diff --git a/custom_components/tibber_prices/__init__.py b/custom_components/tibber_prices/__init__.py
index 9f43185..d9dd3d8 100644
--- a/custom_components/tibber_prices/__init__.py
+++ b/custom_components/tibber_prices/__init__.py
@@ -11,8 +11,9 @@ from typing import TYPE_CHECKING, Any
 
 import voluptuous as vol
 
-from homeassistant.config_entries import ConfigEntryState
+from homeassistant.config_entries import ConfigEntry, ConfigEntryState
 from homeassistant.const import CONF_ACCESS_TOKEN, Platform
+from homeassistant.exceptions import ConfigEntryAuthFailed
 from homeassistant.helpers.aiohttp_client import async_get_clientsession
 from homeassistant.helpers.storage import Store
 from homeassistant.loader import async_get_loaded_integration
@@ -96,6 +97,43 @@ async def async_setup(hass: HomeAssistant, config: dict[str, Any]) -> bool:
     return True
 
 
+def _get_access_token(hass: HomeAssistant, entry: ConfigEntry) -> str:
+    """
+    Get access token from entry or parent entry.
+
+    For parent entries, the token is stored in entry.data.
+    For subentries, we need to find the parent entry and get its token.
+
+    Args:
+        hass: HomeAssistant instance
+        entry: Config entry (parent or subentry)
+
+    Returns:
+        Access token string
+
+    Raises:
+        ConfigEntryAuthFailed: If no access token found
+
+    """
+    # Try to get token from this entry (works for parent)
+    if CONF_ACCESS_TOKEN in entry.data:
+        return entry.data[CONF_ACCESS_TOKEN]
+
+    # This is a subentry, find parent entry
+    # Parent entry is the one without subentries in its data structure
+    # and has the same domain
+    for potential_parent in hass.config_entries.async_entries(DOMAIN):
+        # Parent has ACCESS_TOKEN and is not the current entry
+        if potential_parent.entry_id != entry.entry_id and CONF_ACCESS_TOKEN in potential_parent.data:
+            # Check if this entry is actually a subentry of this parent
+            # (HA Core manages this relationship internally)
+            return potential_parent.data[CONF_ACCESS_TOKEN]
+
+    # No token found anywhere
+    msg = f"No access token found for entry {entry.entry_id}"
+    raise ConfigEntryAuthFailed(msg)
+
+
 # https://developers.home-assistant.io/docs/config_entries_index/#setting-up-an-entry
 async def async_setup_entry(
     hass: HomeAssistant,
@@ -117,10 +155,20 @@ async def async_setup_entry(
 
     integration = async_get_loaded_integration(hass, entry.domain)
 
+    # Get access token (from this entry if parent, from parent if subentry)
+    access_token = _get_access_token(hass, entry)
+
+    # Create API client
+    api_client = TibberPricesApiClient(
+        access_token=access_token,
+        session=async_get_clientsession(hass),
+        version=str(integration.version) if integration.version else "unknown",
+    )
+
     coordinator = TibberPricesDataUpdateCoordinator(
         hass=hass,
         config_entry=entry,
-        version=str(integration.version) if integration.version else "unknown",
+        api_client=api_client,
     )
 
     # CRITICAL: Load cache BEFORE first refresh to ensure user_data is available
@@ -129,11 +177,7 @@ async def async_setup_entry(
     await coordinator.load_cache()
 
     entry.runtime_data = TibberPricesData(
-        client=TibberPricesApiClient(
-            access_token=entry.data[CONF_ACCESS_TOKEN],
-            session=async_get_clientsession(hass),
-            version=str(integration.version) if integration.version else "unknown",
-        ),
+        client=api_client,
         integration=integration,
         coordinator=coordinator,
     )
diff --git a/custom_components/tibber_prices/api/client.py b/custom_components/tibber_prices/api/client.py
index c482f01..0d27f31 100644
--- a/custom_components/tibber_prices/api/client.py
+++ b/custom_components/tibber_prices/api/client.py
@@ -136,21 +136,21 @@ class TibberPricesApiClient:
             query_type=TibberPricesQueryType.USER,
         )
 
-    async def async_get_price_info(self, home_ids: set[str], user_data: dict[str, Any]) -> dict:
+    async def async_get_price_info(self, home_id: str, user_data: dict[str, Any]) -> dict:
         """
-        Get price info for specific homes using GraphQL aliases.
+        Get price info for a single home.
 
-        Uses timezone-aware cursor calculation per home based on the home's actual timezone
+        Uses timezone-aware cursor calculation based on the home's actual timezone
         from Tibber API (not HA system timezone). This ensures correct "day before yesterday
         midnight" calculation for homes in different timezones.
 
         Args:
-            home_ids: Set of home IDs to fetch price data for.
+            home_id: Home ID to fetch price data for.
             user_data: User data dict containing home metadata (including timezone).
                       REQUIRED - must be fetched before calling this method.
 
         Returns:
-            Dict with "homes" key containing home_id -> price_data mapping.
+            Dict with "home_id", "price_info", and other home data.
 
         Raises:
             TibberPricesApiClientError: If TimeService not initialized or user_data missing.
@@ -164,26 +164,23 @@ class TibberPricesApiClient:
             msg = "User data required for timezone-aware price fetching - fetch user data first"
             raise TibberPricesApiClientError(msg)
 
-        if not home_ids:
-            return {"homes": {}}
+        if not home_id:
+            msg = "Home ID is required"
+            raise TibberPricesApiClientError(msg)
 
         # Build home_id -> timezone mapping from user_data
         home_timezones = self._extract_home_timezones(user_data)
 
-        # Build query with aliases for each home
-        # Each home gets its own cursor based on its timezone
-        home_queries = []
-        for idx, home_id in enumerate(sorted(home_ids)):
-            alias = f"home{idx}"
+        # Get timezone for this home (fallback to HA system timezone)
+        home_tz = home_timezones.get(home_id)
 
-            # Get timezone for this home (fallback to HA system timezone)
-            home_tz = home_timezones.get(home_id)
+        # Calculate cursor: day before yesterday midnight in home's timezone
+        cursor = self._calculate_cursor_for_home(home_tz)
 
-            # Calculate cursor: day before yesterday midnight in home's timezone
-            cursor = self._calculate_cursor_for_home(home_tz)
-
-            home_query = f"""
-                {alias}: home(id: "{home_id}") {{
+        # Simple single-home query (no alias needed)
+        query = f"""
+            {{viewer{{
+                home(id: "{home_id}") {{
                     id
                     currentSubscription {{
                         priceInfoRange(resolution:QUARTER_HOURLY, first:192, after: "{cursor}") {{
@@ -198,42 +195,38 @@ class TibberPricesApiClient:
                         }}
                     }}
                 }}
-            """
-            home_queries.append(home_query)
+            }}}}
+        """
 
-        query = "{viewer{" + "".join(home_queries) + "}}"
-
-        _LOGGER.debug("Fetching price info for %d specific home(s)", len(home_ids))
+        _LOGGER.debug("Fetching price info for home %s", home_id)
 
         data = await self._api_wrapper(
             data={"query": query},
             query_type=TibberPricesQueryType.PRICE_INFO,
         )
 
-        # Parse aliased response
+        # Parse response
         viewer = data.get("viewer", {})
-        homes_data = {}
+        home = viewer.get("home")
 
-        for idx, home_id in enumerate(sorted(home_ids)):
-            alias = f"home{idx}"
-            home = viewer.get(alias)
+        if not home:
+            msg = f"Home {home_id} not found in API response"
+            _LOGGER.warning(msg)
+            return {"home_id": home_id, "price_info": []}
 
-            if not home:
-                _LOGGER.debug("Home %s not found in API response", home_id)
-                homes_data[home_id] = {}
-                continue
+        if "currentSubscription" in home and home["currentSubscription"] is not None:
+            price_info = flatten_price_info(home["currentSubscription"])
+        else:
+            _LOGGER.warning(
+                "Home %s has no active subscription - price data will be unavailable",
+                home_id,
+            )
+            price_info = []
 
-            if "currentSubscription" in home and home["currentSubscription"] is not None:
-                homes_data[home_id] = flatten_price_info(home["currentSubscription"])
-            else:
-                _LOGGER.debug(
-                    "Home %s has no active subscription - price data will be unavailable",
-                    home_id,
-                )
-                homes_data[home_id] = {}
-
-        data["homes"] = homes_data
-        return data
+        return {
+            "home_id": home_id,
+            "price_info": price_info,
+        }
 
     def _extract_home_timezones(self, user_data: dict[str, Any]) -> dict[str, str]:
         """
diff --git a/custom_components/tibber_prices/api/helpers.py b/custom_components/tibber_prices/api/helpers.py
index 826a7cc..8b461b7 100644
--- a/custom_components/tibber_prices/api/helpers.py
+++ b/custom_components/tibber_prices/api/helpers.py
@@ -145,27 +145,21 @@ def is_data_empty(data: dict, query_type: str) -> bool:
             )
 
         elif query_type == "price_info":
-            # Check for home aliases (home0, home1, etc.)
+            # Check for single home data (viewer.home)
             viewer = data.get("viewer", {})
-            home_aliases = [key for key in viewer if key.startswith("home") and key[4:].isdigit()]
+            home_data = viewer.get("home")
 
