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How Good Are Onan RV Generators?

How Good Are Onan RV Generators?

Many campers enjoy RVing for its many comforts, such as air conditioning, microwaves, and television. Although numerous campgrounds offer electrical hookups, you may not always have access to electricity everywhere you go. That’s when a built-in Onan RV generator in your storage bay comes in handy. However, is it worth installing one of these or are there better options.

What Is an Onan RV Generator?

Made by Cummins Inc., Onan generators are portable engine-driven power stations for your RV. An Onan RV generator is a dependable engine that can power your coach.

New to RV Generators? Start here with our Complete Guide To RV Generators.

built in cummins generator

You can get Onan generators that run on gasoline, diesel, or liquid propane. Most regular recreation vehicles have gasoline or propane power sources. Larger heavy road vehicles, farm machinery, busses, and large coaches use diesel generators.

Most Onan generators are permanently built into RVs and come in various sizes to power small, medium, and large rigs. From the tiny QG 2800i to the full split-phase QD 12500 and now even a portable unit Onan has a generator to meet the needs of any sized motorized camper. 

Pro Tip: Find out What Size Generator You Need For Your RV?

cummins onan portable generator
The portable line is the latest in Cummins Onan generators, however, these are not actually made by Cummins but outsourced.

Onan RV Generator Overview

David Onan built the first Onan generator in 1926 at a friend’s request. It has evolved over the years to today’s units like the MicroQuiet 4000. Onan RV generators mount permanently in many motorhomes. They’re lightweight compared to older counterparts, quieter, easier to install and use less fuel. 

In general, Onan power systems are lightweight and were built with more oil capacity. This leads to fewer problems and longer intervals between maintenance. The lighter weights also means RVers can pack more.

Onan has more than 85% of the market share in the RV generator business. They provide a high-quality product that does exactly what it claims — provide power for recreational vehicles of various shapes and sizes and last for years. 

Cummins quiet diesel
This is the top of the line Cummins Quiet Diesel generator

Benefits of an Onan RV Generator

Onan is renowned for its dependability. If you purchase an RV with one of these generators in it, chances are the generator will outlast the recreational vehicle if maintained properly.

Most RVers want a ready power source that stays out of the way. They start with the flick of a switch, are much quieter than in past years, and save a considerable amount of fuel. Having a built-in generator, it can be started remotely and can quickly recharge batteries.

Some of Onan’s more recent additions have electronic ignition or Permanent Magnet Alternators (PMA), which use the rotor’s magnetic field to generate power. This makes the generator quieter with fewer vibrations and lowers fuel consumption because it can slow down the engine. 

Drawbacks of an Onan RV Generator

Having a built-in generator means that if it needs to be maintained it will need to be done at the RV. This can be a drawback from a portable unit that can be fixed anywhere.

Being built in also means that it will always be in the same spot and same noise level. A portable unit can be moved away from the RV so that its quieter for the owners.

built in RV generator exhaust

The cost of these generators is also a drawback. Onan RV power stations ranging in size from 2500 to 5500 watts can run from $3,100 to $4,600. Many recreational vehicles come with one already installed, but if you are considering adding a generator to an existing rig, the price is a little steep.

These generators also tend to be a bit noisy. Remember to be considerate and obey quiet hours to avoid annoying your neighbors.

While properly maintained these tend to be great generators, but let them sit and problems can arise.

Common Problems with Cummins Onan Generators

As with any engine, storage can be a major problem. Carburetor issues from sitting for months without use are the most common. The intake valve can become varnished, requiring a little coddling before it may start.

Even then it may not run well and need a rebuild. Ideally to prevent this utilizing fuel stabilizers and draining fuel from the carburetors before storing can eliminate most of these issues.

generator maintenance

Choosing a propane-powered engine can also eliminate the storage issues as the fuel does not go bad.

Another common problem we have seen with Cummins Onan generators is burning oil. Many of them have a low oil shutoff that will prevent the engine from running or shut it down when it gets hot. Keeping tabs on oil use is important.

Our Favorite Features

With only 15% of the RV crowd using another generator brand, there must be several features that make Onan so popular. Here are our top four reasons to own an Onan RV generator.

Quiet with Low Vibrations

In general Onan generators operate relatively quietly with a low tone sound. They also utilize metal springs or rubber to dampen motor vibrations.

Onan also has designed an inverter generator that works at variable speeds with newer permanent magnet alternators, emitting less noise and fewer vibrations. You’ll no longer feel that ‘shimmy’ inside your RV when the generator runs, and your neighbors might not even know it’s on!

cummins inverter generator
Models with an “I” at the end signify inverter. Source:

Low Fuel Consumption

You usually have to watch your power station’s existing fuel tanks. Most generators automatically turn off when it hits a quarter tank in a motorhome. However, Onan’s newer offerings run through fuel slower, giving you more electricity and more mileage, saving you money and worry.

