Genset 3.0 sort of indicates it's an Onan brand? More details would help us help you figure it out, like brand and model number beyond 3.0. If you look on the generator, there are usually circuit breakers marked with in amps. Assuming it generates 120 volts, multiply 120 times the amps of the circuit breaker and that will tell you how many watts it generates. Again, Watts = Volts x Amps.
Bob & Donna
'98 Gulf Stream Sun Voyager DP being pushed by a '00 Beetle TDI