Knowledge / EVSE metrology
EVSE Calibration with Controlled Real Load
Compare the energy recorded by a charging station with a calibrated reference while the station supplies a controlled real load. Plan repeatable voltage, current and duration, and distinguish the metrological comparison from additional observations of charging operation.
Which calibration method fits the measurement task?
Basis and scope
The national guidance discussed below concerns Germany. A calibration result does not by itself complete legal verification.
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The measurement behind the charging bill
Compare energy while the station delivers real power.
Calibration compares the charging station’s energy reading with a calibrated reference over the same measurement interval. A controlled real load lets the operator select repeatable test conditions while the station supplies power through its charging connection.
A simple energy comparison
Illustrative values: the reference measures 10.00 kWh and the station records 10.05 kWh. The relative deviation is (10.05 − 10.00) / 10.00 × 100 = +0.5%. The result must be assessed with the measurement uncertainty and the limits of the applicable procedure.
Voltage is measured in volts (V), current in amperes (A), power in kilowatts (kW), and energy in kilowatt-hours (kWh). For DC, power is voltage × current. Energy accumulates as power flows over time.
Why controlled real load matters
Connect measurement accuracy with actual charging operation.
| Test benefit | What the setup lets you investigate |
|---|---|
| The station supplies the test power | The station’s power conversion operates under load. With the appropriate measurements, the test can investigate its electrical response during the energy comparison. |
| Defined current and duration | Hold an operating point for the required interval and observe how the measured behaviour changes as the system operates and warms up. |
| Repeatable conditions | Repeat the selected point after an adjustment, repair or update. Record the conditions so the two results can be compared. |
| A shared charging record | Relate the energy result to the session, charging requests and measured voltage or current when those channels are part of the setup. |
These are opportunities provided by the real operating condition. A calibration run alone does not establish complete electrical safety, EMC compliance or every dynamic response; those objectives need their own defined measurements and evaluation.
Specify the useful range
A maximum kW figure does not define every test point.
List voltage, current, duration and required uncertainty together. Confirm that the station, load and reference can support the complete combination.
| Voltage | Current | Power | Planning question |
|---|---|---|---|
| 150 V | 500 A | 75 kW | Can the setup hold high current at this low voltage for the required duration? |
| 1,000 V | 10 A | 10 kW | Can the reference and load work at this high-voltage, low-current point with the required uncertainty? |
Include stabilisation time, the energy interval and the repeat sequence. Peak or boost operation must be distinguished from a continuously sustainable operating point.
Easy Chester Calimera
Bring a controlled reference comparison to the installed station.
Calimera combines charging communication, reference measurement and controlled real load in a mobile setup. comframe connects the selected test conditions with the recorded measurements and report.
- Define the point
Identify the station, procedure, voltage, current and duration.
- Compare the readings
Measure the station and reference over the same interval after the required stabilisation.
- Keep a repeatable record
Save the deviation, uncertainty and conditions, then repeat the required points.
A vehicle is also a real load, but its requested current changes with battery condition, temperature and charging control. A controlled load gives the operator more direct control over repeatable points within the supported range.
Explore Calimera operating modesA common comparison question
Where does phantom power fit?
Why choose real load when phantom equipment can be smaller?
Phantom equipment applies the voltage and current needed for the metrological comparison without transferring the equivalent full charging power. This can reduce the load-equipment and energy requirement. Choose real load when the test also needs the station’s actual power-conversion operation at controlled points. Compare compatibility, installation work, duration and the required observations as well as equipment size.
Does a phantom test reproduce every operating effect?
No. In the published PTB setup, the station’s internal DC supply was disconnected. The arrangement could include cable losses, so phantom testing should not be described as always excluding them. Its metrological result does not establish identical behaviour of the complete powered station. The real/phantom comparison covered 20, 40 and 70 A at 200 and 420 V; additional phantom measurements at higher current were not equivalent high-current real-load comparisons. PTB study, pages 1–2.
Can phantom power be acceptable for legal metrology?
Yes, for a suitable charging installation and the applicable verification procedure. German guidance published in June 2026 with AGME and PTB explicitly describes field testing with phantom power, provided the installation supports the technique. This is not a blanket approval of every test device and station combination. German guidance, pages 4 and 11.
OIML G 22:2022, section 6, note 2, allows real or phantom load within its test programme; national requirements still apply. DKE lists E DIN VDE V 0122-2-100:2025-06 as a draft interface specification. Neither document alone proves that a particular station has passed its required legal verification. OIML G 22 · DKE document status.
Does calibration mean that the station is legally verified?
Calibration establishes the relationship between the station reading and a reference under stated conditions. Adjustment changes the instrument to reduce a deviation. Legal verification (Eichung) follows the requirements and procedure for the specific installation. A calibration result is useful evidence, but it does not automatically complete the legal process.
Sources and reading scope
Practical operating-point examples and Calimera workflow: comemso calibration webinar. Metrological-method boundaries: the linked PTB conference paper (CPEM 2022; repository publication 2025), OIML G 22:2022, the June 2026 German guidance and the DKE catalogue entry. The regulatory discussion concerns Germany; another country may prescribe a different procedure.
Source status checked: 7 September 2026. The examples explain test planning and do not constitute an approval of a particular charging station.
Plan an EVSE calibration application