Commercial espresso machines are normally NSF & UL approved for the US market. The machines come in two main categories, traditional and super automatics.
They are then divided between heat exchanger and multi boiler in both traditional and super automatics. and then one or two step Super Automatic.
Heat exchanger machines normally have 1 point of temperature reference for controlling the steam and espresso water temperature via a pressure stat in the boiler normally providing a 3 to 2 degree swing up & down in temperature. Some machines do have the ability to have cold water and hot water mixed at the brew group for modifying the brew water temperature to a limited degree. The average food service 2 group has a 3,500 watts of power generally used in food service operation where hot beverage is served in 6 to 8 oz. cups and were water temperature is not a critical factor to serving consistent espresso. The next level of power is around 4,500 watts, they are better suited for to go cup service of 12 to 16oz.in a café or small coffee house. There are heat exchanger machines that have a more sensitive pressure stat of 2 degree swing up or down or PID thermostat for improved temperature control and offer higher power rating to help maintain improved water temperature stability for busy up scale busy restaurants or coffee shops.
Independent boiler machines with a PID temperature control are normally used where cappuccino is served in larger to go cups of 12 to 22 oz. and espresso water temperature is a critical factor in achieving a more consistent tasting espresso coffee or when using 2 different coffees that may require different temperatures for getting the best taste from the coffee. the water temperature is controlled through a PID temperature controlled thermostat with a 1 to 1/2 degree temperature control.