add power tariff to price api docs

Author: davmoz

docs/developer/price-api.md

@@ -6,7 +6,24 @@ pagination_prev: null
 
 # Price API Developer Guide
 
-## Overview
+* [Price API Developer Guide](#price-api-developer-guide)
+   * [Overview](#overview)
+   * [Base URL](#base-url)
+   * [Endpoints](#endpoints)
+      * [Get Electricity Prices](#get-electricity-prices)
+         * [Default Provider](#default-provider)
+         * [Specific Provider](#specific-provider)
+      * [List Supported Areas](#list-supported-areas)
+      * [List Available Providers](#list-available-providers)
+      * [Power Tariffs](#power-tariffs)
+         * [List Power Tariff Providers](#list-power-tariff-providers)
+         * [Get Tariff Information](#get-tariff-information)
+         * [Get Pricing Rules](#get-pricing-rules)
+         * [Calculate Power Price](#calculate-power-price)
+      * [Health Check](#health-check)
+   * [Supported Areas](#supported-areas)
+   * [Error Responses](#error-responses)
+   * [Data Availability](#data-availability)
 
 REST API for accessing electricity prices from multiple providers. Returns today's prices and day-ahead prices (available after 11:00 UTC) in either raw XML format or unified JSON format.
 
@@ -121,6 +138,121 @@ GET /price/providers
 }
 ```
 
+### Power Tariffs
+
+#### List Power Tariff Providers
+
+```http
+GET /price/power-tariff/providers
+```
+
+**Response:**
+
+```json
+{
+  "supported_providers": [
+    {
+      "provider": "ellevio",
+      "provider_display_name": "Ellevio"
+    },
+    {
+      "provider": "goteborg_energi",
+      "provider_display_name": "Göteborg Energi"
+    }
+  ],
+  "total_count": 2
+}
+```
+
+#### Get Tariff Information
+
+```http
+GET /price/power-tariff/{provider}
+```
+
+**Parameters:**
+
+- `provider` (required): Provider identifier (e.g., `ellevio`, `goteborg_energi`)
+
+#### Get Pricing Rules
+
+```http
+GET /price/power-tariff/{provider}/rules
+```
+
+Returns detailed pricing rules including time-based pricing and peak calculations.
+
+**Response:**
+
+```json
+{
+  "provider": "Göteborg Energi",
+  "country": "Sweden",
+  "currency": "SEK",
+  "fuse_sizes": ["16A", "20A", "25A", "35A", "50A", "63A"],
+  "pricing_rules": {
+    "winter_high": {
+      "description": "High price during winter weekdays",
+      "season": {"start_month": 11, "end_month": 3},
+      "time_range": {"start": "07:00", "end": "20:00"},
+      "days": "weekdays_non_holidays",
+      "price_per_kw": 132
+    },
+    "summer_all": {
+      "description": "Low price all day during summer",
+      "season": {"start_month": 4, "end_month": 10},
+      "time_range": {"start": "00:00", "end": "23:59"},
+      "days": "all_days",
+      "price_per_kw": 0
+    }
+  },
+  "num_peaks": 3,
+  "holidays": ["2025-01-01", "2025-01-06", "..."],
+  "note": "Price varies by time of day and season. Uses winter time (CET) all year. Cost based on average of three highest peaks."
+}
+```
+
+#### Calculate Power Price
+
+```http
+GET /price/power-tariff/{provider}/calculate?timestamp={iso_datetime}&fuse_size={size}
+```
+
+Calculate power price for a specific timestamp and fuse size.
+
+**Parameters:**
+
+- `provider` (required): Provider identifier
+- `timestamp` (required): ISO datetime (e.g., `2025-01-15T10:30:00`)
+- `fuse_size` (optional): Fuse size (e.g., `16A`, `20A`)
+
+**Example:**
+
+```bash
+curl "https://mainnet.srcful.dev/price/power-tariff/goteborg_energi/calculate?timestamp=2025-04-30T23:30:00&fuse_size=16A"
+```
+
+**Response:**
+
+```json
+{
+  "provider": "Göteborg Energi",
+  "timestamp": "2025-04-30T23:30:00",
+  "currency": "SEK",
+  "fuse_size": "16A",
+  "applied_rules": [
+    {
+      "rule": "summer_all",
+      "description": "Low price all day during summer",
+      "price": 0
+    }
+  ],
+  "base_price_per_kw": 132,
+  "final_price_per_kw": 0,
+  "multiplier": 0
+}
+```
+
 ### Health Check
 
 ```http