Copyright 2019 Discovery Owner's Association, Inc.

Diesel vs. LP Generator

On most motorhomes, as on the Discovery, you can choose between a diesel or LP generator. Here are some things to consider to help you decide.

Yes, the diesel generator does add substantial cost compared to the standard LP generator. However, you also get two additional 6 volt deep cycle batteries and a 2000 watt inverter instead of a 1000 watt inverter. If you are the least bit handy, you can add the two extra batteries yourself, at a cost of around $120 if you get them at Sam's Club. The bigger inverter is nice, primarily because it has a 100 amp charger instead of a 50 amp charger on the 1000 watt inverter. Other than the bigger charger, for most people the bigger inverter is of small value as the 1000 watt inverter is capable of operating the microwave for short periods of time, adequate to heat leftovers or a cup of coffee. The diesel generator also adds considerable weight compared to the LP generator. This may be a major consideration on some motorhomes, but is usually not a problem with the D with its great carrying capacity on its front axle. Also, note that you will recover some of your initial outlay at resale time.

I hate to "hunt" for propane and take the time to fill the LP tank(s). On the other hand, I always have to fill up with diesel anyways, and sometimes I think it would be really nice to have a diesel generator. The diesel generator would be a great benefit if you use your roof air conditioners to cool the coach while on the road. My wife and I are almost always the only one if our D and we have not travelled in areas where we had to use the roof air to cool the coach, so this may or may not be a consideration for you. We have used the generator to run the roof air when we were boondocking in hot and humid weather and found that we can run both air conditioners for about 44 hours on one tank of LP.

As far as using the LP generator to charge the house batteries, it takes a L O N G time with the 50 amp charger in the standard 1000 watt inverter. While doing extensive boondocking in Alaska, I found it much more economical and quicker to just idle the D's ISB engine to charge the house batteries as I did not have a need for any air conditioning.

I had heard from a fellow D owner with a diesel generator that the Onan-mandated 500 hour maintenance cost $500. Needless to say, this had me really concerned! So, the next time I was at an Onan service facility I had to ask for myself. I was told by their service manager that the 500 hour diesel generator maintenance could cost $500 for all the maintenance items. Note that this adds $1/hour to the cost of running the diesel generator. I then asked what the 500 hour maintenance would cost for my LP generator and was told about $85, primarily because the LP generator burns a lot cleaner. I only asked one Onan dealer about this. I strongly urge that you verify this with your local Onan dealer.

With the recent wild swings in fuel costs, sometimes the LP and sometimes the diesel would be cheaper to run. We have paid anywheres from 90 cents to $2 per gallon for LP and from $1 to $1.50 for diesel. Under most load conditions, the diesel is slightly more fuel-efficient. This will probably not be a prime consideration since most of us do not put a lot of hours on our generators.

As noted earlier, you will recoup some of the initial cost at resale. Some folks will only consider a diesel generator, especially on a luxury motorhome.

The diesel generator is also quieter and can meet noise requirements for use in some parks. The diesel generator certainly has panache over the LP generator, if that is important to you.

In 1998, there wasn't an option for the diesel generator. This was something I really wanted, along with the extra batteries and 2000 watt inverter. However, being the cheapskate that I am, I would have not have chosen this option had it been available - especially after having lived with the LP generator full-time for since 1998.

I welcome your comments. Send them to me and I will post.

- Submitted by Bob Cook


The DISCOVERY OWNERS ASSOCIATION, INC, was formed to promote the sharing of information and the camaraderie of fellow Discovery motorhome owners. Membership in the club is limited to owners of Fleetwood Discovery motorhomes.


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