Zero feed-in with FRITZ! Smart Energy 250 and Anker Solix in Home Assistant

Many owners of balcony solar power systems with storage want to minimize their feed-in to the public grid. Ideally, they only supply as much power as is actually needed in the household. Current systems often use special smart meters that record electricity consumption almost in real time and adjust the inverter's output accordingly. However, this requires installation by an electrician, and I wanted to avoid the associated costs for the time being.

Therefore, I used a different approach and connected the existing devices together. Using the FRITZ! Smart Energy 250*, one Anker SOLIX solar bank* and Home Assistant* I have implemented a functioning zero feed-in system, and this without an additional smart meter in the fuse box.

The initial situation

I have been using the FRITZ! Smart Energy 250 for reading my digital electricity meter. The sensor is placed directly onto the optical D0 interface of the electricity meter and transmits the measured values via DECT to the FRITZ!Box*.

The data is then available via FRITZ!SmartHome in Home Assistant available and can be used both in Energy Dashboard It can be visualized and used for automation.

For electricity generation, I use a balcony power plant with integrated storage and a maximum feed-in power of 800 watts. In my case, a Anker SOLIX Solar Bank 2 E1600 Pro* for use. Home Assistant now also supports other models such as the Anker Solar Bank 2 E1600 AC* as well as the Anker Solar Bank 3 E2700*. The list of supported devices is continuously being expanded, and current models such as the Anker SOLIX Solar Bank 4 Pro* will also be supported shortly.

Operating principle of zero feed-in in Home Assistant

The entire system is controlled via automation in Home Assistant. The FRITZ! Smart Energy 250 serves as a sensor for the current power flow at the grid connection point.

sensor.fritz_smart_energy_250_power

The power measured by the electricity meter is compared with the currently set feed-in power of the balcony power plant.

sensor.solarbank_2_e1600_pro_ac_hausabgabe

From this difference, Home Assistant calculates a new target value, which is then transferred to the Anker SOLIX solar bank.

number.solarbank_2_e1600_pro_system_feed-in specification

The feed-in power is continuously adjusted. This is triggered by changes in the power output of the FRITZ! Smart Energy 250. A 10-second delay is also integrated to prevent unnecessary adjustments.

The goal of the automation is to keep grid consumption or feed-in as close to 0 watts as possible. A tolerance of ±5 watts was defined for this purpose, so that the solar bank does not react to every minor fluctuation.

abs > 5 

The power input can be flexibly adjusted between 0 and 800 watts.

 {{ [current_value + (stromverbrauch ), 800] | min }}
 {{ [current_value + stromverbrauch, 0] | max }}

The sensor and entity names used in this example are from my installation and may therefore be different in yours. You can find the correct names directly in the device and entity details of Home Assistant.

The complete YAML code for my automation can be added to Home Assistant under Automation. Create a new automation and then select "Edit in YAML" via the three dots.

alias: Zero feed-in with Anker Solix Solarbank E1600 description: Attempts to keep power consumption at 0 watts with Anker Solix Solarbank E1600 triggers: - trigger: state entity_id: - sensor.fritz_smart_energy_250_leistung enabled: true conditions: [] actions: - repeat: while: - condition: template value_template: > {% set stromverbrauch = states('sensor.fritz_smart_energy_250_leistung') | float(0) %} {{ stromverbrauch | abs > 5 }} sequence: - action: number.set_value target: entity_id: number.solarbank_2_e1600_pro_system_einspeisevorgabe data: value: > {% set stromverbrauch = states('sensor.fritz_smart_energy_250_leistung') | float(0) %} {% set current_value = states('sensor.solarbank_2_e1600_pro_ac_hausgabe') | float(0) %} {% if power consumption > 0 %} {{ [current_value + (power consumption ), 800] | min }} {% else %} {{ [current_value + power consumption, 0] | max }} {% endif %} - delay: hours: 0 minutes: 0 seconds: 10 milliseconds: 0 mode: single

💬 I look forward to hearing about your experiences, optimization suggestions, and ideas for improving automation in the Comments.

Improvement potential of DIY zero feed-in

The biggest criticism of the FRITZ! Smart Energy 250 is its comparatively low update rate. Data is typically only transmitted to Home Assistant every 30 to 60 seconds.

This is obviously not ideal for very fast decisions. However, in practice, the solution has proven to work surprisingly well nonetheless.

The fluctuations in the regulation are clearly visible in the display of the measured power of the FRITZ! Smart Energy 250.

Typical appliances like refrigerators, consumer electronics, lighting, or computers usually don't cause extremely rapid load changes. The solar power bank can therefore reliably balance a large portion of daily electricity consumption. Short-term load peaks, for example from a kettle, oven, or induction cooktop, cannot be completely compensated for due to the delayed transmission of measured values. In these cases, there is a brief draw from the grid before the control system adjusts.

Despite this limitation, the solution performs well in everyday use. A particularly interesting aspect is that existing hardware can continue to be used without having to install additional components.

Conclusion

Even though the FRITZ! Smart Energy 250 wasn't originally designed for controlling balcony solar panels, it works surprisingly well as a data source for simple zero-feed-in when used with Home Assistant. While the update rate of approximately 30 to 60 seconds doesn't prevent perfect real-time control, the accuracy is perfectly adequate for many applications. Anyone who already owns a FRITZ! Smart Energy 250 and an Anker SOLIX solar bank can implement intelligent power management with minimal effort and significantly reduce their feed-in to the public grid. In my daily life, the solution works reliably and demonstrates the flexibility of Home Assistant.

Source/Photo: (Amazon / solar modules-gladbeck / HA anchor / Chrissmart)