Motorhome Generator: Diesel vs. Propane

Motorhome Generators - Diesel vs Propane

When buying motorhome, you may be faced with the decision on what kind of RV onboard generator will you want; diesel or propane. After seven years on the road in three different RVs, we now feel comfortable discussing the differences between the two in motorhomes. As well, we’ll share the pros and cons between diesel versus propane generators.

Motorhome Generators

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MOTORHOME ONBOARD GENERATOR: DIESEL vs. PROPANE

DIESEL POWERED ONBOARD GENERATOR

PROS of Diesel Generators

    • Computer-controlled constant speed operation – quiet diesel performance for smaller RVs
    • Special sound-controlling housing encloses cooling system and muffler
    • Double isolation mounting system reduces vibration
    • Easy, accessible maintenance points
    • Runs one rooftop air conditioner with power to spare
    • Integrated start/stop control with hour meter
    • Intended for OEM (Original Equipment Manufacturer) use only

Cummins Onan Diesel Generator

Availability of Diesel Fuel

A major concern when choosing an RV generator is availability of fuel. During our travels, we find diesel fuel is more readily available than propane. There’s no hassle trying to find fuel anywhere. We also enjoy the fact that our generator is fueled from our diesel fuel tank in our motorhome. This means we can power two engines from a single fuel tank.

Fuel Efficiency

A diesel generator is more efficient and economical than an onboard propane generator. Our Cummins Onan diesel generator uses about one third of a gallon of fuel per hour operating under a full load of electricity. We can power our motorhome for about 60 hours before we need to refuel. This is a huge benefit when boondocking.

By the way, our motorhome has a built in safety feature that shuts our RV generator off before the coaches fuel tank is empty. This allows us to still drive  our motorhome to a fuel station with proper planning.

Dependability

In our opinion, we find our diesel generator to be very dependable. And generator maintenance is easy to do and cost effective. If outside maintenance is necessary, any diesel mechanic should be able to assist in regular service, troubleshooting and repairs.

CONS of Diesel Generators

Initial Cost

Perhaps the largest drawback to an RV onboard diesel generator is the initial cost. A diesel generator will cost upwards to twice that of a onboard propane generator. That said, you’ll need to consider how you will use your RV to determine if you should shoulder this initial cost.

On a positive note, you will recoup that money when you sell the RV if the onboard generator is fully-operative.

Fuel Cost

Of course, fuel cost is a fluctuating factor. And it also depends on geographical location. As we know, certain regions of the country experience higher fuel costs. And the economy plays hugely into RV generator operating expense as well. Obviously, when diesel prices are low, it will take less to operate an onboard diesel generator.

So really, fuel cost can swing from being a pro to a con and back again depending on the economy. This consideration is ever changing, but one for you to think about.

For example, the date of publication of this blog, for $36 we can power every aspect of our motorhome for 2 and 1/2 days.

Slightly Less Power

Our Class C motorhome’s pre-installed onboard Cummins Onan 3200QD RV generator is rated to produce 3200 watts under ideal conditions. This is less than its sister propane-powered generator that produces a higher 3600 watts. Personally we find this difference to be negligible, but is still less power.

We still can power all of the appliances in our motorhome all the time. However, we are mindful of not overloading our electric output which puts strain on any generator.

Fumes and Noise

Sound and fumes from diesel generators are argumentative. In fact, that very subject is discussed frequently on social media and around the campfire. It is true, diesel generators do emit an exhaust odor and fumes. However, those exhaust fumes can be overcome by installing a Gen-turi exhaust venting system (specifications of Gen-turi in link) to vent the exhaust above the roofline of your motorhome.

Motorhome Generators - Gen-turi

Many campers also find diesel generators to be louder than their propane-powered counterparts. This really depends on several factors. Mainly, it’s where the generator is located in the RV, where the RV is parked when running the generator and location of windows and door in conjunction to the RV diesel generator exhaust pipe.

In our case, we rarely if not, use our onboard diesel generator except for routine maintenance. We invested in a great solar and energy management system installed (by us) in our Class C Winnebago View motorhome,

BLOGGER’S NOTE: In Class A motorhomes, the diesel generator is located in the front of the motorhome. However, in Class C motorhomes, the diesel generator is located in the back.

