The very first espresso machines worked on a steam-pressure basis, and they’re still in use today. With this type of machine, steam or steam pressure is used to force water through the coffee grounds and produce espresso. Some steam-driven machines can produce a measure of foam “crema.” But they can’t generate enough pressure or provide the precise temperature control necessary to produce true espresso: They simply make a very strong cup of coffee. However, they cost considerably less than pump-driven machines. Our verdict is that if you’re a true espresso lover and seeking to make a good shot at home, we recommend you steer clear of steam-driven machines. They’ll likely disappoint you.
In the semi-automatic machine, water pressure and temperature must be stable and consistent, and according to our expert, the pressure shouldn't be too high. Typically, coffee is brewed at a pressure of about 10 bars, and an ideal water temperature is around 195 degrees. Generally, the more expensive the machine, the better the equipment inside that regulates these two factors. High-quality machines tend to have a mechanism called a PID, or proportional-integral-derivative, controller. The PID's function is to maintain constant water temperature with extreme accuracy, down to the degree. Two central problems plaguing inexpensive espresso machines is that they lack a PID, meaning the temperature of the brewing water can fluctuate up and down and yield inconsistent results. Inexpensive machines often advertise that they have 15 or 20 bars of pressure as a selling point. But, higher pressure is not the priority, and too much pressure can actually lead to over-extraction and bitterness in your espresso shot. Therefore, we looked for a machine with good temperature and pressure control.
For many of us, the daily grind can't begin until we've had that first cup of piping hot coffee—so the right brewer is at the top of the list. The most basic coffee makers make at least a decent cup, but a little more money buys conveniences such as programmability, a thermal carafe to keep coffee hot longer, settings that let you adjust brew strength, and more.