-            if not home_aliases:
-                _LOGGER.debug("No home aliases found in price_info response")
+            if not home_data:
+                _LOGGER.debug("No home data found in price_info response")
                 is_empty = True
             else:
-                # Check first home for valid data
-                _LOGGER.debug("Checking price_info with %d home(s)", len(home_aliases))
-                first_home = viewer.get(home_aliases[0])
+                _LOGGER.debug("Checking price_info for single home")
 
-                if (
-                    not first_home
-                    or "currentSubscription" not in first_home
-                    or first_home["currentSubscription"] is None
-                ):
-                    _LOGGER.debug("Missing currentSubscription in first home")
+                if not home_data or "currentSubscription" not in home_data or home_data["currentSubscription"] is None:
+                    _LOGGER.debug("Missing currentSubscription in home")
                     is_empty = True
                 else:
-                    subscription = first_home["currentSubscription"]
+                    subscription = home_data["currentSubscription"]
 
                     # Check priceInfoRange (96 quarter-hourly intervals)
                     has_yesterday = (
diff --git a/custom_components/tibber_prices/binary_sensor/attributes.py b/custom_components/tibber_prices/binary_sensor/attributes.py
index d4eb769..576081b 100644
--- a/custom_components/tibber_prices/binary_sensor/attributes.py
+++ b/custom_components/tibber_prices/binary_sensor/attributes.py
@@ -90,7 +90,7 @@ def get_price_intervals_attributes(
         return build_no_periods_result(time=time)
 
     # Get precomputed period summaries from coordinator
-    periods_data = coordinator_data.get("periods", {})
+    periods_data = coordinator_data.get("pricePeriods", {})
     period_type = "peak_price" if reverse_sort else "best_price"
     period_data = periods_data.get(period_type)
 
diff --git a/custom_components/tibber_prices/coordinator/core.py b/custom_components/tibber_prices/coordinator/core.py
index 428b631..f4df201 100644
--- a/custom_components/tibber_prices/coordinator/core.py
+++ b/custom_components/tibber_prices/coordinator/core.py
@@ -6,11 +6,9 @@ import logging
 from datetime import timedelta
 from typing import TYPE_CHECKING, Any
 
-from homeassistant.const import CONF_ACCESS_TOKEN
 from homeassistant.core import CALLBACK_TYPE, HomeAssistant, callback
-from homeassistant.helpers import aiohttp_client
 from homeassistant.helpers.storage import Store
-from homeassistant.helpers.update_coordinator import DataUpdateCoordinator, UpdateFailed
+from homeassistant.helpers.update_coordinator import DataUpdateCoordinator
 
 if TYPE_CHECKING:
     from collections.abc import Callable
@@ -164,7 +162,7 @@ class TibberPricesDataUpdateCoordinator(DataUpdateCoordinator[dict[str, Any]]):
         self,
         hass: HomeAssistant,
         config_entry: ConfigEntry,
-        version: str,
+        api_client: TibberPricesApiClient,
     ) -> None:
         """Initialize the coordinator."""
         super().__init__(
@@ -175,11 +173,14 @@ class TibberPricesDataUpdateCoordinator(DataUpdateCoordinator[dict[str, Any]]):
         )
 
         self.config_entry = config_entry
-        self.api = TibberPricesApiClient(
-            access_token=config_entry.data[CONF_ACCESS_TOKEN],
-            session=aiohttp_client.async_get_clientsession(hass),
-            version=version,
-        )
+
+        # Get home_id from config entry
+        self._home_id = config_entry.data.get("home_id", "")
+        if not self._home_id:
+            _LOGGER.error("No home_id found in config entry %s", config_entry.entry_id)
+
+        # Use the API client from runtime_data (created in __init__.py with proper TOKEN handling)
+        self.api = api_client
 
         # Storage for persistence
         storage_key = f"{DOMAIN}.{config_entry.entry_id}"
@@ -188,8 +189,8 @@ class TibberPricesDataUpdateCoordinator(DataUpdateCoordinator[dict[str, Any]]):
         # Log prefix for identifying this coordinator instance
         self._log_prefix = f"[{config_entry.title}]"
 
-        # Track if this is the main entry (first one created)
-        self._is_main_entry = not self._has_existing_main_coordinator()
+        # Note: In the new architecture, all coordinators (parent + subentries) fetch their own data
+        # No distinction between "main" and "sub" coordinators anymore
 
         # Initialize time service (single source of truth for all time operations)
         self.time = TibberPricesTimeService()
@@ -440,11 +441,7 @@ class TibberPricesDataUpdateCoordinator(DataUpdateCoordinator[dict[str, Any]]):
         # Just update coordinator's data to trigger entity updates.
         if self.data and self._cached_price_data:
             # Re-transform data to ensure enrichment is refreshed
-            if self.is_main_entry():
-                self.data = self._transform_data_for_main_entry(self._cached_price_data)
-            else:
-                # For subentry, get fresh data from main coordinator
-                pass
+            self.data = self._transform_data(self._cached_price_data)
 
             # CRITICAL: Update _last_price_update to current time after midnight
             # This prevents cache_validity from showing "date_mismatch" after midnight
@@ -517,18 +514,6 @@ class TibberPricesDataUpdateCoordinator(DataUpdateCoordinator[dict[str, Any]]):
             # Log but don't raise - shutdown should complete even if cache save fails
             self._log("error", "Failed to save cache during shutdown: %s", err)
 
-    def _has_existing_main_coordinator(self) -> bool:
-        """Check if there's already a main coordinator in hass.data."""
-        domain_data = self.hass.data.get(DOMAIN, {})
-        return any(
-            isinstance(coordinator, TibberPricesDataUpdateCoordinator) and coordinator.is_main_entry()
-            for coordinator in domain_data.values()
-        )
-
-    def is_main_entry(self) -> bool:
-        """Return True if this is the main entry that fetches data for all homes."""
-        return self._is_main_entry
-
     async def _async_update_data(self) -> dict[str, Any]:
         """
         Fetch data from Tibber API (called by DataUpdateCoordinator timer).
@@ -589,46 +574,37 @@ class TibberPricesDataUpdateCoordinator(DataUpdateCoordinator[dict[str, Any]]):
                 return self.data
 
         try:
-            if self.is_main_entry():
-                # Reset API call counter if day changed
-                current_date = current_time.date()
-                if self._last_api_call_date != current_date:
-                    self._api_calls_today = 0
-                    self._last_api_call_date = current_date
+            # Reset API call counter if day changed
+            current_date = current_time.date()
+            if self._last_api_call_date != current_date:
+                self._api_calls_today = 0
+                self._last_api_call_date = current_date
 
-                # Main entry fetches data for all homes
-                configured_home_ids = self._get_configured_home_ids()
+            # Track last_price_update timestamp before fetch to detect if data actually changed
+            old_price_update = self._last_price_update
 
-                # Track last_price_update timestamp before fetch to detect if data actually changed
-                old_price_update = self._last_price_update
+            result = await self._data_fetcher.handle_main_entry_update(
+                current_time,
+                self._home_id,
+                self._transform_data,
+            )
 
-                result = await self._data_fetcher.handle_main_entry_update(
-                    current_time,
-                    configured_home_ids,
-                    self._transform_data_for_main_entry,
-                )
-
-                # CRITICAL: Sync cached data after API call
-                # handle_main_entry_update() updates data_fetcher's cache, we need to sync:
-                # 1. cached_user_data (for new integrations, may be fetched via update_user_data_if_needed())
-                # 2. cached_price_data (CRITICAL: contains tomorrow data, needed for _needs_tomorrow_data())
-                # 3. _last_price_update (for lifecycle tracking: cache age, fresh state detection)
-                self._cached_user_data = self._data_fetcher.cached_user_data
-                self._cached_price_data = self._data_fetcher.cached_price_data
-                self._last_price_update = self._data_fetcher._last_price_update  # noqa: SLF001 - Sync for lifecycle tracking
-
-                # Update lifecycle tracking only if we fetched NEW data (timestamp changed)
-                # This prevents recorder spam from state changes when returning cached data
-                if self._last_price_update != old_price_update:
-                    self._api_calls_today += 1
-                    self._lifecycle_state = "fresh"  # Data just fetched
-                    # No separate lifecycle notification needed - normal async_update_listeners()
-                    # will trigger all entities (including lifecycle sensor) after this return
-
-                return result
-            # Subentries get data from main coordinator (no lifecycle tracking - they don't fetch)
-            return await self._handle_subentry_update()
+            # CRITICAL: Sync cached data after API call
+            # handle_main_entry_update() updates data_fetcher's cache, we need to sync:
+            # 1. cached_user_data (for new integrations, may be fetched via update_user_data_if_needed())
+            # 2. cached_price_data (CRITICAL: contains tomorrow data, needed for _needs_tomorrow_data())
+            # 3. _last_price_update (for lifecycle tracking: cache age, fresh state detection)
+            self._cached_user_data = self._data_fetcher.cached_user_data
+            self._cached_price_data = self._data_fetcher.cached_price_data
+            self._last_price_update = self._data_fetcher._last_price_update  # noqa: SLF001 - Sync for lifecycle tracking
 