PROPANE-POWERED ONBOARD GENERATOR

PROS of Propane Generators

    • Cummins Onan LP Onboard Generator
    • Meets National Park Service sound level requirements (60 dB(A) @ 50 ft.)
    • USDA Forest Service-approved, spark-arresting muffler.
    • Microprocessor control with diagnostics and troubleshooting.
    • 4-point vibration isolation for exceptionally smooth, quiet operation.
    • Cummins-Onan OHV engine for Fuel Efficient Operation
    • Lightweight, compact design includes full housing with enclosed muffler.
    • 3-Year Consumer Warranty.
Cummins Onan QG 3600 LP generator

Initial Purchase Cost

The most obvious point to consider is the money you save by purchasing an RV with an pre-installed propane powered generator. In fact, it could cost you thousands of dollars less if you buy a propane generator.

But of course, you will need to assess how the motorhome’s generator will be used. You could possible roll those savings into installing more efficient RV batteries, solar panels and components needed for a reliable energy management system for your motorhome.

If you are a park-to-park camper plugging into an electric pedestal every night, then it’s wise to purchase an RV equipped with a propane generator.

Burns Cleaner

Onboard propane generators burn cleaner and don’t have the exhaust odors associated with diesel generators. Which means you won’t annoy your neighbors with the exhaust. And of course, you will not have to install or use a Genturi.

Slightly More Power – 400 watts more

It is a fact that a motorhome’s propane generator produces 400 more watts than its diesel counterpart. This may come in handy if more power is needed while using multiple appliances or air conditioners.

Also, onboard propane generators weigh significantly less. Just something you should consider if your motorhome is weight critical. Less weight is very appealing to RV buyers as is the initial cost.

Quieter?

As we mentioned as a con of diesel generators, the debate of propane generators being quieter than diesel is ongoing. Many motorhome owners claim that propane generators are quieter. Personally, we cannot take a side one way or the other as we personally can’t really tell the a difference. Besides, we rarely use our generator except for multiple cloudy days to recharge our batteries when boondocking.

CONS of Propane Generators

Propane availability and Efficiency

The first point to consider when deciding which type of generator is best for you is availability of fuel. Propane can be more of a challenge to find is some regions of the country. Adding in, location of some propane refilling stations aren’t conducive to getting your big rig motorhome to access them.

The second concern is the inefficiency of propane generators. An onboard propane generator operating under a full load can easily burn through 10 gallons of propane in 24 hours. This could cost about $25-$30 per day. That’s twice as much as a diesel-powered generator.

Also be aware, a propane generator can consume every bit of propane in your motorhome’s propane tank. It will not shut itself before emptying your propane tank, thus leaving your heat, water heater and gas cooking appliances unavailable.

BLOGGER’S NOTE: In Class C motorhomes, propane generators are always located aft of the motorhome.

Cummins Onan Diesel Generator

It comes down to this…

We hope our dissection and differentials between motorhome onboard diesel and propane generators helps give perspective of what to expect. Generator preference really comes down to much money you want to spend and how you are going to use your RV.

If you are a boondocker or need to run your generator for hours at a time, you may want to lean more towards the diesel option. The initial upfront cost will be offset by accessibility to fuel and fuel cost per usage.

If you’re a park-to-park camper plugged in most of the time, you probably are better off choosing the propane option. The thousands of dollars you save can be better spent on campsites or invest in better batteries or solar panels.

Motorhome Generators - Maintenance Oil Change

Whatever you decide, be aware that regular periodic maintenance is the key to successful generator life and operation. Too often, generators are ignored until they are needed and won’t start or run properly. Also, it’s imperative to exercise an RV generator every month for at least two hours under load to keep it fully operative and reliable.

And lastly, these later model Cummins Onan onboard generators are quieter than National Park Service sound level requirements. They are intended for Original Equipment Manufacturer use in RV applications only.

A side note, if buying a pre-owned RV that has low hour usage on the generator, be weary that it may not have been properly serviced or maintained.

Motorhome Generators-2

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