We've all seen it. We've all heard it. We've all been next to 'that guy.' The big loud, smelly generator that they bought for Y2K. While they put out a good amount of power, you will pay with your hearing.
Five years ago, I bought a Honda EU2000i generator. Not only are they quiet, they are very fuel efficient. We've gone up to 8 hours on 1 tank (~1 gallon) of gas.
You can join two of these generators together to get even more power.
The Honda also has an "ECO" mode, where it will run at lower RPMs until the load increases. Even at the higher RPM, it is still very quiet.
The first time I've come across one of these generators, I stood there like an idiot wondering if it was even on, because there was a noise maker generator across the aisle in the lot.
The problem with these generators is the price. While they are spendy, as they say: "Buy once, Cry once." It is money well spent for a great setup.