+            # Update lifecycle tracking only if we fetched NEW data (timestamp changed)
+            # This prevents recorder spam from state changes when returning cached data
+            if self._last_price_update != old_price_update:
+                self._api_calls_today += 1
+                self._lifecycle_state = "fresh"  # Data just fetched
+                # No separate lifecycle notification needed - normal async_update_listeners()
+                # will trigger all entities (including lifecycle sensor) after this return
         except (
             TibberPricesApiClientAuthenticationError,
             TibberPricesApiClientCommunicationError,
@@ -641,53 +617,10 @@ class TibberPricesDataUpdateCoordinator(DataUpdateCoordinator[dict[str, Any]]):
             # which triggers normal async_update_listeners()
             return await self._data_fetcher.handle_api_error(
                 err,
-                self._transform_data_for_main_entry,
+                self._transform_data,
             )
-
-    async def _handle_subentry_update(self) -> dict[str, Any]:
-        """Handle update for subentry - get data from main coordinator."""
-        main_data = await self._get_data_from_main_coordinator()
-        return self._transform_data_for_subentry(main_data)
-
-    async def _get_data_from_main_coordinator(self) -> dict[str, Any]:
-        """Get data from the main coordinator (subentries only)."""
-        # Find the main coordinator
-        main_coordinator = self._find_main_coordinator()
-        if not main_coordinator:
-            msg = "Main coordinator not found"
-            raise UpdateFailed(msg)
-
-        # Wait for main coordinator to have data
-        if main_coordinator.data is None:
-            main_coordinator.async_set_updated_data({})
-
-        # Return the main coordinator's data
-        return main_coordinator.data or {}
-
-    def _find_main_coordinator(self) -> TibberPricesDataUpdateCoordinator | None:
-        """Find the main coordinator that fetches data for all homes."""
-        domain_data = self.hass.data.get(DOMAIN, {})
-        for coordinator in domain_data.values():
-            if (
-                isinstance(coordinator, TibberPricesDataUpdateCoordinator)
-                and coordinator.is_main_entry()
-                and coordinator != self
-            ):
-                return coordinator
-        return None
-
-    def _get_configured_home_ids(self) -> set[str]:
-        """Get all home_ids that have active config entries (main + subentries)."""
-        home_ids = helpers.get_configured_home_ids(self.hass)
-
-        self._log(
-            "debug",
-            "Found %d configured home(s): %s",
-            len(home_ids),
-            ", ".join(sorted(home_ids)),
-        )
-
-        return home_ids
+        else:
+            return result
 
     async def load_cache(self) -> None:
         """Load cached data from storage."""
@@ -714,20 +647,20 @@ class TibberPricesDataUpdateCoordinator(DataUpdateCoordinator[dict[str, Any]]):
         """Store cache data."""
         await self._data_fetcher.store_cache(self._midnight_handler.last_check_time)
 
-    def _needs_tomorrow_data(self, tomorrow_date: date) -> bool:
+    def _needs_tomorrow_data(self) -> bool:
         """Check if tomorrow data is missing or invalid."""
-        return helpers.needs_tomorrow_data(self._cached_price_data, tomorrow_date)
+        return helpers.needs_tomorrow_data(self._cached_price_data)
 
-    def _has_valid_tomorrow_data(self, tomorrow_date: date) -> bool:
+    def _has_valid_tomorrow_data(self) -> bool:
         """Check if we have valid tomorrow data (inverse of _needs_tomorrow_data)."""
-        return not self._needs_tomorrow_data(tomorrow_date)
+        return not self._needs_tomorrow_data()
 
     @callback
     def _merge_cached_data(self) -> dict[str, Any]:
         """Merge cached data into the expected format for main entry."""
         if not self._cached_price_data:
             return {}
-        return self._transform_data_for_main_entry(self._cached_price_data)
+        return self._transform_data(self._cached_price_data)
 
     def _get_threshold_percentages(self) -> dict[str, int]:
         """Get threshold percentages from config options."""
@@ -737,31 +670,25 @@ class TibberPricesDataUpdateCoordinator(DataUpdateCoordinator[dict[str, Any]]):
         """Calculate periods (best price and peak price) for the given price info."""
         return self._period_calculator.calculate_periods_for_price_info(price_info)
 
-    def _transform_data_for_main_entry(self, raw_data: dict[str, Any]) -> dict[str, Any]:
+    def _transform_data(self, raw_data: dict[str, Any]) -> dict[str, Any]:
         """Transform raw data for main entry (aggregated view of all homes)."""
         # Delegate complete transformation to DataTransformer (enrichment + periods)
         # DataTransformer handles its own caching internally
-        return self._data_transformer.transform_data_for_main_entry(raw_data)
-
-    def _transform_data_for_subentry(self, main_data: dict[str, Any]) -> dict[str, Any]:
-        """Transform main coordinator data for subentry (home-specific view)."""
-        home_id = self.config_entry.data.get("home_id")
-        if not home_id:
-            return main_data
-
-        # Delegate complete transformation to DataTransformer (enrichment + periods)
-        # DataTransformer handles its own caching internally
-        return self._data_transformer.transform_data_for_subentry(main_data, home_id)
+        return self._data_transformer.transform_data(raw_data)
 
     # --- Methods expected by sensors and services ---
 
     def get_home_data(self, home_id: str) -> dict[str, Any] | None:
-        """Get data for a specific home."""
+        """Get data for a specific home (returns this coordinator's data if home_id matches)."""
         if not self.data:
             return None
 
-        homes_data = self.data.get("homes", {})
-        return homes_data.get(home_id)
+        # In new architecture, each coordinator manages one home only
+        # Return data only if requesting this coordinator's home
+        if home_id == self._home_id:
+            return self.data
+
+        return None
 
     def get_current_interval(self) -> dict[str, Any] | None:
         """Get the price data for the current interval."""
diff --git a/custom_components/tibber_prices/coordinator/data_transformation.py b/custom_components/tibber_prices/coordinator/data_transformation.py
index 9c674d9..9f5f6d4 100644
--- a/custom_components/tibber_prices/coordinator/data_transformation.py
+++ b/custom_components/tibber_prices/coordinator/data_transformation.py
@@ -155,8 +155,8 @@ class TibberPricesDataTransformer:
 
         return False
 
-    def transform_data_for_main_entry(self, raw_data: dict[str, Any]) -> dict[str, Any]:
-        """Transform raw data for main entry (aggregated view of all homes)."""
+    def transform_data(self, raw_data: dict[str, Any]) -> dict[str, Any]:
+        """Transform raw data for main entry (single home view)."""
         current_time = self.time.now()
         source_data_timestamp = raw_data.get("timestamp")
 
@@ -170,23 +170,23 @@ class TibberPricesDataTransformer:
 
         self._log("debug", "Transforming price data (enrichment + period calculation)")
 
-        # For main entry, we can show data from the first home as default
-        # or provide an aggregated view
-        homes_data = raw_data.get("homes", {})
-        if not homes_data:
+        # Extract data from single-home structure
+        home_id = raw_data.get("home_id", "")
+        all_intervals = raw_data.get("price_info", [])
+        currency = raw_data.get("currency", "EUR")
+
+        if not all_intervals:
             return {
                 "timestamp": raw_data.get("timestamp"),
-                "homes": {},
-                "priceInfo": {},
+                "home_id": home_id,
+                "priceInfo": [],
+                "pricePeriods": {
+                    "best_price": [],
+                    "peak_price": [],
+                },
+                "currency": currency,
             }
 
-        # Use the first home's data as the main entry's data
-        first_home_data = next(iter(homes_data.values()))
-        all_intervals = first_home_data.get("price_info", [])
-
-        # Extract currency from home_data (populated from user_data)
-        currency = first_home_data.get("currency", "EUR")
-
         # Enrich price info dynamically with calculated differences and rating levels
         # (Modifies all_intervals in-place, returns same list)
         thresholds = self.get_threshold_percentages()
@@ -199,74 +199,14 @@ class TibberPricesDataTransformer:
 
         # Store enriched intervals directly as priceInfo (flat list)
         transformed_data = {
-            "homes": homes_data,
+            "home_id": home_id,
             "priceInfo": enriched_intervals,
             "currency": currency,
         }
 
         # Calculate periods (best price and peak price)
         if "priceInfo" in transformed_data:
-            transformed_data["periods"] = self._calculate_periods_fn(transformed_data["priceInfo"])
-
-        # Cache the transformed data
-        self._cached_transformed_data = transformed_data
-        self._last_transformation_config = self._get_current_transformation_config()
-        self._last_midnight_check = current_time
-        self._last_source_data_timestamp = source_data_timestamp
-
-        return transformed_data
-
-    def transform_data_for_subentry(self, main_data: dict[str, Any], home_id: str) -> dict[str, Any]:
-        """Transform main coordinator data for subentry (home-specific view)."""
-        current_time = self.time.now()
-        source_data_timestamp = main_data.get("timestamp")
-
-        # Return cached transformed data if no retransformation needed
-        if (
-            not self._should_retransform_data(current_time, source_data_timestamp)
-            and self._cached_transformed_data is not None
-        ):
-            self._log("debug", "Using cached transformed data (no transformation needed)")
-            return self._cached_transformed_data
-
-        self._log("debug", "Transforming price data for home (enrichment + period calculation)")
-
-        if not home_id:
-            return main_data
-
-        homes_data = main_data.get("homes", {})
-        home_data = homes_data.get(home_id, {})
-
-        if not home_data:
-            return {
-                "timestamp": main_data.get("timestamp"),
-                "priceInfo": {},
-            }
-
-        all_intervals = home_data.get("price_info", [])
-
-        # Extract currency from home_data (populated from user_data)
-        currency = home_data.get("currency", "EUR")
-
-        # Enrich price info dynamically with calculated differences and rating levels
-        # (Modifies all_intervals in-place, returns same list)
-        thresholds = self.get_threshold_percentages()
-        enriched_intervals = enrich_price_info_with_differences(
-            all_intervals,
-            threshold_low=thresholds["low"],
-            threshold_high=thresholds["high"],
-            time=self.time,
-        )
-
-        # Store enriched intervals directly as priceInfo (flat list)
-        transformed_data = {
-            "priceInfo": enriched_intervals,
-            "currency": currency,
-        }
-
-        # Calculate periods (best price and peak price)
-        if "priceInfo" in transformed_data:
-            transformed_data["periods"] = self._calculate_periods_fn(transformed_data["priceInfo"])
+            transformed_data["pricePeriods"] = self._calculate_periods_fn(transformed_data["priceInfo"])
 
