We've revised our electricity 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 examined our own measurements.
It was important to us to develop values that represent everyday use and can make it more efficient.
This 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 doesn't have a steam function, the corresponding measurement is omitted. If a dual boiler doesn't have an option to deactivate the steam boiler, we continue the protocol without this measurement.
Otherwise, we carry out the measurement once with and once without the steam function.
measuring instruments
Performance measurement
To achieve precise and reliable values, appropriate measuring devices are essential. Therefore, we purchased three Christ CLM1000 Professional (Plus) meters. The Christ CLM1000 Professional (Plus) provides second-by-second measurements of 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 CSV.
Structure of the measurement
Preparatory work
In our first electricity comparison report, we specified a heat-up time to ensure high comparability. However, this doesn't reflect 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 in just 10?
Therefore, we try to determine empirically, as well as in consultation with the manufacturers, when the machine is actually at brewing temperature. Our discussions with the manufacturer provide us with a target value, which we then verify with our measurements (see temperature measurement protocol).
When is an espresso machine considered ready to brew?
A machine is considered ready when the target temperature of 92 °C in the portafilter is reached with the first extraction (extraction shot). A 5-second rinse with the portafilter clamped in place is performed to accelerate the warming of the portafilter (rinse shot).
Depending on the machine and function, we determine the starting temperature with and without a steam boiler.
The warm-up time is taken into account for the power measurement. After warm-up, the reference power measurement begins.
Carrying out performance measurement
We conduct the power measurement in parallel with a temperature measurement. For both measurements, the test machine must be "cold." For this purpose, a rest period of at least 6 hours is defined after the last use. The water tank is filled to its maximum capacity with water at room temperature (20-24°C). The machine is unplugged and, when the measuring devices are ready, plugged in and switched on.
Once the machine is ready after the preset time, five brews are made, each lasting 26 seconds ± 1 second (the temperature measurement procedure is covered in the Temperature Measurement section). Before the first brew, the machine rinses for 5 seconds with the portafilter clamped in place (part of the warm-up phase), and waits one minute between brews. Then, each brew is rinsed for 2 seconds before brewing. This two-second rinse is also called "flushing" and simulates the cleaning of the shower screen.
We then draw 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 draw. If the machine has the option to adjust the steam output, the steam output is always measured at maximum power.
In a final phase, energy consumption is measured while idling. For this purpose, we leave the machine running for at least 20 minutes.
One test machine, one test series
The data is collected on a test machine and in a test series. Slight control-related deviations may occur from machine to machine.
Evaluation of performance measurement
For the evaluation, we always take the timestamp and energy value from the CSV file and enter it into the measured value table.
As a rule, the data can be read as follows:
- End of heating = Espresso brewing start,
- Espresso end = Americano beginning,
- End of Americano = milk frothing beginning
- 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 time. tAA = 11:12:12 = time of heating start 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 predefined time. A comparison is then made to determine whether the first reference starts.
Calculation: EA = EAE - EAA
Example: 0.1000 kWh = 0.1000 kWh - 0
Espresso 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
Consumption steam / milk frothing
Here we also note the value we set for the steam draws. 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 “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
When calculating the cost of an espresso, as well as a cappuccino, we included the heating time. We conducted a survey among our community, in which 2,700 people participated. Typical usage behavior was examined. One finding related to the regular heating and brewing of coffee: in most cases, the coffee is heated and then brewed one or two times.
Therefore, we include the heating time in the consumption bill for one use.
Calculation of 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 a 1-minute break between extractions. To ensure comparability with the older videos, we still provide this value as the EKM.
Please note, however, that the older values may be comparatively high for machines with a faster heat-up time.
Calculation of the coffee maker protocol: EKM = EA + EE5
Feedback and measurement standard
This measurement protocol has been tested in practice several times and has evolved based on feedback from espresso machine manufacturers. Thanks to Holger Dreißig of Xenia Espresso and Julian Thomas and Patrick Lieser of Profitec for their detailed feedback.
Xenia uses the performance measurement protocol to optimize and develop benchmarks for other espresso machines. Profitec and ECM also use the measurement protocol in development and to collect benchmarks.
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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