We have revised our power measurement protocol to ensure greater comparability and create transparency. To do this, we took a closer look at how energy labels are measured and critically questioned our own measurements.
It was important to us to develop values that represent everyday usage and can make it more efficient.
The article explains how we measure, how the results are obtained, and introduces our equipment. 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 has no option to shut off the steam boiler, we continue without this measurement in the protocol.
Otherwise, we perform the measurement once with and once without the steam function.
Measuring Instruments
Power Measurement
To achieve precise and reliable values, appropriate measuring instruments are essential. Therefore, we have acquired three Christ CLM1000 Professional (Plus) devices. The Christ CLM1000 Professional (Plus) provides second-by-second measurement values for power consumption and energy usage with a resolution of one tenth of a watt-hour. This corresponds to 0.0 Wh or 0.0000 kWh.
The measuring instrument transmits the measurement values via USB and we can save and evaluate them as CSV.
Measurement Setup
Preparation
In our first power comparison protocol, we set a heat-up time to achieve high comparability. However, this does not reflect actual usage and penalizes machines that heat up faster and are ready to brew. Why should you wait 25 minutes at home when the machine is ready after 10 minutes?
Therefore, we try to determine empirically and in consultation with the manufacturers when the machine is really at brewing temperature. The exchange with the manufacturer gives us a target value, which we verify with our measurements (see temperature measurement protocol).
When is an espresso machine considered temperature-ready?
A machine is considered ready when the target temperature of 92 °C in the portafilter is reached with the first extraction (extraction shot). A prior 5-second purge with the portafilter installed is performed to accelerate the heat-up of the portafilter (purge shot).
Depending on the machine and function, we determine the start temperature with and without steam boiler.
The heat-up time is taken into account for the power measurement. After heating up, the extraction power measurement begins.
Conducting the Power Measurement
We conduct the power measurement in parallel with a temperature measurement. For both measurements, the test machine must be "cold". For this, a rest period of at least 6 hours from last use is defined. The water tank is filled with water at room temperature (20 - 24 °C) to maximum volume. The machine is unplugged and, when the measuring instruments are ready, is plugged in and switched on.
Once the machine is ready after the predetermined time, 5 extractions of 26 s ± 1 s are made (procedure for temperature measurement is covered in the Temperature Measurement section). Before the first extraction, a 5 s purge is performed with the portafilter installed (part of the heat-up phase) and one minute is waited between extractions. Then before each extraction 2 s is purged and then extracted. The two-second purge is also called "flushing" and simulates cleaning of the shower screen.
Then we dispense 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 ability to adjust the steam output, the steam extraction is always measured at maximum power.
In a final phase, the energy consumption in "idle" mode is measured. For this purpose, we leave the machine on for at least 20 minutes.
One test machine, one test series
Data collection is performed on one test machine and in one test series. There may be slight control-related variations from machine to machine.
Evaluation of Power Measurement
For evaluation, we always take the timestamp and energy value from the CSV file and enter them in the measurement table.
Generally, the data should be read as follows:
- End heat-up = Espresso extraction start,
- Espresso extraction end = Americano start,
- End Americano = Milk frothing start
- Milk frothing end = Keep warm start
However, if there were pauses during the measurement, these are taken into account in the evaluation. Data points always consist of two values: timestamp t and consumption E at that point. tAA = 11:12:12 = time point heat-up start and EAA = 0 = heat-up start
Heat-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 made here to see if the first extraction also starts then.
Calculation: EA = EAE - EAA
Example: 0.1000 kWh = 0.1000 kWh - 0
Consumption 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
Consumption Hot Water
Calculation: EA1 = EHE - EHA
Example: 0.0050 kWh = 0.1250 kWh -0.1200 kWh
Consumption Steam / Milk Frothing
Here we also note the value we have 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
Consumption Keep Warm
By keep warm we understand "immediately ready to use", meaning 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 Espresso, Americano and Cappuccino
For the calculation of an espresso, as well as for the calculation of a cappuccino, we have included the heat-up time. We conducted a survey in our community with 2700 participants. This examined typical usage behavior. One finding related to regularly heating up and extracting coffee: in most cases, the machine is heated up and then one or two extractions are performed.
Therefore, we include the heat-up time in the consumption calculation for one extraction.
Calculation Espresso: EE = EA + EE1
Calculation Cappuccino: EC = EA + EE1 + ED1
Consumption Coffee Maker Protocol (EKM)
In the older videos, our consumption figures always refer to a heat-up time of 25 minutes and 5 extractions with 1 min. pause between extractions. So that we can also have comparability with the old videos, we also provide this value as EKM.
Please note here that the older values can be comparatively too high for machines with faster heat-up times.
Calculation Coffee Maker Protocol: EKM = EA + EE5
Feedback and Measurement Standard
This measurement protocol has been tested several times in practice and has evolved through feedback from espresso machine manufacturers. Thanks for the detailed feedback to Holger Dreißig from Xenia Espresso as well as Julian Thomas and Patrick Lieser from Profitec.
Xenia uses the power measurement protocol to optimize and develop comparison values with other espresso machines. Profitec and ECM also use the measurement protocol in development and for establishing comparison values.
Do you have questions about our measurements? Have you already measured your own machines? We look forward to your feedback and comments.
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The latest publications with the new power measurement
An overview of all previous power measurements (as of 07.11.24)
