The bar number on an espresso machine is the pump's rating, not the pressure at the coffee, and the manufacturers say so themselves. Breville's page for the Bambino describes a low pressure pre-infusion followed by a 131 psi (9 bar) extraction delivered by what the page calls a 15 bar Italian pump, which is 218 psi of pump against 131 psi at the puck. A 20-bar badge describes the same component one step further from the cup. The condition that changes which figure matters is the grinder: pressure at the puck is produced by resistance, and resistance comes from the grind, so a machine's pump rating tells you nothing until the grind is set.
A pump rating is not brew pressure
Nine bar is the number the drink is built around, and the 15 or 20 bar figure on a box is the pump's maximum capability with no coffee in the way. Breville prints both on the same page, along with the two figures that decide the dose: a 54 mm portafilter (2.1 inches) and 18 grams (0.6 ounce) of ground coffee. Those are the numbers that make baskets and tampers compatible or not.
The Istituto Espresso Italiano, which runs the Espresso Italiano Certificato scheme, defines the result rather than the machine: its page on the certified espresso describes a cup containing approximately 0.8 fluid ounce (25 milliliters) of coffee, the product of a three-year study, and certifies bars against that definition. A machine specification that cannot be connected to a cup volume and a dose is not a specification about coffee.
The boiler decides temperature, and it is small
A single-boiler machine has to heat brew water and steam milk from the same vessel, and the vessel is smaller than most people expect. Rancilio's technical specifications for the Silvia list a 10.1-fluid-ounce (0.3-liter) coffee boiler, a brass brewing group, a vibration pump, a thermostat for temperature regulation, no pressure gauge on the coffee boiler, a 2-liter water tank, and a power supply of 950 to 1,000 watts at 120 volts. The portafilter holds filters to 21 grams, with filter baskets of 8 and 16 grams and of 14 and 18 grams.
Example, on Rancilio's published figures: 950 to 1,000 watts at 120 volts is 7.9 to 8.3 amps. The 10.1-fluid-ounce boiler holds twelve times the Istituto's 0.8-fluid-ounce cup, so the boiler is not sized for capacity; it is sized to hold a temperature. Regulation by thermostat means the element switches around a set point rather than holding one, and the sheet's "no pressure gauge on the coffee boiler" is the reason the brew pressure is not something the owner reads. Both facts belong to the same design choice, and both are printed by the manufacturer.
Heating system, not heating adjectives
Breville states that its ThermoJet system reaches extraction temperature in 3 seconds and, on the same page, that the machine uses up to 32 percent less energy annually than a thermoblock system, attributed to internal benchmark testing as of November 2022. That is a manufacturer's own bench comparison with a named date, which is how such a figure should be read: it is evidence about two of the manufacturer's own designs, not a category result.
Between a thermoblock, a single boiler and a dual boiler, the specification that separates them is what the machine can do at the same time. A single boiler switches between brewing and steaming; a dual boiler does not. Neither sheet needs an adjective to say so. The figure that shows which design is in the box is the boiler capacity: Rancilio prints 10.1 fluid ounces for the Silvia, and a machine that prints no boiler capacity at all is usually heating water in a block as it passes through. Ask for the number rather than for the name of the technology.
What the machine costs after the box
Espresso has consumables the way a countertop fryer has a basket: group gaskets, shower screens, filter baskets, water filters and descaler. The parts to price before the machine are the ones tied to its dimensions, and the portafilter diameter fixes most of them, which is why Breville's 54 mm and the commercial 58 mm are separate accessory markets.
The grinder is the larger number. A machine bought without one cannot reach the 9 bar its own page describes, because the puck has to supply the resistance. Budget the grinder before the machine, in the same way a blender's jar rather than its motor claim decides what it can actually do.
Before you buy an espresso machine
- The brew pressure the manufacturer states at the coffee, separate from the pump's bar rating.
- The boiler type and its capacity in fluid ounces, printed on the technical specification page.
- The temperature regulation method: thermostat, PID or another named control.
- The portafilter diameter in millimeters and the basket doses it is supplied with, because they fix every accessory afterwards.
- The wattage and voltage, divided to amps for the outlet the machine will use.
- The price list for gaskets, shower screens and baskets, asked for before purchase.
- The grinder's price, which belongs in the same total as the machine's.