Choosing a Domestic Espresso Machine

An espresso machine has a seemingly simple task - to pump water through ground coffee at a temperature of around 93˚c and a pressure of 9 bar in 20 to 30 seconds.
There is a secondary function of producing steam for heating and foaming milk.
So why is there such a range of machines and range of prices (from £50 to £2000 and beyond)?
What do you get for your money?
How much do you need to spend to make a decent espresso?

There are a couple of key features that distinguish the good from the mediocre, and perhaps the most important is:

Temperature Stability
Supplying water at the correct temperature is essential for espresso. A commercial espresso machine is designed to be left on all day; it has a large boiler and a large amount of metal which, once warmed up, will keep a stable temperature all day long. Many commercial machines also heat the group (the bit the water passes through which the portafilter - the part that holds the ground coffee - locks onto) to help keep temperature stable.
But in a smaller domestic machine it is much more difficult to maintain temperature - it will continually heat up and cool down as coffee is made.

Brew Temperature and Steam Temperature

You may have noticed already that the task of the espresso machine is not so straight forward - it has to supply water at for the coffee but at near boiling point for the steam. How is is able to do this?

1. Single Boiler Dual Function

Most favoured on this forum are the Gaggia Classic (approx. £169) and the Rancilio Silvia (£349)
The very cheapest espresso machines (under £100), despite their appearances, are really like a version of the Bialetti or Moka stove top pots; rather than using a pump, hot water is heated up by an electric element and steam pressure passes it though the coffee. This inevitably means the water is too hot and scalds the coffee. We will not be considering these.

The simplest ‘proper’ domestic espresso machines work like this: a small thermostat-controlled boiler heats up the water to brew temperature, the pump forces it through the coffee. To make steam to foam your milk, you switch to a second thermostat and wait until the water reaches boiling point.

Immediately we can see two problems with this system: firstly, you have to wait a few minutes between brewing and steaming for the boiler to get hotter and, perhaps more importantly, the temperature in the boiler is rising and falling all the time - after you have made steam, the boiler is going to be substantially hotter than it was before and it could take some time to return to the correct temperature for coffee.

The Classic is solid, reliable and parts are easy to replace. It is a very popular machine and it easy to pick up a decent one second hand. The Silvia is generally regarded as a slightly better machine - more solid and better temperature stability - but the current price differential between it and the Classic mean that, arguably, it is not such good value for money. There are many other single boiler machines on the market, many of which look more stylish than the Gaggia or Rancilio but none of them are going to make better coffee or offer better long term value for money.

Both the Classic and the Silvia can upgraded with a PID control. The PID (stands for Proportional/Integral/Derivative) is an electronic device that, rather than switching power to the boiler on and off like a simple thermostat, supplies power in a series of pulses that get briefer as the boiler approaches the correct temperature. The PID control also allows you to experiment with different temperatures for different coffees.

2. Heat Exchanger (HX)

Popular HX machines include the Fracino Cherub (approx. £650), the Expobar Leva Office (£900), and the Rocket Giotto and Cellini (£1200 to £1400)

The heat exchanger has been used for decades in commercial machines. In an HX machine there is one heating element and one boiler, which superheats water under pressure so it can deliver steam on demand. Temperature of the water is usually regulated by a pressurestat (the pressure of the water in the boiler is directly related to its temperature). The brew water does not come directly from the boiler but from a copper tube that passes through the boiler.

A variation on this design (often but not necessarily incorporated into HX system) is the thermosiphon, which uses principles of convection (hot water rises/cold water sinks) to pass water directly from the boiler to the group which acts as a heat sink to reduce this superheated water to brew temperature. If the group gets too hot or too cold, water in the thermosiphon will circulate and bring it back to the correct temperature.

The E61 group is often found on HX machines (called so because it was developed by Faema in 1961 - the year of the eclipse). Although initially a commercial design, it is now found on many prosumer machines. In the E61 group water is circulated through the body of the group itself, maintaining a stable temperature. It also allows for pre-infusion, which lets hot water flow into the coffee grinds just before extraction takes place enabling a better extraction.

All the machines mentioned above are solidly made and will produce excellent coffee. The Italian machines (like Rocket and Izzo) tend to win on sheer looks, but the British (Fracino) and Spanish (Expobar) machines offer excellent value for money.

All the machines mentioned so far use an electric pump to force water through the coffee. Pumps come into two basic types - vibratory and rotary. Both work well; the vibratory pumps are cheaper, rotary pumps quieter.

3. Dual Boiler

Popular Dual Boiler machines include the Fracino Piccino (£600), Expobar Leva Dual (£1100), La Spaziale Vivaldi II (£1500) and the Izzo Alex Duetto (£1900)

A increasingly popular solution is to have one boiler supplying the water for brewing coffee and a separate boiler supplying water for steam. Both boilers have their own heating elements. This creates a slightly more complicated and more costly system, but it does mean the temperature of the brew water can be controlled completely independently of the steam system. E61 type groups are also found on Dual Boiler machines.

Both HX and Dual Boiler machines can maintain stable temperature and steam milk at the same time as they brew coffee and produce first rate espresso and cappuccino. Some machines, like the Expobar Leva Dual and the Alex Duetto have PID controls to maintain and adjust temperature accurately.

Although in principle, Dual Boiler may seem like a better solution than HX machines, in practice both can produce excellent coffee. It really comes down to the particular design of the machine, and some HX designs may have better temperature stability and steam power than Dual Boiler machines.

But there is an alternative to pump machines.

4. Lever Machines

Popular lever machines include the Pavoni Europiccola (£300-£500), the Ponte Vecchio Lusso (£650 - £800), the Elektra Micocasa (£1000), the Olympia Cremina (£2750) and the Londinium I (£1600)

Lever machines use a manual lever connected to a piston to force water through the coffee. This is traditional method that preceded electric pumps and is still favoured in southern Italy and is now having something of a resurgence.

Advocates of lever machines claim that the column of water the piston pushes through the coffee extracts the very best from the coffee and the mechanical design of the system means temperature of water is reduced as the piston descends, reducing the undesirable elements that remain in the coffee as the extraction progresses. Lever machines have the additional advantage of being extremely reliable and almost silent.

In manual lever machines the lever is connected directly to the piston, in spring-driven machines it is the spring that does the work (lifting the lever tensions the spring ready for the next extraction). Like dual boiler and heat exchanger designs, lever machines will supply steam without waiting for the boiler to reheat - either by basic mechanical design (the mass of the group and cylinder cooling the boiler water to the correct temperature) or by using thermosiphon principles. The best lever machines also exhibit excellent temperature stability but, with some of the more inexpensive machines, keeping the temperature steady can be a bit hit or miss (or, some would say, an acquired skill).

The high price of some new lever machines is offset by the fact, because of simplicity of design and quality of engineering, they can literally last a lifetime.

In conclusion: How much difference does it really make?

1. ALL the above machines are capable of making good espresso and cappucino, just on some it is easier than others. Generally speaking, the more sophisticated machines give more consistent results - it may take a bit more skill and fiddling to get a predictable result out of a smaller machine. Milk steaming is also easier on a bigger, more powerful machine.

2. The more sophisticated machines not only are likely to give you more consistent results, they will also allow you to fine-tune the extraction to get the very best out of the beans. This can make the difference between good and great coffee.

3. The bigger machines also allow you produce more coffees in a row and steam more milk without having to wait for the machine to heat up or cool down. If you are holding a dinner party and want to make half a dozen or more cappucinos, you may find it so tedious on a small machine that you end up offering them another form of coffee altogether.

Article written by RoloD (Roland Denning November 2012)