diff --git a/.coveragerc b/.coveragerc
index 322c7e1af48..d75eb6aa9d6 100644
--- a/.coveragerc
+++ b/.coveragerc
@@ -1178,6 +1178,8 @@ omit =
     homeassistant/components/waterfurnace/*
     homeassistant/components/watson_iot/*
     homeassistant/components/watson_tts/tts.py
+    homeassistant/components/watttime/__init__.py
+    homeassistant/components/watttime/sensor.py
     homeassistant/components/waze_travel_time/__init__.py
     homeassistant/components/waze_travel_time/helpers.py
     homeassistant/components/waze_travel_time/sensor.py
diff --git a/CODEOWNERS b/CODEOWNERS
index bc3f6f6f838..76748306cfe 100644
--- a/CODEOWNERS
+++ b/CODEOWNERS
@@ -574,6 +574,7 @@ homeassistant/components/wake_on_lan/* @ntilley905
 homeassistant/components/wallbox/* @hesselonline
 homeassistant/components/waqi/* @andrey-git
 homeassistant/components/watson_tts/* @rutkai
+homeassistant/components/watttime/* @bachya
 homeassistant/components/weather/* @fabaff
 homeassistant/components/webostv/* @bendavid @thecode
 homeassistant/components/websocket_api/* @home-assistant/core
diff --git a/homeassistant/components/watttime/__init__.py b/homeassistant/components/watttime/__init__.py
new file mode 100644
index 00000000000..d376dd40db6
--- /dev/null
+++ b/homeassistant/components/watttime/__init__.py
@@ -0,0 +1,78 @@
+"""The WattTime integration."""
+from __future__ import annotations
+
+from datetime import timedelta
+
+from aiowatttime import Client
+from aiowatttime.emissions import RealTimeEmissionsResponseType
+from aiowatttime.errors import WattTimeError
+
+from homeassistant.config_entries import ConfigEntry
+from homeassistant.const import (
+    CONF_LATITUDE,
+    CONF_LONGITUDE,
+    CONF_PASSWORD,
+    CONF_USERNAME,
+)
+from homeassistant.core import HomeAssistant
+from homeassistant.helpers import aiohttp_client
+from homeassistant.helpers.update_coordinator import DataUpdateCoordinator, UpdateFailed
+
+from .const import DATA_COORDINATOR, DOMAIN, LOGGER
+
+DEFAULT_UPDATE_INTERVAL = timedelta(minutes=5)
+
+PLATFORMS: list[str] = ["sensor"]
+
+
+async def async_setup_entry(hass: HomeAssistant, entry: ConfigEntry) -> bool:
+    """Set up WattTime from a config entry."""
+    hass.data.setdefault(DOMAIN, {DATA_COORDINATOR: {}})
+
+    session = aiohttp_client.async_get_clientsession(hass)
+
+    try:
+        client = await Client.async_login(
+            entry.data[CONF_USERNAME],
+            entry.data[CONF_PASSWORD],
+            session=session,
+            logger=LOGGER,
+        )
+    except WattTimeError as err:
+        LOGGER.error("Error while authenticating with WattTime: %s", err)
+        return False
+
+    async def async_update_data() -> RealTimeEmissionsResponseType:
+        """Get the latest realtime emissions data."""
+        try:
+            return await client.emissions.async_get_realtime_emissions(
+                entry.data[CONF_LATITUDE], entry.data[CONF_LONGITUDE]
+            )
+        except WattTimeError as err:
+            raise UpdateFailed(
+                f"Error while requesting data from WattTime: {err}"
+            ) from err
+
+    coordinator = DataUpdateCoordinator(
+        hass,
+        LOGGER,
+        name=entry.title,
+        update_interval=DEFAULT_UPDATE_INTERVAL,
+        update_method=async_update_data,
+    )
+
+    await coordinator.async_config_entry_first_refresh()
+    hass.data[DOMAIN][DATA_COORDINATOR][entry.entry_id] = coordinator
+
+    hass.config_entries.async_setup_platforms(entry, PLATFORMS)
+
+    return True
+
+
+async def async_unload_entry(hass: HomeAssistant, entry: ConfigEntry) -> bool:
+    """Unload a config entry."""
