Link to the formatting guidelines:
name: solarstrom_eigenverbrauch
unique_id: solarstrom_eigenverbrauch
unit_of_measurement: W
state: >
{% if states('sensor.tasmota_power_power_curr') | float < 0 %}
{{ states('sensor.solarstrom_energy_power') }}
{% else %}
{{ states('sensor.solarstrom_energy_power') + states('sensor.tasmota_power_power_curr') }}
{% endif %}