Widely Available Parts

Because these generators are so common getting parts or maintenance is pretty easy. Many of their offerings have some standardization and parts can be swapped.

Reliable (when properly maintained)

Yes, we have had trouble with Cummins Onan generators in our RVs before, but it was almost always due to a fuel issue due to sitting. Our 22-year-old propane Onan still starts easily and has had nothing but oil changes. Always properly maintain and properly store the engine and it should last a long time.

old cummins generator
Despite being 22 years old our little Onan still fires right up!

Are Onan RV Generators Worth the Cost?

If you’re boondocking in the middle of the desert in August, having a generator to run your air conditioner is likely worth the cost. But if you enjoy staying at full hookup campsites, you may think twice about spending a lot of cash on a ‘backup’ power plan. 

Having a backup power plan can be easily and cheaply accomplished with a portable generator. However, if the convenience of pushing a button to have power is worth it then an Onan is a good choice. It gives you power when you need it and peace of mind when you don’t.

A Versatile Energy Source

In some areas, brown-outs and sky-high utility bills have made powering a traditional home less dependable and more expensive. But your recreational vehicle probably already has a power solution built into its infrastructure. 

The Onan RV generator can become your only energy source when camping off-grid or in an emergency. Its dependability and consistent energy production give every camping trip a sense of satisfaction, knowing you can go anywhere without forfeiting comfort and amenities.

Does your RV have an Onan generator? Let us know how you like it in the comments below!

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They left their jobs, sold their house and possessions, and hit the road in September 2015 in their full-time “home on wheels”. Since then they have traveled the US, Canada, and even internationally by RV.
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Joseph Snyder

Sunday 23rd of July 2023

I’ve had nothing but trouble with Onan. And their OEM parts prices are through the roof. If you don’t constantly baby your Onan generator it will not run properly. Sometimes I wonder why they are the most common RV generator. With heat apparently being a huge issue with them on RVs, why are they always stuffed in some tiny tight compartment where heat builds up like crazy? I’m switching to Honda or even the Predator from Harbor Freight and carrying a separate fuel container in a rear cargo carrier. Onan isn’t worth the headache. I want to use my generator and have some power and AC in the summer. I don’t want to constantly sit on the ground next to my RV “maintaining” my overly sensitive generator.

Mortons on the Move

Wednesday 2nd of August 2023

Thanks for your thoughts, I personally have seen better reliability with both Hondas and predators. I think RV manufacturers frequently poorly install them however as well which causes heat problems. Our 10kw diesel onan has been great but it has a huge liquid cooling system and is setup properly. It also has a Kubota engine in it tho which is kinda weird lol.

Remi DeLouche

Monday 26th of July 2021

I have owned multiple brands of generators, most inverter, for tailgateing and as backup for our business employees and customers. This because we live in a College Town And our Gulf Coast location make us vunerable to hurricanes. My purchase of my RV with a 5500 Onan carb model is by far the most durable and reliable model of all we have owned, so much so I set it up so it could power my home is needed in a power outage. Watching it easily carry a heavy load I have come to believe the "5500" is not the typical MAX that the generator can output but the sustainable capability of the Onan generator. That displays the type of design and confidence that Onan has in its products....

Mortons on the Move

Thursday 29th of July 2021

Thanks for sharing your experience!

Tom Macklin

Saturday 24th of July 2021

I have a gas 5500 watt unit in my 5th wheel toyhauler. It starts and runs fine. I would caution anyone who performs their own maintenance to use original Onan parts. You can buy cheaper parts, but that's exactly what they are. Your unit will thank you for it by performing as it was intended too.

Mortons on the Move

Sunday 25th of July 2021

Thanks for sharing!


Saturday 24th of July 2021

We ran (just sold our rig) an Onan 6000 QD on our DP that was extremely quiet in most conditions. Very fuel efficient and worked great for the six years we owned the rig. We exercised it monthly and changed the oil, etc. to manufacturers specs. Only issue is at altitude. Around 10,000 ft. and up, the unit ran extremely rough and would smoke out of the exhaust until it warmed up. Once we exited the mountains the unit was back to normal. Great unit though.

Mortons on the Move

Sunday 25th of July 2021

Glad to hear you liked your Onan overall. :)

Mark Eckman

Friday 23rd of July 2021

Our Onan 5500 works well in our Newmar Baystar and is very convenient. I do monitor the gas usage and find if it is running while driving it reduced our MPGs by about 1.9 and if we are using it for boondocking, about 1.8g/hr. So we consider the cost of generator use when we stop at a Walmart or Cracker Barrel. On nights with extreme temperatures, it can be expensive compared to nearby campgrounds.

Mortons on the Move

Thursday 29th of July 2021

Good point, sometimes you do have to weigh the cost of the gas used by the generator.