For our customers that want the ability to pull consistent, traditional cafe-grade espresso back to back (all day if necessary), we highly recommend considering La Spaziale's S2 commercial machines. Available in one, two and three groups, the EK model offers volumetric shot programming (as well as the option to manually control shots) and is available in 110v or 220v at no added charge.
The S2 has been designed for the rigorous demand of the Italian market, so in American cafe or office use it won't even break a sweat. The reason for this machine's tremendous capacity and consistency lies in its patented steam-heat exchanger system. In contrast to dual boiler espresso machines (which have a finite shot capacity before they need to reheat), the huge volume of steam from the S2's three liter boiler (for one group, five liter for two group) heats the brewing water as it passes from the water line to the group head. This improves efficiency (because the machine doesn't need to reheat as often), improves brew temperature consistency (because the brewing water isn't draining the boiler), and less opportunity for scale buildup than traditional heat exchangers (which rely on water circulation).
The S2 machine is tuned to pull shots consistently at 200 degrees, which is perfect for most coffees. For very light or dark roasts, you may prefer to have the added temperature control of a dual boiler. But for customers that don't want to change brewing temperature, a heat exchanger will produce a more temperature stable shot than a dual boiler at about half the price. Another advantage of heat exchangers is their mechanical simplicity means maintenance is more affordable and less frequently needed. Many of our customers choose to improve their espresso by saving money on their machine to invest in a top-of-the-line grinder, as this makes a more noticeable difference in the flavor.