         # Cache the transformed data
         self._cached_transformed_data = transformed_data
diff --git a/custom_components/tibber_prices/coordinator/period_handlers/relaxation.py b/custom_components/tibber_prices/coordinator/period_handlers/relaxation.py
index f231abb..ec13a4f 100644
--- a/custom_components/tibber_prices/coordinator/period_handlers/relaxation.py
+++ b/custom_components/tibber_prices/coordinator/period_handlers/relaxation.py
@@ -145,7 +145,7 @@ def calculate_periods_with_relaxation(  # noqa: PLR0913, PLR0915 - Per-day relax
     max_relaxation_attempts: int,
     should_show_callback: Callable[[str | None], bool],
     time: TibberPricesTimeService,
-) -> tuple[dict[str, Any], dict[str, Any]]:
+) -> dict[str, Any]:
     """
     Calculate periods with optional per-day filter relaxation.
 
@@ -172,9 +172,10 @@ def calculate_periods_with_relaxation(  # noqa: PLR0913, PLR0915 - Per-day relax
         time: TibberPricesTimeService instance (required)
 
     Returns:
-        Tuple of (periods_result, relaxation_metadata):
-        - periods_result: Same format as calculate_periods() output, with periods from all days
-        - relaxation_metadata: Dict with relaxation information (aggregated across all days)
+        Dict with same format as calculate_periods() output:
+        - periods: List of period summaries
+        - metadata: Config and statistics (includes relaxation info)
+        - reference_data: Daily min/max/avg prices
 
     """
     # Import here to avoid circular dependency
@@ -244,11 +245,17 @@ def calculate_periods_with_relaxation(  # noqa: PLR0913, PLR0915 - Per-day relax
         _LOGGER.warning(
             "No price data available - cannot calculate periods",
         )
-        return {"periods": [], "metadata": {}, "reference_data": {}}, {
-            "relaxation_active": False,
-            "relaxation_attempted": False,
-            "min_periods_requested": min_periods if enable_relaxation else 0,
-            "periods_found": 0,
+        return {
+            "periods": [],
+            "metadata": {
+                "relaxation": {
+                    "relaxation_active": False,
+                    "relaxation_attempted": False,
+                    "min_periods_requested": min_periods if enable_relaxation else 0,
+                    "periods_found": 0,
+                },
+            },
+            "reference_data": {},
         }
 
     # Count available days for logging (today and future only)
@@ -345,7 +352,10 @@ def calculate_periods_with_relaxation(  # noqa: PLR0913, PLR0915 - Per-day relax
 
     total_periods = len(all_periods)
 
-    return final_result, {
+    # Add relaxation info to metadata
+    if "metadata" not in final_result:
+        final_result["metadata"] = {}
+    final_result["metadata"]["relaxation"] = {
         "relaxation_active": relaxation_was_needed,
         "relaxation_attempted": relaxation_was_needed,
         "min_periods_requested": min_periods,
@@ -356,6 +366,8 @@ def calculate_periods_with_relaxation(  # noqa: PLR0913, PLR0915 - Per-day relax
         "relaxation_incomplete": days_meeting_requirement < total_days,
     }
 
+    return final_result
+
 
 def relax_all_prices(  # noqa: PLR0913 - Comprehensive filter relaxation requires many parameters and statements
     all_prices: list[dict],
diff --git a/custom_components/tibber_prices/coordinator/periods.py b/custom_components/tibber_prices/coordinator/periods.py
index 5fc4807..c706f0e 100644
--- a/custom_components/tibber_prices/coordinator/periods.py
+++ b/custom_components/tibber_prices/coordinator/periods.py
@@ -637,7 +637,7 @@ class TibberPricesPeriodCalculator:
                 level_filter=max_level_best,
                 gap_count=gap_count_best,
             )
-            best_periods, best_relaxation = calculate_periods_with_relaxation(
+            best_periods = calculate_periods_with_relaxation(
                 all_prices,
                 config=best_period_config,
                 enable_relaxation=enable_relaxation_best,
@@ -654,9 +654,13 @@ class TibberPricesPeriodCalculator:
             best_periods = {
                 "periods": [],
                 "intervals": [],
-                "metadata": {"total_intervals": 0, "total_periods": 0, "config": {}},
+                "metadata": {
+                    "total_intervals": 0,
+                    "total_periods": 0,
+                    "config": {},
+                    "relaxation": {"relaxation_active": False, "relaxation_attempted": False},
+                },
             }
-            best_relaxation = {"relaxation_active": False, "relaxation_attempted": False}
 
         # Get relaxation configuration for peak price
         enable_relaxation_peak = self.config_entry.options.get(
@@ -705,7 +709,7 @@ class TibberPricesPeriodCalculator:
                 level_filter=min_level_peak,
                 gap_count=gap_count_peak,
             )
-            peak_periods, peak_relaxation = calculate_periods_with_relaxation(
+            peak_periods = calculate_periods_with_relaxation(
                 all_prices,
                 config=peak_period_config,
                 enable_relaxation=enable_relaxation_peak,
@@ -722,15 +726,17 @@ class TibberPricesPeriodCalculator:
             peak_periods = {
                 "periods": [],
                 "intervals": [],
-                "metadata": {"total_intervals": 0, "total_periods": 0, "config": {}},
+                "metadata": {
+                    "total_intervals": 0,
+                    "total_periods": 0,
+                    "config": {},
+                    "relaxation": {"relaxation_active": False, "relaxation_attempted": False},
+                },
             }
-            peak_relaxation = {"relaxation_active": False, "relaxation_attempted": False}
 
         result = {
             "best_price": best_periods,
-            "best_price_relaxation": best_relaxation,
             "peak_price": peak_periods,
-            "peak_price_relaxation": peak_relaxation,
         }
 
         # Cache the result
diff --git a/custom_components/tibber_prices/diagnostics.py b/custom_components/tibber_prices/diagnostics.py
index c178679..c5278b5 100644
--- a/custom_components/tibber_prices/diagnostics.py
+++ b/custom_components/tibber_prices/diagnostics.py
@@ -22,6 +22,9 @@ async def async_get_config_entry_diagnostics(
     """Return diagnostics for a config entry."""
     coordinator = entry.runtime_data.coordinator
 
+    # Get period metadata from coordinator data
+    price_periods = coordinator.data.get("pricePeriods", {}) if coordinator.data else {}
+
     return {
         "entry": {
             "entry_id": entry.entry_id,
@@ -30,16 +33,46 @@ async def async_get_config_entry_diagnostics(
             "domain": entry.domain,
             "title": entry.title,
             "state": str(entry.state),
+            "home_id": entry.data.get("home_id", ""),
         },
         "coordinator": {
             "last_update_success": coordinator.last_update_success,
             "update_interval": str(coordinator.update_interval),
-            "is_main_entry": coordinator.is_main_entry(),
             "data": coordinator.data,
             "update_timestamps": {
                 "price": coordinator._last_price_update.isoformat() if coordinator._last_price_update else None,  # noqa: SLF001
                 "user": coordinator._last_user_update.isoformat() if coordinator._last_user_update else None,  # noqa: SLF001
+                "last_coordinator_update": coordinator._last_coordinator_update.isoformat()  # noqa: SLF001
+                if coordinator._last_coordinator_update  # noqa: SLF001
+                else None,
             },
+            "lifecycle": {
+                "state": coordinator._lifecycle_state,  # noqa: SLF001
+                "is_fetching": coordinator._is_fetching,  # noqa: SLF001
+                "api_calls_today": coordinator._api_calls_today,  # noqa: SLF001
+                "last_api_call_date": coordinator._last_api_call_date.isoformat()  # noqa: SLF001
+                if coordinator._last_api_call_date  # noqa: SLF001
+                else None,
+            },
+        },
+        "periods": {
+            "best_price": {
+                "count": len(price_periods.get("best_price", {}).get("periods", [])),
+                "metadata": price_periods.get("best_price", {}).get("metadata", {}),
+            },
+            "peak_price": {
+                "count": len(price_periods.get("peak_price", {}).get("periods", [])),
+                "metadata": price_periods.get("peak_price", {}).get("metadata", {}),
+            },
+        },
+        "config": {
+            "options": dict(entry.options),
+        },
+        "cache_status": {
+            "user_data_cached": coordinator._cached_user_data is not None,  # noqa: SLF001
+            "price_data_cached": coordinator._cached_price_data is not None,  # noqa: SLF001
+            "transformer_cache_valid": coordinator._data_transformer._cached_transformed_data is not None,  # noqa: SLF001
+            "period_calculator_cache_valid": coordinator._period_calculator._cached_periods is not None,  # noqa: SLF001
         },
         "error": {
             "last_exception": str(coordinator.last_exception) if coordinator.last_exception else None,
diff --git a/custom_components/tibber_prices/sensor/calculators/timing.py b/custom_components/tibber_prices/sensor/calculators/timing.py
index 640b803..63c02ca 100644
--- a/custom_components/tibber_prices/sensor/calculators/timing.py
+++ b/custom_components/tibber_prices/sensor/calculators/timing.py
@@ -69,7 +69,7 @@ class TibberPricesTimingCalculator(TibberPricesBaseCalculator):
             return None
 
