 10 times more powerful. Case in point: a generator which runs at 70 dB is 10 times louder than one which runs at 60 dB. This means the lower the dB the quieter it is and vice versa.

Safety features

guide1The convenience these generators offer is quite useful. However, as much as they’re welcome innovations, if not handled properly, these units can cause extensive damage.

As you might be aware, generators produce carbon monoxide which is quite deadly. It’s a good idea to have carbon monoxide and smoke detectors positioned throughout your home. You must regularly check them to ensure they’re functioning properly so your warning system is always at the ready.

Tips and tricks

For optimum performance you can incorporate the following tips with regards to installing and maintaining a generator:

  • Forget placing it in the basement. Rather position it outdoors for the reasons mentioned above.
  • Here’s a useful secret: propane is way easier to use than gas. Gasoline requires vigilance with regards to storage precautions. On the other hand, propane can be stored indefinitely plus it’s easier to refuel.
  • With regards to maintenance buy a generator that can be serviced locally. The last thing you need is trying to figure out how to transport it to the service provider each time it’s due for service.
  • Invest in a cover or enclosure – particularly for the portable generator which usually comes without – so it lasts longer.
  • We strongly advise you to power your generator every three months – for at least 30 minutes – to charge the battery. Either that or you’ll find yourself with a flat battery when it’s needed the most.
  • Always fill up your tank. When it runs out, your electronics will start sucking on the gas which can detrimental.
  • Contrary to public belief, a portable generator isn’t always the most affordable option. If anything, it requires either an expensive extension cord or a transfer switch.


The short answer is yes. Here’s why: diesel contains approximately 10% more energy by volume compared to petrol. With a diesel generator, compression basically ignites the fuel. Fuel and air are pumped into the engine separately. Since only the air is compressed, the engine is able to run more efficiently by using less fuel. In a nutshell, this simply means diesel generators use less fuel than their gasoline-powered generator counterparts. Because they are more fuel efficient, it essentially means longer run time.

Frankly speaking, the answer is yes and no.

It’s really not a deal breaker if your generator doesn’t happen to have the voltage you need. Before you go asking for a replacement generator know this: It’s very possible to alter the load of your current generator. Simply change the load. You do this by lowering the load’s resistance – be it on the AC or DC generator. Doing so will increase the current which causes the voltage to drop.

But know that this depends on the generator you have. If it’s connected to the national power grid, then it’s not possible. You can’t adjust the voltage in such instances.

The size of the generator you need will depend on a number of factors including just how many appliances you intend on powering. Obviously, more devices will require a bigger generator. But this isn’t just about the number but the type of appliances you intend on powering. Air conditioners and refrigerators draw up more wattage than lights. Other than that you need to consider how frequently you’re affected by power outages in your area. Live in hurricane prone areas? You might need the larger models so the strain of regular use won’t let it wear out too quickly. If you don’t experience as many power outages, the smaller one will suffice.

Our Verdict

Which one impresses you more? Preferences differ, but in our opinion, the best generator has to be from the Generac brand. With a power output of 50,000W, you can understand why it’s our top pick. The large 62-gallon fuel tank capacity also impressed us. It’ll be a while before it runs out of fuel. It also helps that it’s both easy to install and service.

Following close behind is the Generac XD5000E generator. This is our preferred model where portable generators are concerned. The fact that it’s very easy to transport though it’s on the heavy side is a plus. In addition, it’s easy to maintain and built to last.

Last but not least, the Onan, designed specifically for RVs, comes in at third place on our best diesel generator list. Sure, it’s on the expensive side, but we appreciate how quietly it runs. Plus, it’s also easy to maintain and above all, it’s environmentally friendly.

Do you share our sentiments, too?

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