{ config, ... }: 
let
  unstable = import
      (builtins.fetchTarball https://github.com/nixos/nixpkgs/tarball/nixpkgs-unstable)
      # reuse the current configuration
      { config = config.nixpkgs.config; };
in {
  services.home-assistant.customComponents = with unstable.home-assistant-custom-components; [
    epex_spot
  ];

  services.home-assistant.config = {
    sensor = [
      {
        platform = "template";
        sensors = {
          electricity_price = {
            friendly_name = "Current Price of electricity";
            unit_of_measurement = "EUR/kWh";
            value_template = ''
              {{ ((states('sensor.epex_spot_data_price') | float ) + (0.0149 + 0.074 + 0.007 + 0.0074 + 0.0006)) | float }}
            '';
            entity_id = [
              "sensor.epex_spot_data_price"
              "sensor.time"
            ];
          };
        };
      }
    ];
  };
}