A baby cow is called a calf. Adult male cows are called bulls. Adult female cows are called heifers until they give birth; after they have given birth, they are called cows.
As long as there is a fuel supply of natural gas or propane, a well-maintained backup generator will keep running. If the Generac generator is running on propane, with a 500-gallon tank, it should run 24 hours a day for over a week. How loud are they? Generac generators are very quiet.
A conventional generator is nothing more than an engine connected to an alternator and run at a speed that produces the desired AC frequency, regardless of the load on it (as the load increases the engine throttles up to keep the engine speed the same).