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External Limit (§14a, §9)

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Grid operators and higher-level energy management systems can externally limit the power consumption and feed-in of your installation. The following use cases are supported:

  • § 14a EnWG (German regulation): Temporary power reduction and dimming of consumers by the grid operator
  • § 9 EEG (German regulation): Curtailment of solar installations in case of grid overload
  • EMS integration: Applying limits from other energy management systems

Background

Controllable Consumption Devices (§ 14a EnWG)

§ 14a of the German Energy Industry Act (EnWG) regulates grid-friendly control of controllable consumption devices (SteuVE). Grid operators can temporarily reduce the power of large consumers such as wallboxes, heat pumps or battery storage systems in the event of grid overload.

Important points:

  • Affects consumers from 4.2 kW power
  • Control via Smart Meter Gateway and control box

Feed-in Management (§ 9 EEG)

According to § 9 of the Renewable Energy Act (EEG), grid operators can curtail the feed-in of renewable energy installations in the event of imminent grid overload. This mainly affects larger solar installations, but can also become relevant in the residential sector.

When evcc receives a curtailment signal, the curtailment level is distributed to all curtailable inverters as a percentage and applied directly at the device. FNN control boxes signal staged limits (60%, 30%, 0%), which are applied as-is. Watt-based limits (e.g. via EEBus) are converted to a percentage based on the installed generator power. Inverters without fine-grained control are switched off completely while the limit is active. The active limit is shown in the UI; full production resumes once the signal clears.

Setup

Configuration is done via Configuration → External Limit. Pick one of the integrations listed below and enter its parameters. Alternatively, you can create a user-defined integration, e.g. for a connection via a single switch contact (relay).

To apply the consumption limit to your charging points, set up circuits in Load Management. An active limit then caps the top-level circuit, indicated by a "Consumption limited" hint on the Load Management card. Active limits are shown on the External Limit card and on the main page.

Pairing for EEBus Integrations

With integrations using the EEBus protocol, the control box communicates directly with evcc and automatically transmits the power limit. Control box and evcc need to be paired once:

  1. In the control box: Add evcc as HEMS. The SKI and IP address of evcc are shown under Configuration → EEBus.
  2. In evcc: Enter the control box SKI in the integration. You can find it in the control box documentation or its web interface.

Integrations

Generic integrations
FNN-Steuerbox via EEBus LPC&LPP (§ 14a EnWG, § 9 EEG)FNN-Steuerbox via GPIO (§ 14a EnWG, § 9 EEG)
Awatt Electronic
HEMS PRO (EEBus)HEMS PRO (FNN-Schaltkontakte)

How It Works

In normal operation, evcc charges without external power limitation. The charging points operate with their normal configuration and are coordinated by additional Load Management restrictions if applicable.

When the grid operator sends a reduction signal:

  1. FNN control box: The W4 contact is closed, evcc activates the configured consumption limit
  2. EEBus: The control box digitally transmits the calculated total limit
  3. Relay: The contact is closed, evcc activates the configured power limit

The limit caps the top-level Load Management circuit; all charging points assigned to circuits are reduced accordingly. If total consumption is too high, charging processes can also be stopped. The control affects all modes (Solar, Min+Solar, Fast).

Battery control during reduction:If active battery control is configured and grid charging of the home battery is active, this is automatically paused. The battery is set to "hold" mode so that it no longer discharges. Charging the battery from solar surplus is usually still possible. After the power reduction ends, grid charging automatically resumes.

When a control limit is active, a banner with control notice is displayed on the main page in evcc. Consumption limit and feed-in curtailment are shown separately.

Logging

All limitation requests from the grid operator are automatically documented. The log data can be downloaded as a CSV file under Configuration → External Limit.

Each entry contains:

  • Start and end time of the limitation
  • Type of control (consumption reduction or feed-in curtailment)
  • Measured grid power at the start of the limitation
  • Set power limit

This documentation can be provided to the grid operator upon request to verify compliance with control requests.

Controlling Additional Consumers

In addition to charging points, other controllable consumers can also be integrated into German § 14a load management. This applies e.g. to heat pumps or battery storage systems that are connected via EEBus or configured as meters with an additional relay output.

The control takes into account the current power consumption of all controllable consumers. This automatically includes all charging points and all meters with corresponding switching outputs or EEBus interface with LPC use case as other consumers.

First, all other consumers are dimmed. The remaining power is then distributed to the active charging points. Due to flat dimming of other consumers, the available charging power for active charging points can in exceptional cases even be higher than in normal state. If throttling the charging points including dimming all other consumers is not sufficient, charging processes at charging points are interrupted.

Further Information