         # Get period data from coordinator
-        periods_data = self.coordinator_data.get("periods", {})
+        periods_data = self.coordinator_data.get("pricePeriods", {})
         period_data = periods_data.get(period_type)
 
         if not period_data or not period_data.get("periods"):
diff --git a/custom_components/tibber_prices/services/chartdata.py b/custom_components/tibber_prices/services/chartdata.py
index e78db1b..9599d0d 100644
--- a/custom_components/tibber_prices/services/chartdata.py
+++ b/custom_components/tibber_prices/services/chartdata.py
@@ -214,7 +214,7 @@ async def handle_chartdata(call: ServiceCall) -> dict[str, Any]:  # noqa: PLR091
     period_timestamps = None
     if period_filter:
         period_timestamps = set()
-        periods_data = coordinator.data.get("periods", {})
+        periods_data = coordinator.data.get("pricePeriods", {})
         period_data = periods_data.get(period_filter)
         if period_data:
             period_summaries = period_data.get("periods", [])
diff --git a/custom_components/tibber_prices/services/formatters.py b/custom_components/tibber_prices/services/formatters.py
index 47a4dbd..6a03077 100644
--- a/custom_components/tibber_prices/services/formatters.py
+++ b/custom_components/tibber_prices/services/formatters.py
@@ -244,7 +244,7 @@ def get_period_data(  # noqa: PLR0913, PLR0912, PLR0915
         Dictionary with period data in requested format
 
     """
-    periods_data = coordinator.data.get("periods", {})
+    periods_data = coordinator.data.get("pricePeriods", {})
     period_data = periods_data.get(period_filter)
 
     if not period_data:
diff --git a/tests/test_best_price_e2e.py b/tests/test_best_price_e2e.py
index 55753a0..ff06137 100644
--- a/tests/test_best_price_e2e.py
+++ b/tests/test_best_price_e2e.py
@@ -34,8 +34,9 @@ def _create_realistic_intervals() -> list[dict]:
     Pattern: Morning peak (6-9h), midday low (9-15h), evening moderate (15-24h).
     Daily stats: Min=30.44ct, Avg=33.26ct, Max=36.03ct
     """
-    base_time = dt_util.parse_datetime("2025-11-22T00:00:00+01:00")
-    assert base_time is not None
+    # Use CURRENT date so tests work regardless of when they run
+    now_local = dt_util.now()
+    base_time = now_local.replace(hour=0, minute=0, second=0, microsecond=0)
 
     daily_min, daily_avg, daily_max = 0.3044, 0.3326, 0.3603
 
@@ -104,6 +105,7 @@ def _create_realistic_intervals() -> list[dict]:
 
 
 @pytest.mark.unit
+@pytest.mark.freeze_time("2025-11-22 12:00:00+01:00")
 class TestBestPriceGenerationWorks:
     """Validate that best price periods generate successfully after bug fix."""
 
@@ -132,7 +134,7 @@ class TestBestPriceGenerationWorks:
         )
 
         # Calculate periods with relaxation
-        result, _ = calculate_periods_with_relaxation(
+        result = calculate_periods_with_relaxation(
             intervals,
             config=config,
             enable_relaxation=True,
@@ -171,7 +173,7 @@ class TestBestPriceGenerationWorks:
             reverse_sort=False,
         )
 
-        result_pos, _ = calculate_periods_with_relaxation(
+        result_pos = calculate_periods_with_relaxation(
             intervals,
             config=config_positive,
             enable_relaxation=True,
@@ -208,7 +210,7 @@ class TestBestPriceGenerationWorks:
             reverse_sort=False,
         )
 
-        result, _ = calculate_periods_with_relaxation(
+        result = calculate_periods_with_relaxation(
             intervals,
             config=config,
             enable_relaxation=True,
@@ -253,7 +255,7 @@ class TestBestPriceGenerationWorks:
             reverse_sort=False,
         )
 
-        result, relaxation_meta = calculate_periods_with_relaxation(
+        result = calculate_periods_with_relaxation(
             intervals,
             config=config,
             enable_relaxation=True,
@@ -269,6 +271,7 @@ class TestBestPriceGenerationWorks:
         assert len(periods) >= 2, "Relaxation should find periods"
 
         # Check if relaxation was used
+        relaxation_meta = result.get("metadata", {}).get("relaxation", {})
         if "max_flex_used" in relaxation_meta:
             max_flex_used = relaxation_meta["max_flex_used"]
             # Fix ensures reasonable flex is sufficient
@@ -276,6 +279,7 @@ class TestBestPriceGenerationWorks:
 
 
 @pytest.mark.unit
+@pytest.mark.freeze_time("2025-11-22 12:00:00+01:00")
 class TestBestPriceBugRegressionValidation:
     """Regression tests ensuring consistent behavior with peak price fix."""
 
@@ -301,7 +305,7 @@ class TestBestPriceBugRegressionValidation:
             reverse_sort=False,
         )
 
-        result, relaxation_meta = calculate_periods_with_relaxation(
+        result = calculate_periods_with_relaxation(
             intervals,
             config=config,
             enable_relaxation=True,
@@ -321,6 +325,7 @@ class TestBestPriceBugRegressionValidation:
             assert 0.10 <= flex_used <= 0.35, f"Expected flex 10-35%, got {flex_used * 100:.1f}%"
 
         # Also check relaxation metadata
+        relaxation_meta = result.get("metadata", {}).get("relaxation", {})
         if "max_flex_used" in relaxation_meta:
             max_flex = relaxation_meta["max_flex_used"]
             assert max_flex <= 0.35, f"Max flex should be reasonable, got {max_flex * 100:.1f}%"
@@ -347,7 +352,7 @@ class TestBestPriceBugRegressionValidation:
             reverse_sort=False,
         )
 
-        result, _ = calculate_periods_with_relaxation(
+        result = calculate_periods_with_relaxation(
             intervals,
             config=config,
             enable_relaxation=True,
diff --git a/tests/test_peak_price_e2e.py b/tests/test_peak_price_e2e.py
index a5b91b2..a7dbe42 100644
--- a/tests/test_peak_price_e2e.py
+++ b/tests/test_peak_price_e2e.py
@@ -34,8 +34,9 @@ def _create_realistic_intervals() -> list[dict]:
     Pattern: Morning peak (6-9h), midday low (9-15h), evening moderate (15-24h).
     Daily stats: Min=30.44ct, Avg=33.26ct, Max=36.03ct
     """
-    base_time = dt_util.parse_datetime("2025-11-22T00:00:00+01:00")
-    assert base_time is not None
+    # Use CURRENT date so tests work regardless of when they run
+    now_local = dt_util.now()
+    base_time = now_local.replace(hour=0, minute=0, second=0, microsecond=0)
 
     daily_min, daily_avg, daily_max = 0.3044, 0.3326, 0.3603
 
@@ -104,6 +105,7 @@ def _create_realistic_intervals() -> list[dict]:
 
 
 @pytest.mark.unit
+@pytest.mark.freeze_time("2025-11-22 12:00:00+01:00")
 class TestPeakPriceGenerationWorks:
     """Validate that peak price periods generate successfully after bug fix."""
 
@@ -133,7 +135,7 @@ class TestPeakPriceGenerationWorks:
         )
 
         # Calculate periods with relaxation
-        result, _ = calculate_periods_with_relaxation(
+        result = calculate_periods_with_relaxation(
             intervals,
             config=config,
             enable_relaxation=True,
@@ -173,7 +175,7 @@ class TestPeakPriceGenerationWorks:
             reverse_sort=True,
         )
 
-        result_pos, _ = calculate_periods_with_relaxation(
+        result_pos = calculate_periods_with_relaxation(
             intervals,
             config=config_positive,
             enable_relaxation=True,
@@ -210,7 +212,7 @@ class TestPeakPriceGenerationWorks:
             reverse_sort=True,
         )
 
-        result, _ = calculate_periods_with_relaxation(
+        result = calculate_periods_with_relaxation(
             intervals,
             config=config,
             enable_relaxation=True,
@@ -254,7 +256,7 @@ class TestPeakPriceGenerationWorks:
             reverse_sort=True,
         )
 
-        result, relaxation_meta = calculate_periods_with_relaxation(
+        result = calculate_periods_with_relaxation(
             intervals,
             config=config,
             enable_relaxation=True,
@@ -270,6 +272,7 @@ class TestPeakPriceGenerationWorks:
         assert len(periods) >= 2, "Relaxation should find periods"
 
         # Check if relaxation was used
+        relaxation_meta = result.get("metadata", {}).get("relaxation", {})
         if "max_flex_used" in relaxation_meta:
             max_flex_used = relaxation_meta["max_flex_used"]
             # Bug would need ~50% flex
@@ -278,6 +281,7 @@ class TestPeakPriceGenerationWorks:
 
 
 @pytest.mark.unit
+@pytest.mark.freeze_time("2025-11-22 12:00:00+01:00")
 class TestBugRegressionValidation:
     """Regression tests for the Nov 2025 sign convention bug."""
 
