Re: generators
Sorry Snowbird, let me see if I can keep my head out of the clouds.
A RV has 2 (for 30 Amp) or 3 (for 50 amp) wires going into it. The power used in the RV, in watts, is defined as the current going through the wires into the RV times the voltage across the wires into the RV. In math terms, Power = Current * Voltage.
So, let's take a 30 Amp RV. The maximum current which can go into the RV is 30 Amps. Let's call the 'normal' voltage across the 2 wires as 120 Volts. Thus the power consumed by the RV is a maximum of 120 volts * 30 amps = 3600 watts. This is sometimes abbreviated as 3.6 Kilowatts or 3.6 KW.
With me so far? If not, let me know what I'm not explaining clearly enough.
Now, if a generator is 'rated' to be 4.0 KW, it is very likely that is the PEAK or HIGHEST power it can provide. Generally the generator manufacturer 'limits' you to that value for say 10% of the time the generator is running. The rest of the time you must use a lower amount of power often called the 'duty' rating. For a 4KW generator, this is around 3700 watts, plus or minus depending on the manufacturer.
Thus a 4KW generator (or 2 2KW generators hooked together, which mostly only Honda can do) will easily handle a 30 Amp trailer. You can run a 30 Amp trailer on 3000 watts of generator; I have done it and so has GTS and probably many others. It just means that the breaker on the generator will pop before the breaker in the RV.
Now for the advanced course, the 50 Amp RV
This RV has 2 wires going in, and 1 wire coming out. So 50 amps can go in 1 wire and 50 amps can go in the other wire, and the voltage from each of these wires to the 3rd wire is 120 volts. So the power used could be as high as (50 amps * 120 volts) + 50 amps * 120 volts) = 12,000 watts or 12KW. This is how much power the outlet will supply without popping the breaker and how much power the RV can accept without popping its breaker.
Fortunately, very few RVs can actually USE 12KW (have that much electrical stuff in them). Which is why most 50 Amp RVs only have 6KW to 8KW generators in them.
Whew, any questions?
If you understand this and are interested, I can attempt to explain why you can have only 1 wire coming out of a 50 Amp RV when there are 2 wires going in...