We have revised our electricity measurement protocol to ensure greater comparability and create transparency. To this end, we have taken a closer look at how energy labels are measured and have critically examined our own measurements.
It was important to us to develop values that represent everyday usage and can make it more efficient.
This article explains how we measure, how the results are arrived at, and introduces our equipment. This is how we now measure espresso machines with all technologies. If a machine does not have a steam function, the corresponding measurement is omitted. If a dual boiler machine does not have an option to switch off the steam boiler, we proceed without this measurement in the protocol.
Otherwise, we carry out the measurement once with and once without the steam function.
Measuring instruments
Power measurement
Appropriate measuring instruments are the prerequisite for achieving precise and reliable values. For this reason, we have purchased three Christ CLM1000 Professional (Plus) units. The Christ CLM1000 Professional (Plus) provides per-second readings for power consumption and energy usage at a resolution of one-tenth of a watt-hour. This corresponds to 0.0 Wh or 0.0000 kWh.
The device transfers the measured values via USB, and we can save and analyze them as a CSV file.
Measurement setup
Preparation
In our first power comparison protocol, we defined a heat-up time to achieve high comparability. However, this does not correspond to actual usage and penalizes machines that heat up and are ready to brew faster. Why wait 25 minutes at home when the machine is ready after just 10 minutes?
Therefore, we try to determine when the machine is actually at brewing temperature, both empirically and in consultation with the manufacturers. Communication with the manufacturer gives us a target value, which we then verify with our measurements (see the temperature measurement protocol for this).
When is an espresso machine considered temperature-ready?
A machine is considered ready when the target temperature of 92 °C is reached in the portafilter with the first extraction (extraction shot). A 5-second pre-rinse with the portafilter inserted is performed to accelerate the heating of the portafilter (rinse shot).
Depending on the machine and function, we determine the start temperature with and without the steam boiler.
The heating time is taken into account for the power measurement. The extraction power measurement begins after the heating phase.
Conducting the power measurement
We perform the power measurement in parallel with a temperature measurement. The test machine must be “cold” for both measurements. For this, a rest period of at least 6 hours since the last use is defined. The water tank is filled with water at room temperature (20 - 24 °C) up to the maximum volume. The machine is unplugged and, when the measuring devices are ready, it is plugged in and switched on.
If the machine is ready after the predetermined time, 5 extractions of 26 s ± 1 s each are performed (the sequence for the temperature measurement is covered in the Temperature Measurement section). Before the first extraction, a 5 s rinse is carried out with the portafilter inserted (part of the warm-up phase), and there is a one-minute wait between extractions. Subsequently, a 2 s rinse is performed before each extraction, followed by the extraction itself. The two-second rinse is also called “flushing” and simulates cleaning the shower screen.
After that, we extract 5 x 70 g ±5 g of hot water from the hot water dispenser to simulate an Americano. Here, too, we wait one minute after each extraction. If the machine has the option to set the steam power, then the steam extraction is always measured at maximum power.
In a final phase, the energy draw is measured in “idle” mode. For this purpose, we leave the machine on for at least 20 minutes.
One test machine, one test series
Data collection is carried out on one test machine and in one test series. Slight control-related variations may occur from machine to machine.
Evaluation of the power measurement
For the evaluation, we always take the timestamp and energy value from the CSV file and enter them into the measurement table.
As a rule, the data should be read as follows:
- End of heating = Start of espresso extraction,
- End of espresso extraction = Start of Americano,
- End of Americano = Start of milk frothing
- End of milk frothing = Start of keeping warm
However, if there were pauses during the measurement, these are taken into account in the evaluation. Data points here always consist of two values: timestamp t and consumption E at that time. tAA = 11:12:12 = Time heating starts and EAA = 0 = Heating start
Heating up
We take the first data point from the measurement and the data point that can be taken after the predetermined time. A check is also performed here to see if the first extraction starts then.
Calculation: EA = EAE - EAA
Example: 0.1000 kWh = 0.1000 kWh - 0
Consumption of espresso extractions
Calculation: EE5 = EEE - EEA
Example: 0.0077 kWh = 0.1200 kWh - 0.1023 kWh
Calculation: EE1 = EE5 / 5
Example: 0.00154 kWh = 0.0077 kWh / 5
Hot water consumption
Calculation: EA1 = EHE - EHA
Example: 0.0050 kWh = 0.1250 kWh - 0.1200 kWh
Steam / milk frothing consumption
Here we also note the value we set for the steam extractions. For example: tD = 25 s
Calculation: ED5 = EDE - EDA
Example: 0.0100 kWh = 0.1250 kWh - 0.1200 kWh
Calculation: ED1 = ED5 / 5
Example: 0.0020 kWh = 0.0100 kWh / 5
Keeping warm consumption
By keeping warm, we mean “ready for immediate use,” i.e., neither standby nor energy-saving mode.
Calculation: EW = EWE - EWA
Example: 0.0150 kWh = 0.1450 kWh - 0.1250 kWh
Calculation: EW60 = EW / (tWE - tWA) * 3600 s
Example: 0.1800 kWh = 0.0150 kWh / (14:10:00 - 14:05:00) * 3600 s
Consumption of espresso, Americano and cappuccino
For the calculation of an espresso, as well as for the calculation of a cappuccino, we have included the heating time. We conducted a survey in our community in which 2700 people participated. Typical usage behavior was examined. One insight related to the regular heating and brewing of coffee: in most cases, the machine is heated up and then one to two extractions are performed.
Therefore, we include the heating time in the consumption calculation for an extraction.
Calculation espresso: EE = EA + EE1
Calculation cappuccino: EC = EA + EE1 + ED1
Consumption Kaffeemacher protocol (EKM)
In the older videos, our consumption figures always refer to a heating time of 25 minutes and 5 extractions with a 1-minute pause between extractions. To ensure comparability with the old videos, we still provide this value as EKM.
However, note here that the older values may appear too high in comparison for machines with a faster heating time.
Calculation Kaffeemacher protocol: EKM = EA + EE5
Feedback and measurement standard
This measurement protocol has been checked several times in practice and has evolved through feedback from espresso machine manufacturers. Thanks for the differentiated feedback to Holger Dreißig from Xenia Espresso as well as Julian Thomas and Patrick Lieser from Profitec.
Xenia uses the power measurement protocol for optimization and to develop comparative values for other espresso machines. Profitec and ECM also use the measurement protocol in development and for collecting comparative values.
Do you have any questions about our measurements? Have you already measured your own machines? We look forward to your feedback and comments.
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