@@ -303,7 +307,7 @@ class TestBugRegressionValidation:
             reverse_sort=True,
         )
 
-        result, relaxation_meta = calculate_periods_with_relaxation(
+        result = calculate_periods_with_relaxation(
             intervals,
             config=config,
             enable_relaxation=True,
@@ -326,6 +330,7 @@ class TestBugRegressionValidation:
             )
 
         # Also check relaxation metadata
+        relaxation_meta = result.get("metadata", {}).get("relaxation", {})
         if "max_flex_used" in relaxation_meta:
             max_flex = relaxation_meta["max_flex_used"]
             assert max_flex <= 0.35, f"Max flex should be reasonable, got {max_flex * 100:.1f}%"
@@ -353,7 +358,7 @@ class TestBugRegressionValidation:
             reverse_sort=True,
         )
 
-        result, _ = calculate_periods_with_relaxation(
+        result = calculate_periods_with_relaxation(
             intervals,
             config=config,
             enable_relaxation=True,
diff --git a/tests/test_price_calculations.py b/tests/test_price_calculations.py
index d8b22bb..21ced4e 100644
--- a/tests/test_price_calculations.py
+++ b/tests/test_price_calculations.py
@@ -15,6 +15,9 @@ from datetime import UTC, datetime, timedelta
 
 import pytest
 
+from custom_components.tibber_prices.coordinator.time_service import (
+    TibberPricesTimeService,
+)
 from custom_components.tibber_prices.utils.price import (
     aggregate_period_levels,
     aggregate_period_ratings,
@@ -326,50 +329,64 @@ def test_rating_level_none_difference() -> None:
 
 
 @pytest.mark.parametrize(
-    ("yesterday_price", "today_price", "expected_diff", "expected_rating", "description"),
+    ("day_before_yesterday_price", "yesterday_price", "today_price", "expected_diff", "expected_rating", "description"),
     [
         # Positive prices
-        (10.0, 15.0, 50.0, "HIGH", "positive prices: day more expensive"),
-        (15.0, 10.0, -33.33, "LOW", "positive prices: day cheaper"),
-        (10.0, 10.0, 0.0, "NORMAL", "positive prices: stable"),
+        (10.0, 10.0, 15.0, 50.0, "HIGH", "positive prices: day more expensive"),
+        (15.0, 15.0, 10.0, -33.33, "LOW", "positive prices: day cheaper"),
+        (10.0, 10.0, 10.0, 0.0, "NORMAL", "positive prices: stable"),
         # Negative prices (Norway/Germany scenario)
-        (-10.0, -15.0, -50.0, "LOW", "negative prices: day more negative (cheaper)"),
-        (-15.0, -10.0, 33.33, "HIGH", "negative prices: day less negative (expensive)"),
-        (-10.0, -10.0, 0.0, "NORMAL", "negative prices: stable"),
+        (-10.0, -10.0, -15.0, -50.0, "LOW", "negative prices: day more negative (cheaper)"),
+        (-15.0, -15.0, -10.0, 33.33, "HIGH", "negative prices: day less negative (expensive)"),
+        (-10.0, -10.0, -10.0, 0.0, "NORMAL", "negative prices: stable"),
         # Transition scenarios
-        (-10.0, 0.0, 100.0, "HIGH", "transition: negative to zero"),
-        (-10.0, 10.0, 200.0, "HIGH", "transition: negative to positive"),
-        (10.0, 0.0, -100.0, "LOW", "transition: positive to zero"),
-        (10.0, -10.0, -200.0, "LOW", "transition: positive to negative"),
+        (-10.0, -10.0, 0.0, 100.0, "HIGH", "transition: negative to zero"),
+        (-10.0, -10.0, 10.0, 200.0, "HIGH", "transition: negative to positive"),
+        (10.0, 10.0, 0.0, -100.0, "LOW", "transition: positive to zero"),
+        (10.0, 10.0, -10.0, -200.0, "LOW", "transition: positive to negative"),
         # Zero scenarios
-        (0.1, 0.1, 0.0, "NORMAL", "prices near zero: stable"),
+        (0.1, 0.1, 0.1, 0.0, "NORMAL", "prices near zero: stable"),
     ],
 )
-def test_enrich_price_info_scenarios(
+def test_enrich_price_info_scenarios(  # noqa: PLR0913  # Many parameters needed for comprehensive test scenarios
+    day_before_yesterday_price: float,
     yesterday_price: float,
     today_price: float,
     expected_diff: float,
     expected_rating: str,
     description: str,
 ) -> None:
-    """Test price enrichment across various price scenarios."""
-    base = datetime(2025, 11, 22, 0, 0, 0, tzinfo=UTC)
+    """
+    Test price enrichment across various price scenarios.
 
+    CRITICAL: Tests now include day_before_yesterday data to provide full 24h lookback
+    for yesterday intervals. This matches the real API structure (192 intervals from
+    priceInfoRange + today/tomorrow).
+    """
+    base = datetime(2025, 11, 22, 0, 0, 0, tzinfo=UTC)
+    time_service = TibberPricesTimeService()
+
+    # Day before yesterday (needed for lookback)
+    day_before_yesterday = [
+        {"startsAt": base - timedelta(days=2) + timedelta(minutes=15 * i), "total": day_before_yesterday_price}
+        for i in range(96)
+    ]
+
+    # Yesterday (will be enriched using day_before_yesterday for lookback)
     yesterday = [
         {"startsAt": base - timedelta(days=1) + timedelta(minutes=15 * i), "total": yesterday_price} for i in range(96)
     ]
 
+    # Today (will be enriched using yesterday for lookback)
     today = [{"startsAt": base + timedelta(minutes=15 * i), "total": today_price} for i in range(96)]
 
-    price_info = {
-        "yesterday": yesterday,
-        "today": today,
-        "tomorrow": [],
-    }
+    # Flat list matching API structure (priceInfoRange + today)
+    all_intervals = day_before_yesterday + yesterday + today
 
-    enriched = enrich_price_info_with_differences(price_info)
+    enriched = enrich_price_info_with_differences(all_intervals, time=time_service)
 
-    first_today = enriched["today"][0]
+    # First "today" interval is at index 192 (96 day_before_yesterday + 96 yesterday)
+    first_today = enriched[192]
     assert "difference" in first_today, f"Failed for {description}: no difference field"
     assert first_today["difference"] == pytest.approx(expected_diff, rel=0.01), f"Failed for {description}"
     assert first_today["rating_level"] == expected_rating, f"Failed for {description}"
@@ -378,48 +395,57 @@ def test_enrich_price_info_scenarios(
 def test_enrich_price_info_no_yesterday_data() -> None:
     """Test enrichment when no lookback data available."""
     base = datetime(2025, 11, 22, 0, 0, 0, tzinfo=UTC)
+    time_service = TibberPricesTimeService()
 
     today = [{"startsAt": base + timedelta(minutes=15 * i), "total": 10.0} for i in range(96)]
 
-    price_info = {
-        "yesterday": [],
-        "today": today,
-        "tomorrow": [],
-    }
+    # New API: flat list (no yesterday data)
+    all_intervals = today
 
-    enriched = enrich_price_info_with_differences(price_info)
+    enriched = enrich_price_info_with_differences(all_intervals, time=time_service)
 
     # First interval has no 24h lookback → difference=None
-    first_today = enriched["today"][0]
+    first_today = enriched[0]
     assert first_today.get("difference") is None
     assert first_today.get("rating_level") is None
 
 
 def test_enrich_price_info_custom_thresholds() -> None:
-    """Test enrichment with custom rating thresholds."""
-    base = datetime(2025, 11, 22, 0, 0, 0, tzinfo=UTC)
+    """
+    Test enrichment with custom rating thresholds.
 
+    CRITICAL: Includes day_before_yesterday for full 24h lookback.
+    """
+    base = datetime(2025, 11, 22, 0, 0, 0, tzinfo=UTC)
+    time_service = TibberPricesTimeService()
+
+    # Day before yesterday (needed for lookback)
+    day_before_yesterday = [
+        {"startsAt": base - timedelta(days=2) + timedelta(minutes=15 * i), "total": 10.0} for i in range(96)
+    ]
+
+    # Yesterday (provides lookback for today)
     yesterday = [{"startsAt": base - timedelta(days=1) + timedelta(minutes=15 * i), "total": 10.0} for i in range(96)]
 
+    # Today (+10% vs yesterday average)
     today = [
         {"startsAt": base + timedelta(minutes=15 * i), "total": 11.0}  # +10% vs yesterday
         for i in range(96)
     ]
 
-    price_info = {
-        "yesterday": yesterday,
-        "today": today,
-        "tomorrow": [],
-    }
+    # Flat list matching API structure
+    all_intervals = day_before_yesterday + yesterday + today
 
     # Custom thresholds: LOW at -5%, HIGH at +5%
     enriched = enrich_price_info_with_differences(
-        price_info,
+        all_intervals,
         threshold_low=-5.0,
         threshold_high=5.0,
+        time=time_service,
     )
 
-    first_today = enriched["today"][0]
+    # First "today" interval is at index 192 (96 day_before_yesterday + 96 yesterday)
+    first_today = enriched[192]
     assert first_today["difference"] == pytest.approx(10.0, rel=1e-9)
     assert first_today["rating_level"] == "HIGH"
 
diff --git a/tests/test_sensor_consistency.py b/tests/test_sensor_consistency.py
index e7ffccc..6022e63 100644
--- a/tests/test_sensor_consistency.py
+++ b/tests/test_sensor_consistency.py
@@ -21,6 +21,7 @@ from custom_components.tibber_prices.sensor.calculators.lifecycle import (
 from homeassistant.components.binary_sensor import BinarySensorEntityDescription
 from homeassistant.exceptions import ConfigEntryAuthFailed
 from homeassistant.helpers.update_coordinator import UpdateFailed
+from homeassistant.util import dt as dt_util
 
 if TYPE_CHECKING:
     from unittest.mock import Mock as MockType
@@ -61,6 +62,48 @@ def create_mock_coordinator() -> Mock:
     return coordinator
 
