Add Nord Pool integration (#35625)

Co-authored-by: c0ffeeca7 <38767475+c0ffeeca7@users.noreply.github.com>

source/_integrations/nordpool.markdown

@@ -0,0 +1,95 @@
+---
+title: Nord Pool
+description: Instructions on how to integrate with the Nord Pool Energy market prices.
+ha_category:
+  - Energy
+  - Finance
+  - Sensor
+ha_release: 2024.12
+ha_iot_class: Cloud Polling
+ha_config_flow: true
+ha_codeowners:
+  - '@gjohansson-ST'
+ha_domain: nordpool
+ha_platforms:
+  - sensor
+ha_integration_type: integration
+---
+
+The **Nord Pool** {% term integration %} integrates [Nord Pool Group](https://www.nordpoolgroup.com/) energy prices into Home Assistant.
+
+The {% term integration %} provides the public market prices displayed on the [Nord Pool Auction page](https://data.nordpoolgroup.com/auction/day-ahead/prices).
+
+{% include integrations/config_flow.md %}
+
+{% tip %}
+Only a single configuration entry is supported. When setting up the integration, ensure you select all the areas of interest.
+
+EUR is the base currency for market prices. If you choose another currency, you can find the conversion rate in the `Exchange rate` sensor.
+All prices are displayed as `selected_currency/kWh`.
+{% endtip %}
+
+{% configuration_basic %}
+Areas:
+  description: Select one or multiple market areas to create sensors for.
+Currency:
+  description: Currency to display prices in. EUR is the base currency in Nord Pool prices.
+{% endconfiguration_basic %}
+
+## Sensors
+
+Each market area will create a device which has the following sensors:
+
+### Main sensors
+
+- Current price for the selected area
+- Previous price for the selected area
+- Next price for the selected area
+
+These sensors can be used to calculate your current energy cost, or to help decide whether to charge the battery now or in an hour, etc.
+
+### Block price sensors
+
+- Block average
+- Block minimum
+- Block maximum
+- Block start time
+- Block end time
+
+These sensors show the minimum/maximum and average during certain blocks of the day. More known as off-peak (typically lower price) or peak hours (typically higher price).
+The block price sensors are not enabled by default.
+
+### Daily average
+
+- Daily average
+
+The daily average sensor is not enabled by default.
+
+### Diagnostic sensors
+
+- Last updated - indicates when the market price was last updated.
+- Currency - The selected currency.
+- Exchange rate - EUR is the base currency so will show the exchange rate used on the market place.
+
+The `Exchange rate` sensor is not enabled by default.
+
+## Example
+
+A simple template sensor to add VAT and a fixed cost from an `input_number` entity
+
+{% raw %}
+
+```yaml
+template:
+  - sensor:
+      - name: "Full SE3 current price"
+        unit_of_measurement: "SEK/kWh"
+        state_class: measurement
+        state: >
+          {% set cost = states('sensor.nord pool_se3_current_price') | float(0) %}
+          {% set add_cost = states('input_number.add_fixed_cost') | float(0) %}
+          # Add fixed cost to the spot price and add VAT (25%)
+          {{ ((cost + add_cost) * 1.25) | round(2, default=0) }}
+```
+
+{% endraw %}