fix(ElecPriceEnergyCharts): get history series, update docs (#606)

Signed-off-by: redmoon2711 <redmoon2711@gmx.de>

docs/akkudoktoreos/prediction.md

@@ -136,11 +136,21 @@ option are added.
 
 ### ElecPriceEnergyCharts Provider
 
-The `ElecPriceEnergyCharts` provider retrieves electricity prices directly from **Energy-Charts.info**,
+The `ElecPriceEnergyCharts` provider retrieves day-ahead electricity market prices from
-which supplies price data for the next 24 hours. For periods beyond 24 hours, the provider generates
+[Energy-Charts.info](https://www.Energy-Charts.info). It supports both short-term and extended forecasting by combining
-prices by extrapolating historical price data combined with the most recent actual prices obtained
+real-time market data with historical price trends.
-from Energy-Charts.info. Electricity price charges specified in the `charges_kwh` configuration option
+
-are included in the calculation as `(market price + charges_kwh) * 1.19 VAT`.
+- For the next 24 hours, market prices are fetched directly from Energy-Charts.info.
+- For periods beyond 24 hours, prices are estimated using extrapolation based on historical data and the latest
+  available market values.
+
+Charges and VAT
+
+- If `charges_kwh` configuration option is greater than 0, the electricity price is calculated as:
+  `(market price + charges_kwh) * 1.19 VAT` (including 19% VAT).
+- If `charges_kwh` is set to 0, the electricity price is simply: `market_price` (no VAT applied).
+
+**Note:** For the most accurate forecasts, it is recommended to set the `historic_hours` parameter to 840.
 
 ### ElecPriceImport Provider
 

src/akkudoktoreos/prediction/elecpriceenergycharts.py

@@ -177,18 +177,12 @@ class ElecPriceEnergyCharts(ElecPriceProvider):
         # Determine if update is needed and how many days
         past_days = 35
         if self.highest_orig_datetime:
-            # Try to get lowest datetime in history
+            history_series = self.key_to_series(
-            try:
+                key="elecprice_marketprice_wh", start_datetime=self.start_datetime
-                history = self.key_to_array(
-                    key="elecprice_marketprice_wh",
-                    start_datetime=self.start_datetime,
-                    fill_method="linear",
             )
-                # If start_datetime lower then history
+            # If history lower, then start_datetime
-                if history.index.min() <= self.start_datetime:
+            if history_series.index.min() <= self.start_datetime:
-                    past_days = 1
+                past_days = 0
-            except AttributeError as e:
-                logger.error(f"Energy-Charts no Index in history: {e}")
 
             needs_update = end > self.highest_orig_datetime
         else:
@@ -196,9 +190,9 @@ class ElecPriceEnergyCharts(ElecPriceProvider):
 
         if needs_update:
             logger.info(
-                f"Update ElecPriceEnergyCharts is needed, last update:{self.highest_orig_datetime}"
+                f"Update ElecPriceEnergyCharts is needed, last in history: {self.highest_orig_datetime}"
             )
-            # Set Start_date try to take data from 5 weeks back for prediction
+            # Set start_date try to take data from 5 weeks back for prediction
             start_date = to_datetime(
                 self.start_datetime - to_duration(f"{past_days} days"), as_string="YYYY-MM-DD"
             )
@@ -213,7 +207,7 @@ class ElecPriceEnergyCharts(ElecPriceProvider):
             self.key_from_series("elecprice_marketprice_wh", series_data)
         else:
             logger.info(
-                f"No update ElecPriceEnergyCharts is needed last update:{self.highest_orig_datetime}"
+                f"No Update ElecPriceEnergyCharts is needed, last in history: {self.highest_orig_datetime}"
             )
 
         # Generate history array for prediction