Yikes! Combustion from propane fueled engines may be cleaner than gasoline or diesel, but they still produce carbon monoxide and definitely should not ever be used indoors!
I'm sure you meant something else. Whew!
In my business, I use generators all the time, from 6KW & 9KW propane generators to 35 KW diesels. 24 hours of operation under 80% load with either the 6KW or 9KW propane unit, you can expect to use nearly all of a 100 lb tank of propane. There's more energy in the same amount of gasoline, therefore you'll burn less per hour for the same amount of kw used. Most RV's do not carry enough propane to provide you a continuous 24 hours of full load operation. Then what, detach your tanks or worse break down camp everyday to find the nearest propane station? Up to you.
The true benefit of propane or natural gas generators vs. gasoline or diesel ones would be for emergency standby generator attached to your home or business. Since the propane and natural gas can be stored indefinitely without degrading like gasoline or diesel can, it makes an ideal fuel choice for emergency generators. Additionally, in most natural disasters [like Hurricane Katrina, etc], most natural gas lines were still online,and propane was more readily available than gasoline or diesel. This was from my general overall experience with Hurricanes Andrew,Hugo, Charley, Francis, Jeane, Ivan, Katrina, Rita, Wilma and Ike.
So being forced to pick a fuel for or RV boondocker generator. I'd stick with gasoline [they are the least expensive], unless you already have a diesel powered rig that you can tap into.
Hope that helps
There are a few different reasons for using one or the other fuel for a generator. In the RV world you choose the fuel you have the most of as a general rule.
SO if it's a Class A with a motor and a big fuel tank to propell it down the road.. You use that fuel. Gas or Diesel, Why, cause I carry up to 70 gallons of it, that's why, I only carry about 25 of Propane.
If it's a trailer, you don't have a gasoline or diesel tank.. but you do have Propane tanks So.. There you go.
Other considerations is proapne burns cleaner, mostly water out the exhaust, so you can use it indoors.
Propane also has a much, much, much, much, longer "Shelf Life" (Gas anythign over about three months you need to worry and six you shoudl toss it, Diesel.. I'm not sure but I've seen some very nasty diesel fuel too. Propane basically never goes bad making it the ideal "Standby" fuel)
But for RV use you use the fuel you have the most of. Your main engine fuel if it's a motor home.