 
+def create_price_intervals(day_offset: int = 0) -> list[dict]:
+    """Create 96 mock price intervals (quarter-hourly for one day)."""
+    # Use CURRENT date so tests work regardless of when they run
+    now_local = dt_util.now()
+    base_date = now_local.replace(hour=0, minute=0, second=0, microsecond=0)
+
+    intervals = []
+    for i in range(96):
+        interval_time = base_date.replace(day=base_date.day + day_offset, hour=i // 4, minute=(i % 4) * 15)
+        intervals.append(
+            {
+                "startsAt": interval_time.isoformat(),
+                "total": 20.0 + (i % 10),
+                "energy": 18.0 + (i % 10),
+                "tax": 2.0,
+                "level": "NORMAL",
+            }
+        )
+    return intervals
+
+
+def create_coordinator_data(*, today: bool = True, tomorrow: bool = False) -> dict:
+    """
+    Create coordinator data in the new flat-list format.
+
+    Args:
+        today: Include today's 96 intervals
+        tomorrow: Include tomorrow's 96 intervals
+
+    Returns:
+        Dict with flat priceInfo list: {"priceInfo": [...]}
+
+    """
+    all_intervals = []
+    if today:
+        all_intervals.extend(create_price_intervals(0))  # Today (offset 0)
+    if tomorrow:
+        all_intervals.extend(create_price_intervals(1))  # Tomorrow (offset 1)
+
+    return {"priceInfo": all_intervals}
+
+
 @pytest.fixture
 def mock_coordinator() -> MockType:
     """Fixture providing a properly mocked coordinator."""
@@ -74,7 +117,7 @@ def mock_coordinator() -> MockType:
 
 def test_connection_state_auth_failed(mock_coordinator: MockType) -> None:
     """Test connection state when auth fails - should be False (disconnected)."""
-    mock_coordinator.data = {"priceInfo": {"today": []}}  # Cached data exists
+    mock_coordinator.data = create_coordinator_data(today=True, tomorrow=False)
     mock_coordinator.last_exception = ConfigEntryAuthFailed("Invalid token")
 
     # Auth failure = definitively disconnected, even with cached data
@@ -83,7 +126,7 @@ def test_connection_state_auth_failed(mock_coordinator: MockType) -> None:
 
 def test_connection_state_api_error_with_cache(mock_coordinator: MockType) -> None:
     """Test connection state when API errors but cache available - should be True (using cache)."""
-    mock_coordinator.data = {"priceInfo": {"today": []}}  # Cached data exists
+    mock_coordinator.data = create_coordinator_data(today=True, tomorrow=False)
     mock_coordinator.last_exception = UpdateFailed("API timeout")
 
     # Other errors with cache = considered connected (degraded operation)
@@ -101,7 +144,7 @@ def test_connection_state_api_error_no_cache(mock_coordinator: MockType) -> None
 
 def test_connection_state_normal_operation(mock_coordinator: MockType) -> None:
     """Test connection state during normal operation - should be True (connected)."""
-    mock_coordinator.data = {"priceInfo": {"today": []}}
+    mock_coordinator.data = create_coordinator_data(today=True, tomorrow=False)
     mock_coordinator.last_exception = None
 
     # Normal operation with data = connected
@@ -125,7 +168,7 @@ def test_connection_state_initializing(mock_coordinator: MockType) -> None:
 def test_sensor_consistency_auth_error() -> None:
     """Test all 3 sensors are consistent when auth fails."""
     coordinator = Mock(spec=TibberPricesDataUpdateCoordinator)
-    coordinator.data = {"priceInfo": {"today": [], "tomorrow": []}}  # Cached data
+    coordinator.data = create_coordinator_data(today=True, tomorrow=False)
     coordinator.last_exception = ConfigEntryAuthFailed("Invalid token")
     coordinator.time = Mock()
     coordinator._is_fetching = False  # noqa: SLF001
@@ -143,7 +186,7 @@ def test_sensor_consistency_auth_error() -> None:
 def test_sensor_consistency_api_error_with_cache() -> None:
     """Test all 3 sensors are consistent when API errors but cache available."""
     coordinator = Mock(spec=TibberPricesDataUpdateCoordinator)
-    coordinator.data = {"priceInfo": {"today": [], "tomorrow": [{"startsAt": "2025-11-23T00:00:00+01:00"}] * 96}}
+    coordinator.data = create_coordinator_data(today=True, tomorrow=True)
     coordinator.last_exception = UpdateFailed("API timeout")
     coordinator.time = Mock()
     coordinator._is_fetching = False  # noqa: SLF001
@@ -162,7 +205,7 @@ def test_sensor_consistency_api_error_with_cache() -> None:
 def test_sensor_consistency_normal_operation() -> None:
     """Test all 3 sensors are consistent during normal operation."""
     coordinator = Mock(spec=TibberPricesDataUpdateCoordinator)
-    coordinator.data = {"priceInfo": {"today": [], "tomorrow": []}}
+    coordinator.data = create_coordinator_data(today=True, tomorrow=False)
     coordinator.last_exception = None
     coordinator.time = Mock()
     coordinator._is_fetching = False  # noqa: SLF001
@@ -186,7 +229,7 @@ def test_sensor_consistency_normal_operation() -> None:
 def test_sensor_consistency_refreshing() -> None:
     """Test all 3 sensors are consistent when actively fetching."""
     coordinator = Mock(spec=TibberPricesDataUpdateCoordinator)
-    coordinator.data = {"priceInfo": {"today": [], "tomorrow": []}}  # Previous data
+    coordinator.data = create_coordinator_data(today=True, tomorrow=False)
     coordinator.last_exception = None
     coordinator.time = Mock()
     coordinator._is_fetching = True  # noqa: SLF001 - Currently fetching
@@ -210,7 +253,7 @@ def test_sensor_consistency_refreshing() -> None:
 def test_tomorrow_data_available_auth_error_returns_none() -> None:
     """Test tomorrow_data_available returns None when auth fails (cannot check)."""
     coordinator = create_mock_coordinator()
-    coordinator.data = {"priceInfo": {"tomorrow": [{"startsAt": "2025-11-23T00:00:00+01:00"}] * 96}}  # Full data
+    coordinator.data = create_coordinator_data(today=False, tomorrow=True)
     coordinator.last_exception = ConfigEntryAuthFailed("Invalid token")
     coordinator.time = Mock()
 
@@ -247,12 +290,13 @@ def test_tomorrow_data_available_no_data_returns_none() -> None:
 def test_tomorrow_data_available_normal_operation_full_data() -> None:
     """Test tomorrow_data_available returns True when tomorrow data is complete."""
     coordinator = create_mock_coordinator()
-    coordinator.data = {"priceInfo": {"tomorrow": [{"startsAt": "2025-11-23T00:00:00+01:00"}] * 96}}
+    coordinator.data = create_coordinator_data(today=False, tomorrow=True)
     coordinator.last_exception = None
 
     # Mock time service for expected intervals calculation
+    now_date = dt_util.now().date()
     time_service = Mock()
-    time_service.get_local_date.return_value = datetime(2025, 11, 23, tzinfo=UTC).date()
+    time_service.get_local_date.return_value = now_date
     time_service.get_expected_intervals_for_day.return_value = 96  # Standard day
     coordinator.time = time_service
 
@@ -270,7 +314,7 @@ def test_tomorrow_data_available_normal_operation_full_data() -> None:
 def test_tomorrow_data_available_normal_operation_missing_data() -> None:
     """Test tomorrow_data_available returns False when tomorrow data is missing."""
     coordinator = create_mock_coordinator()
-    coordinator.data = {"priceInfo": {"tomorrow": []}}  # No tomorrow data
+    coordinator.data = create_coordinator_data(today=True, tomorrow=False)  # No tomorrow data
     coordinator.last_exception = None
 
     time_service = Mock()
@@ -306,17 +350,12 @@ def test_combined_states_auth_error_scenario() -> None:
     """
     # Setup coordinator with auth error state
     coordinator = create_mock_coordinator()
-    coordinator.data = {
-        "priceInfo": {
-            "today": [{"startsAt": "2025-11-22T00:00:00+01:00"}] * 96,
-            "tomorrow": [{"startsAt": "2025-11-23T00:00:00+01:00"}] * 96,
-        }
-    }
+    coordinator.data = create_coordinator_data(today=True, tomorrow=True)
     coordinator.last_exception = ConfigEntryAuthFailed("Invalid access token")
     coordinator._is_fetching = False  # noqa: SLF001
 
     time_service = Mock()
-    time_service.get_local_date.return_value = datetime(2025, 11, 23, tzinfo=UTC).date()
+    time_service.get_local_date.return_value = datetime(2025, 11, 22, tzinfo=UTC).date()  # Today is 22nd
     time_service.get_expected_intervals_for_day.return_value = 96
     coordinator.time = time_service
 
