Tesla Powerwall to trigger HWS

Hello all.

First post on first Home assistant journey.

have a tesla powerwall and solar and want to use excess solar to heat a small hot water unit.

hot water has 1800w element, so want to be when exporting more than 1800w to the grid turn on the switch for the HWS. had a delay of 5 seconds as well.

so far tried using the editor and its come out with the following:

- id: '1707530302402'
  alias: Shed HWS from solar
  description: ''
  - platform: numeric_state
    - sensor.barnett_site_power
      hours: 0
      minutes: 0
      seconds: 5
    below: -1800
  condition: []
  - service: switch.turn_on
    metadata: {}
    data: {}
      entity_id: switch.1001e2ad9f
  mode: single

seems to work only when i run it in settings menu.

how would i go about having this constantly checking state of solar export?
really would like to have it only on when more than 1800w exporting and if it drops below that, then turn it off as well.

thanks in advance/