many changes and more modularizing

hosts/fw-new/modules/home-assistant/electricity.nix

@@ -0,0 +1,28 @@
+{ 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') | int ) / 1000) + (0.0149 + 0.053 + 0.00866)) | float }}
+            '';
+          };
+        };
+      }
+    ];
+  };
+}