Short Definition
In technical usage, the term smart meter frequently refers to a digital, communication-enabled energy meter that automatically records electrical measurements and makes them available to other systems. In the German regulatory context, this must be distinguished from an intelligent metering system, which consists of a modern metering device and a smart meter gateway.
In PV, battery storage and EMS applications, a smart meter frequently serves as the central measuring point for grid consumption, grid feed-in, generation or site consumption.
Smart meters at a glance
- Smart meters digitally record energy and power values and make them available to other systems.
- An EMS uses current measurements for applications such as zero feed-in control, peak shaving or the control of a battery energy storage system (BESS).
- A communication-enabled operational meter is not automatically an intelligent metering system in the regulatory sense.
- Measurement quality, update rate, communication latency and correct installation are crucial for active control applications.
How does a smart meter work?
A smart meter measures current and voltage. Depending on the meter and the plant capacity, current is measured either directly or via external current transformers. Based on these measurements, the device calculates values including active power, reactive power, energy volumes and power factor. Many devices also provide phase-specific values for voltage, current, power and power factor, as well as the grid frequency.
For local data transmission, interfaces and protocols such as Modbus TCP via Ethernet, Modbus RTU via serial interfaces, M-Bus or manufacturer-specific protocols may be used. Data can also be transmitted to remote systems via a gateway and communication channels such as Ethernet or mobile networks.
If the smart meter is located at the grid connection point, it measures the energy flow between the site and the public grid. Depending on the meter, plant configuration and technical requirements, grid power is evaluated either as an aggregated value across all phases or separately for each phase.
An EMS uses this measurement as a feedback variable. For zero feed-in control, for example, the controller compares the measured grid power with the setpoint and adjusts the PV output or the charging and discharging power of the BESS accordingly. The smart meter provides the measurement data but does not usually perform the higher-level optimisation or coordination of the connected assets.
Where are smart meters used?
Typical applications include:
- Control at the grid connection point: Measurement of grid consumption and feed-in for zero feed-in control, feed-in limitation, self-consumption optimisation or peak shaving.
- Consumption and load analysis: Determination of load profiles and energy consumption for individual plant areas or consumers.
- Submetering concepts: Separate measurement of machinery, sections of a building, EV charging infrastructure or other groups of consumers.
- Monitoring and billing: Visualisation of energy flows and detection of deviations, as well as the provision of billing-relevant measurements—provided that the metering system is suitable for the respective billing purpose and used in compliance with the applicable requirements.
Requirements and limitations
For active control tasks, the update rate, measurement accuracy and communication latency must be suitable for the required control dynamics. Significantly delayed, incorrect or implausible measurements can result in inaccurate or unstable setpoint corrections.
The correct measuring point, phase sequence, current transformer installation direction and configured transformation ratio are equally important. The sign convention for grid consumption and feed-in must also be clearly coordinated between the meter and the controller.
Depending on the country and application, specific metrological and calibration requirements apply to billing purposes. In addition to the meter itself, the metering concept, installation and compliant operation are decisive. An operational meter used solely for monitoring and control does not automatically fulfil these requirements.
If communication fails, an active plant controller also requires a defined fallback strategy.
How does EcoPhi integrate smart meters?
EcoPhi can integrate smart meters and energy meters from different manufacturers via available communication interfaces. Measurements can be stored, visualised, evaluated for alarms and used as feedback variables for local EMS functions.
Possible applications include controlling PV and BESS at the grid connection point and monitoring individual consumers or plant areas. The specific scope of functions depends on the meter model, available data points, measurement rate, communication interface and the respective project architecture.
Smart meter summary
A smart meter provides digital energy and power measurements for monitoring, analysis and plant control. In addition to measurement accuracy, fast and reliable communication and correct installation and configuration are essential for EMS control functions. A communication-enabled operational meter must be clearly distinguished from an intelligent metering system in the regulatory sense.
Frequently asked questions
Is every digital energy meter a smart meter?
The term is not used consistently. In technical usage, it frequently refers to a communication-enabled digital meter. An intelligent metering system in the German regulatory sense additionally includes a smart meter gateway.
Can a smart meter control a PV plant or BESS?
Smart meters generally provide the required measurements. An EMS or another plant controller calculates and transmits the setpoints.
Can an operational meter be used for billing?
Only if the entire metering system is suitable for the respective billing purpose and complies with the applicable metrological and calibration requirements.