@@ -351,18 +390,13 @@ def test_combined_states_api_error_with_cache_scenario() -> None:
     """
     # Setup coordinator with API error but cache available
     coordinator = create_mock_coordinator()
-    coordinator.data = {
-        "priceInfo": {
-            "today": [{"startsAt": "2025-11-22T00:00:00+01:00"}] * 96,
-            "tomorrow": [{"startsAt": "2025-11-23T00:00:00+01:00"}] * 96,
-        }
-    }
+    coordinator.data = create_coordinator_data(today=True, tomorrow=True)
     coordinator.last_exception = UpdateFailed("API timeout after 30s")
     coordinator._is_fetching = False  # noqa: SLF001
     coordinator._last_price_update = datetime(2025, 11, 22, 10, 0, 0, tzinfo=UTC)  # noqa: SLF001
 
     time_service = Mock()
-    time_service.get_local_date.return_value = datetime(2025, 11, 23, tzinfo=UTC).date()
+    time_service.get_local_date.return_value = datetime(2025, 11, 22, tzinfo=UTC).date()  # Today is 22nd
     time_service.get_expected_intervals_for_day.return_value = 96
     coordinator.time = time_service
 
@@ -397,12 +431,7 @@ def test_combined_states_normal_operation_scenario() -> None:
     """
     # Setup coordinator in normal operation
     coordinator = create_mock_coordinator()
-    coordinator.data = {
-        "priceInfo": {
-            "today": [{"startsAt": "2025-11-22T00:00:00+01:00"}] * 96,
-            "tomorrow": [{"startsAt": "2025-11-23T00:00:00+01:00"}] * 96,
-        }
-    }
+    coordinator.data = create_coordinator_data(today=True, tomorrow=True)
     coordinator.last_exception = None
     coordinator._is_fetching = False  # noqa: SLF001
     coordinator._last_price_update = datetime(2025, 11, 22, 10, 0, 0, tzinfo=UTC)  # noqa: SLF001 - 10 minutes ago
@@ -412,7 +441,7 @@ def test_combined_states_normal_operation_scenario() -> None:
     time_service = Mock()
     time_service.now.return_value = now
     time_service.as_local.return_value = now
-    time_service.get_local_date.return_value = datetime(2025, 11, 23, tzinfo=UTC).date()
+    time_service.get_local_date.return_value = datetime(2025, 11, 22, tzinfo=UTC).date()  # Today is 22nd
     time_service.get_expected_intervals_for_day.return_value = 96
     coordinator.time = time_service
 
diff --git a/tests/test_tomorrow_data_refresh.py b/tests/test_tomorrow_data_refresh.py
index 8fcfb53..a426219 100644
--- a/tests/test_tomorrow_data_refresh.py
+++ b/tests/test_tomorrow_data_refresh.py
@@ -20,11 +20,15 @@ from custom_components.tibber_prices.coordinator.data_transformation import (
 from custom_components.tibber_prices.coordinator.time_service import (
     TibberPricesTimeService,
 )
+from homeassistant.util import dt as dt_util
 
 
 def create_price_intervals(day_offset: int = 0) -> list[dict]:
     """Create 96 mock price intervals (quarter-hourly for one day)."""
-    base_date = datetime(2025, 11, 22, 0, 0, 0, tzinfo=ZoneInfo("Europe/Oslo"))
+    # Use CURRENT date so tests work regardless of when they run
+    now_local = dt_util.now()
+    base_date = now_local.replace(hour=0, minute=0, second=0, microsecond=0)
+
     intervals = []
     for i in range(96):
         interval_time = base_date.replace(day=base_date.day + day_offset, hour=i // 4, minute=(i % 4) * 15)
@@ -72,7 +76,6 @@ def test_transformation_cache_invalidation_on_new_timestamp() -> None:
     transformer = TibberPricesDataTransformer(
         config_entry=config_entry,
         log_prefix="[Test]",
-        perform_turnover_fn=lambda x: x,  # No-op
         calculate_periods_fn=mock_period_calc.calculate_periods_for_price_info,
         time=time_service,
     )
@@ -81,25 +84,19 @@ def test_transformation_cache_invalidation_on_new_timestamp() -> None:
     # ================================================================
     data_t1 = {
         "timestamp": current_time,
-        "homes": {
-            "home_123": {
-                "price_info": {
-                    "yesterday": [],
-                    "today": create_price_intervals(0),
-                    "tomorrow": [],  # NO TOMORROW YET
-                    "currency": "EUR",
-                }
-            }
-        },
+        "home_id": "home_123",
+        "price_info": create_price_intervals(0),  # Today only
+        "currency": "EUR",
     }
 
-    result_t1 = transformer.transform_data_for_main_entry(data_t1)
+    result_t1 = transformer.transform_data(data_t1)
     assert result_t1 is not None
-    assert result_t1["priceInfo"]["tomorrow"] == []
+    # In new flat structure, priceInfo is a list with only today's intervals (96)
+    assert len(result_t1["priceInfo"]) == 96
 
     # STEP 2: Second call with SAME timestamp should use cache
     # =========================================================
-    result_t1_cached = transformer.transform_data_for_main_entry(data_t1)
+    result_t1_cached = transformer.transform_data(data_t1)
     assert result_t1_cached is result_t1  # SAME object (cached)
 
     # STEP 3: Third call with DIFFERENT timestamp should NOT use cache
@@ -107,24 +104,17 @@ def test_transformation_cache_invalidation_on_new_timestamp() -> None:
     new_time = current_time + timedelta(minutes=1)
     data_t2 = {
         "timestamp": new_time,  # DIFFERENT timestamp
-        "homes": {
-            "home_123": {
-                "price_info": {
-                    "yesterday": [],
-                    "today": create_price_intervals(0),
-                    "tomorrow": create_price_intervals(1),  # NOW HAS TOMORROW
-                    "currency": "EUR",
-                }
-            }
-        },
+        "home_id": "home_123",
+        "price_info": create_price_intervals(0) + create_price_intervals(1),  # Today + Tomorrow
+        "currency": "EUR",
     }
 
-    result_t2 = transformer.transform_data_for_main_entry(data_t2)
+    result_t2 = transformer.transform_data(data_t2)
 
     # CRITICAL ASSERTIONS: Cache must be invalidated
     assert result_t2 is not result_t1  # DIFFERENT object (re-transformed)
-    assert len(result_t2["priceInfo"]["tomorrow"]) == 96  # New data present
-    assert "periods" in result_t2  # Periods recalculated
+    assert len(result_t2["priceInfo"]) == 192  # Today (96) + Tomorrow (96)
+    assert "pricePeriods" in result_t2  # Periods recalculated
 
 
 @pytest.mark.unit
@@ -158,31 +148,23 @@ def test_cache_behavior_on_config_change() -> None:
     transformer = TibberPricesDataTransformer(
         config_entry=config_entry,
         log_prefix="[Test]",
-        perform_turnover_fn=lambda x: x,
         calculate_periods_fn=mock_period_calc.calculate_periods_for_price_info,
         time=time_service,
     )
 
     data = {
         "timestamp": current_time,
-        "homes": {
-            "home_123": {
-                "price_info": {
-                    "yesterday": [],
-                    "today": create_price_intervals(0),
-                    "tomorrow": create_price_intervals(1),
-                    "currency": "EUR",
-                }
-            }
-        },
+        "home_id": "home_123",
+        "price_info": create_price_intervals(0) + create_price_intervals(1),  # Today + Tomorrow
+        "currency": "EUR",
     }
 
     # First transformation
-    result_1 = transformer.transform_data_for_main_entry(data)
+    result_1 = transformer.transform_data(data)
     assert result_1 is not None
 
     # Second call with SAME config and timestamp should use cache
-    result_1_cached = transformer.transform_data_for_main_entry(data)
+    result_1_cached = transformer.transform_data(data)
     assert result_1_cached is result_1  # SAME object
 
     # Change config (note: in real system, config change triggers coordinator reload)
@@ -193,7 +175,7 @@ def test_cache_behavior_on_config_change() -> None:
 
     # Call with SAME timestamp but DIFFERENT config
     # Current behavior: Still uses cache (acceptable, see docstring)
-    result_2 = transformer.transform_data_for_main_entry(data)
+    result_2 = transformer.transform_data(data)
     assert result_2 is result_1  # SAME object (cache preserved)
 
 
@@ -224,29 +206,21 @@ def test_cache_preserved_when_neither_timestamp_nor_config_changed() -> None:
     transformer = TibberPricesDataTransformer(
         config_entry=config_entry,
         log_prefix="[Test]",
-        perform_turnover_fn=lambda x: x,
         calculate_periods_fn=mock_period_calc.calculate_periods_for_price_info,
         time=time_service,
     )
 
     data = {
         "timestamp": current_time,
-        "homes": {
-            "home_123": {
-                "price_info": {
-                    "yesterday": [],
-                    "today": create_price_intervals(0),
-                    "tomorrow": create_price_intervals(1),
-                    "currency": "EUR",
-                }
-            }
-        },
+        "home_id": "home_123",
+        "price_info": create_price_intervals(0) + create_price_intervals(1),  # Today + Tomorrow
+        "currency": "EUR",
     }
 
     # Multiple calls with unchanged data/config should all use cache
-    result_1 = transformer.transform_data_for_main_entry(data)
-    result_2 = transformer.transform_data_for_main_entry(data)
-    result_3 = transformer.transform_data_for_main_entry(data)
+    result_1 = transformer.transform_data(data)
+    result_2 = transformer.transform_data(data)
+    result_3 = transformer.transform_data(data)
 
     assert result_1 is result_2 is result_3  # ALL same object (cached)