+    unload_ok = await hass.config_entries.async_unload_platforms(entry, PLATFORMS)
+    if unload_ok:
+        hass.data[DOMAIN][DATA_COORDINATOR].pop(entry.entry_id)
+
+    return unload_ok
diff --git a/homeassistant/components/watttime/config_flow.py b/homeassistant/components/watttime/config_flow.py
new file mode 100644
index 00000000000..a6c5dd422c2
--- /dev/null
+++ b/homeassistant/components/watttime/config_flow.py
@@ -0,0 +1,165 @@
+"""Config flow for WattTime integration."""
+from __future__ import annotations
+
+from typing import TYPE_CHECKING, Any
+
+from aiowatttime import Client
+from aiowatttime.errors import CoordinatesNotFoundError, InvalidCredentialsError
+import voluptuous as vol
+
+from homeassistant import config_entries
+from homeassistant.const import (
+    CONF_LATITUDE,
+    CONF_LONGITUDE,
+    CONF_PASSWORD,
+    CONF_USERNAME,
+)
+from homeassistant.data_entry_flow import FlowResult
+from homeassistant.helpers import aiohttp_client, config_validation as cv
+
+from .const import (
+    CONF_BALANCING_AUTHORITY,
+    CONF_BALANCING_AUTHORITY_ABBREV,
+    DOMAIN,
+    LOGGER,
+)
+
+CONF_LOCATION_TYPE = "location_type"
+
+LOCATION_TYPE_COORDINATES = "Specify coordinates"
+LOCATION_TYPE_HOME = "Use home location"
+
+STEP_COORDINATES_DATA_SCHEMA = vol.Schema(
+    {
+        vol.Required(CONF_LATITUDE): cv.latitude,
+        vol.Required(CONF_LONGITUDE): cv.longitude,
+    }
+)
+
+STEP_LOCATION_DATA_SCHEMA = vol.Schema(
+    {
+        vol.Required(CONF_LOCATION_TYPE): vol.In(
+            [LOCATION_TYPE_HOME, LOCATION_TYPE_COORDINATES]
+        ),
+    }
+)
+
+STEP_USER_DATA_SCHEMA = vol.Schema(
+    {
+        vol.Required(CONF_USERNAME): str,
+        vol.Required(CONF_PASSWORD): str,
+    }
+)
+
+
+class ConfigFlow(config_entries.ConfigFlow, domain=DOMAIN):
+    """Handle a config flow for WattTime."""
+
+    VERSION = 1
+
+    def __init__(self) -> None:
+        """Initialize."""
+        self._client: Client | None = None
+        self._password: str | None = None
+        self._username: str | None = None
+
+    async def async_step_coordinates(
+        self, user_input: dict[str, Any] | None = None
+    ) -> FlowResult:
+        """Handle the coordinates step."""
+        if not user_input:
+            return self.async_show_form(
+                step_id="coordinates", data_schema=STEP_COORDINATES_DATA_SCHEMA
+            )
+
+        if TYPE_CHECKING:
+            assert self._client
+
+        unique_id = f"{user_input[CONF_LATITUDE]}, {user_input[CONF_LONGITUDE]}"
+        await self.async_set_unique_id(unique_id)
+        self._abort_if_unique_id_configured()
+
+        try:
+            grid_region = await self._client.emissions.async_get_grid_region(
+                user_input[CONF_LATITUDE], user_input[CONF_LONGITUDE]
+            )
+        except CoordinatesNotFoundError:
+            return self.async_show_form(
+                step_id="coordinates",
+                data_schema=STEP_COORDINATES_DATA_SCHEMA,
+                errors={CONF_LATITUDE: "unknown_coordinates"},
+            )
+        except Exception as err:  # pylint: disable=broad-except
+            LOGGER.exception("Unexpected exception while getting region: %s", err)
+            return self.async_show_form(
+                step_id="coordinates",
+                data_schema=STEP_COORDINATES_DATA_SCHEMA,
+                errors={"base": "unknown"},
+            )
+
+        return self.async_create_entry(
+            title=unique_id,
+            data={
+                CONF_USERNAME: self._username,
+                CONF_PASSWORD: self._password,
+                CONF_LATITUDE: user_input[CONF_LATITUDE],
+                CONF_LONGITUDE: user_input[CONF_LONGITUDE],
+                CONF_BALANCING_AUTHORITY: grid_region["name"],
+                CONF_BALANCING_AUTHORITY_ABBREV: grid_region["abbrev"],
+            },
+        )
+
+    async def async_step_location(
+        self, user_input: dict[str, Any] | None = None
+    ) -> FlowResult:
+        """Handle the "pick a location" step."""
