This factor depends on your RV design. You have to match it with the motor of the RV. For example, if you own a diesel-powered RV, then you should purchase a diesel generator. But most of the travel RV used propane units. But if you have a big RV and big groups to operate, then the diesel generator would be best. The other best option is Gasoline. It can be readily available, and it is less costly. Moreover, the propane unit is the best option to keep safe in the environment. But it has one drawback that is its fuel tank is limited.