Basically it depends on your need if you want to use some high voltage appliance then 3600 watt or above power are enough otherwise 1,500 to 2,000 watt generator are the best option for a 30 amp You can use the maximum size of the generator 3,600 watts for a 30 amp, this will be good enough for an RV and for a house if you plan to use some high voltage devices. various types of brands offer that power on 30 amp with portable generators including dual or single fuel consumption brands like be Honda, Craftsman and more. As per new innovation on HVAC companies also improve noise and make them more quiet as possible. if you use 3,600 watt generator or above that require some power management in especially when your are running high powered electronics appliance such as hair dryers, air conditioners and heaters; you can use that thing as making schedule. because if you use on single time high power appliances can cause overload because the high consumption capacity of high load appliance are 15 or 20 amp if the use on single time  trip the circuit or may cause any other. If your program ignores high powered electric products then you need a smaller generator. 2000 watt generators are good enough for RVs. That type of generator not only produces low power as well as provides other capabilities such as small size make it portable, small engine produce low noise that make it quieter and you can carry it anywhere.