MISO, which operates the power grid for much of central North America, has a public API that you can use to access real-time production data. You can turn this into a Home Assistant sensor by adding the following code to your configuration.yaml:

 

rest:
  - resource: 'https://api.misoenergy.org/MISORTWDDataBroker/DataBrokerServices.asmx?messageType=getfuelmix&returnType=json'
    scan_interval: 300
    sensor:
     - name: "Total grid power"
       value_template: "{{ value_json.TotalMW|int }}"
       device_class: power
       unit_of_measurement: "MW"
       icon: mdi:transmission-tower
     - name: "Grid coal"
       value_template: "{{ value_json.Fuel.Type.0.ACT|int }}"
       device_class: power
       unit_of_measurement: "MW"
       icon: mdi:factory
     - name: "Grid gas"
       value_template: "{{ value_json.Fuel.Type.1.ACT|int }}"
       device_class: power
       unit_of_measurement: "MW"
       icon: mdi:gas-burner
     - name: "Grid nuclear"
       value_template: "{{ value_json.Fuel.Type.2.ACT|int }}"
       device_class: power
       unit_of_measurement: "MW"
       icon: mdi:atom
     - name: "Grid wind"
       value_template: "{{ value_json.Fuel.Type.3.ACT|int }}"
       device_class: power
       unit_of_measurement: "MW"
       icon: mdi:wind-power
     - name: "Grid solar"
       value_template: "{{ value_json.Fuel.Type.4.ACT|int }}"
       device_class: power
       unit_of_measurement: "MW"
       icon: mdi:solar-power
     - name: "Grid other"
       value_template: "{{ value_json.Fuel.Type.5.ACT|int }}"
       device_class: power
       unit_of_measurement: "MW"
       icon: mdi:hydro-power

I don't drive much, so unless I have a big trip coming up, I rarely need a full battery. I want to turn the tap on when the electricity is clean, and off again when it's dirty. After collecting data for a while, I decided on cutoffs for how much coal power is too much (or how much wind is enough) and created automations to switch on/off the EVSE (which, in my case, is just a smart plug connected to the wall outlet that the charger's plugged into). I haven't figured out how to "set and forget" this one because of all the seasonal variation in power generation, but there could be a role for the Statistics integration here (for example, a script to detect when coal power generation is in the 10th percentile for a rolling 30-day window).

 

 

 

alias: Turn on EVSE when grid coal usage is low
description: ""
trigger:
  - platform: numeric_state
    entity_id: sensor.grid_coal
    below: 19999.9
condition:
  - condition: numeric_state
    entity_id: sensor.grid_wind
    above: 10000
action:
  - type: turn_on
    device_id: bd7c040ad491346705181910a569143d
    entity_id: switch.evse
    domain: switch
mode: single

alias: Turn off EVSE when coal usage is high
description: ""
trigger:
  - platform: numeric_state
    entity_id: sensor.grid_coal
    above: 24999.6
  - platform: numeric_state
    entity_id: sensor.grid_wind
    below: 8000
condition: []
action:
  - type: turn_off
    device_id: bd7c040ad491346705181910a569143d
    entity_id: switch.evse
    domain: switch
mode: single