When shopping for an espresso machine, among the millions of features advertised is the bar pressure rating of the machine, meaning how much pressure is used to force the water through the coffee grounds in the portafilter.
Bars are a measurement of atmospheric pressure, so one bar of pressure is equal to the amount of natural pressure at sea level, meaning 10 bars is 10 times the amount of pressure at sea level.
With the industry standard set at 9 bars, do people really need over 15 bars of pressure to brew high quality espresso?
The short answer is that no, anything over 10 bars won’t really increase the quality of espresso. Though, machines that are able to push out a higher amount of pressure can, in some cases, help the user brew better espresso than that of a machine only able to push 9 bars.
It is fair to assume that many machines advertising a higher bar pressure only produce a low amount of bar when the machine is actually in use. Cheaper machines will also deteriorate more quickly and the bar pressure will drop over time as components wear out.
It is more important to be competent with a 9 bar espresso machine than to not use a 15 bar machine properly. The idea of adding more bars of pressure to espresso machines somewhat hales from the “bigger is better” mentality, tricking consumers into paying more for something that’s not necessarily needed.
For the most part, 7-9 bars of pressure is considered the sweet spot for pump driven espresso machines, which use a pump to force water through the grounds. Pump driven machines, as well as rotary ones, are known to be much better than those that brew using steam, known as steam driven.
An example of a steam driven espresso machine would be the kind sitting on store shelves that seem to cost an unusually low amount when compared to other espresso machines.
These machines use a broiler inside that heats water, and in turn builds steam pressure, which is pushed through the bed of coffee grounds by use of its own force. With the optimal brewing temperature being 200 degrees Fahrenheit (93.3 degrees Celsius), and the point at which water turn being hotter than that, the resulting coffee will taste burnt and over-extracted.
Steaming milk with these machines can also be a bit of a gamble. Not because the steam wand is lacking power, but because the transition from espresso to steaming milk, or vise versa, can take quite a while.
With a pump or rotary driven espresso machine, this is not the case. The water inside is heated with either a broiler, or heat exchanger, to the optimal temperature. Once that temperature is reached, it is pumped through with great force with the rotary motor or pump, pulling perfect espresso shots in the process.
Overall, pump espresso machines, as well as rotary ones, are able to brew much better espresso than steam driven ones, and perfect espresso can be brewed with as little as 8 bars of pressure.