We have revised our power measurement protocol to ensure greater comparability and transparency. To do this, we took a closer look at how energy labels are measured and critically re-evaluated our own measurements.
It was important for us to develop values that represent everyday use 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 does not have the option to switch off the steam boiler, we proceed with the protocol without this measurement.
Otherwise, we perform the measurement once with and once without the steam function.
Measuring Instruments
Power Measurement
To obtain precise and reliable values, appropriate measuring instruments are essential. Therefore, we purchased three Christ CLM1000 Professional (Plus) devices. The Christ CLM1000 Professional (Plus) provides second-by-second measurements for power consumption and energy consumption with a resolution of one tenth of a watt-hour. This corresponds to 0.0 Wh or 0.0000 kWh.
The measuring device transmits the measured values via USB, and we can save and evaluate them as a CSV.
Measurement Setup
Preparation
In our first power comparison protocol, we set a warm-up time to achieve high comparability. However, this does not reflect actual use and penalizes machines that heat up and are ready for brewing more quickly. Why wait 25 minutes at home if the machine is ready after only 10 minutes?
Therefore, we empirically try to determine when the machine is truly at brewing temperature, also in consultation with the manufacturers. The exchange with the manufacturer gives us a target value, which we then 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 shot (extraction shot). A preliminary 5-second flush with the portafilter clamped in is performed to accelerate the heating of the portafilter (flush shot).
Depending on the machine and its function, we determine the starting temperature with and without the steam boiler.
The heating time is taken into account for the power measurement. After heating, the extraction power measurement begins.
Performing the Power Measurement
We perform the power measurement in parallel with a temperature measurement. For both measurements, the test machine must be "cold." A rest period of at least 6 hours since the last use is defined for this. The water tank is filled with water at room temperature (20 - 24 °C) up to its maximum volume. The machine is unplugged and, when the measuring devices are ready, it is plugged in and switched on.
Once the machine is ready after the predetermined time, 5 extractions of 26 s ± 1 s each are performed (the process for temperature measurement is covered in the temperature measurement section). Before the first extraction, a 5-second flush is performed with the portafilter in place (part of the warm-up phase), and there is a one-minute wait between extractions. Subsequently, before each extraction, a 2-second flush is performed, followed by the extraction. The two-second flush is also referred to as "flushing" and simulates cleaning the shower screen.
After that, 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 dispense. If the machine has the option to adjust steam power, then steam dispensing is always measured at maximum power.
In a final phase, the energy consumption in "idle" is measured. For this purpose, we leave the machine on for at least 20 more minutes.
One Test Machine, One Test Series
Data collection is performed on one test machine and in one test series. Slight control-related deviations may occur from machine to machine.
Evaluation of Power Measurement
For the evaluation, we always take the timestamp and energy value from the CSV file and enter them into the measurement table.
Typically, the data can 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 of heating start and EAA = 0 = heating start
Heating
We take the first data point from the measurement and the data point that can be taken after the previously defined time. A comparison is then made here to see if the first extraction also starts at that point.
Calculation: EA = EAE - EAA
Example: 0.1000 kWh = 0.1000 kWh - 0
Espresso Extraction Consumption
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 steam dispenses. 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
Keep Warm Consumption
By "keeping warm" we mean "immediately ready for 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
Espresso, Americano and Cappuccino Consumption
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. The typical usage behavior was examined. One insight related to the regular heating and brewing of coffee: in most cases, it is heated up to then perform one to two extractions.
Therefore, we include the heating time in the consumption calculation for one extraction.
Espresso calculation: EE = EA + EE1
Cappuccino calculation: EC = EA + EE1 + ED1
Kaffeemacher Protocol Consumption (EKM)
In older videos, our consumption figures always refer to a warm-up time of 25 minutes and 5 extractions with 1 minute pause between extractions. To maintain comparability with the old videos, we still state this value as EKM.
Please note, however, that older values for machines with faster warm-up times may be disproportionately high in comparison.
Kaffeemacher Protocol calculation: EKM = EA + EE5
Feedback and Measurement Standard
This measurement protocol has been thoroughly reviewed in practice and has evolved through feedback from espresso machine manufacturers. Thanks for the detailed feedback to Holger Dreißig from Xenia Espresso and Julian Thomas and Patrick Lieser from Profitec.
Xenia uses the power measurement protocol for optimization and to develop comparative values with 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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