A grouphead is considered to be the parts on the machine whereby the espresso is extracted. Each grouphead, typically, can produce a single or double espresso extraction. The most common machiens have one and two groupheads. Busy facilities will have a machine with three or four groupheads. Except for compact machines, the boiler size usually increases with the number of groupheads.
When deciding on an espresso machine, it is important to first determine the maximum projected production required; second, any space limitations; third, select on design of the machine to fit the front of house ambiance; fourth, price.
Commercial machines with a double boiler typically have higher repair costs due to the fact that additional components are present and sometimes time is spent removing good components to get to the components that need to be replaced.