+        if not user_input:
+            return self.async_show_form(
+                step_id="location", data_schema=STEP_LOCATION_DATA_SCHEMA
+            )
+
+        if user_input[CONF_LOCATION_TYPE] == LOCATION_TYPE_COORDINATES:
+            return self.async_show_form(
+                step_id="coordinates", data_schema=STEP_COORDINATES_DATA_SCHEMA
+            )
+        return await self.async_step_coordinates(
+            {
+                CONF_LATITUDE: self.hass.config.latitude,
+                CONF_LONGITUDE: self.hass.config.longitude,
+            }
+        )
+
+    async def async_step_user(
+        self, user_input: dict[str, Any] | None = None
+    ) -> FlowResult:
+        """Handle the initial step."""
+        if not user_input:
+            return self.async_show_form(
+                step_id="user", data_schema=STEP_USER_DATA_SCHEMA
+            )
+
+        session = aiohttp_client.async_get_clientsession(self.hass)
+
+        try:
+            self._client = await Client.async_login(
+                user_input[CONF_USERNAME],
+                user_input[CONF_PASSWORD],
+                session=session,
+            )
+        except InvalidCredentialsError:
+            return self.async_show_form(
+                step_id="user",
+                data_schema=STEP_USER_DATA_SCHEMA,
+                errors={CONF_USERNAME: "invalid_auth"},
+            )
+        except Exception as err:  # pylint: disable=broad-except
+            LOGGER.exception("Unexpected exception while logging in: %s", err)
+            return self.async_show_form(
+                step_id="user",
+                data_schema=STEP_USER_DATA_SCHEMA,
+                errors={"base": "unknown"},
+            )
+
+        self._username = user_input[CONF_USERNAME]
+        self._password = user_input[CONF_PASSWORD]
+        return await self.async_step_location()
diff --git a/homeassistant/components/watttime/const.py b/homeassistant/components/watttime/const.py
new file mode 100644
index 00000000000..680505c8d43
--- /dev/null
+++ b/homeassistant/components/watttime/const.py
@@ -0,0 +1,11 @@
+"""Constants for the WattTime integration."""
+import logging
+
+DOMAIN = "watttime"
+
+LOGGER = logging.getLogger(__package__)
+
+CONF_BALANCING_AUTHORITY = "balancing_authority"
+CONF_BALANCING_AUTHORITY_ABBREV = "balancing_authority_abbreviation"
+
+DATA_COORDINATOR = "coordinator"
diff --git a/homeassistant/components/watttime/manifest.json b/homeassistant/components/watttime/manifest.json
new file mode 100644
index 00000000000..d4000b6f6b1
--- /dev/null
+++ b/homeassistant/components/watttime/manifest.json
@@ -0,0 +1,17 @@
+{
+  "domain": "watttime",
+  "name": "WattTime",
+  "config_flow": true,
+  "documentation": "https://www.home-assistant.io/integrations/watttime",
+  "requirements": [
+    "aiowatttime==0.1.1"
+  ],
+  "ssdp": [],
+  "zeroconf": [],
+  "homekit": {},
+  "dependencies": [],
+  "codeowners": [
+    "@bachya"
+  ],
+  "iot_class": "cloud_polling"
+}
diff --git a/homeassistant/components/watttime/sensor.py b/homeassistant/components/watttime/sensor.py
new file mode 100644
index 00000000000..f44249ecde1
--- /dev/null
+++ b/homeassistant/components/watttime/sensor.py
@@ -0,0 +1,134 @@
+"""Support for WattTime sensors."""
+from __future__ import annotations
+
+from dataclasses import dataclass
+from typing import TYPE_CHECKING
+
+from homeassistant.components.sensor import (
+    STATE_CLASS_MEASUREMENT,
+    SensorEntity,
+    SensorEntityDescription,
+)
+from homeassistant.config_entries import ConfigEntry
+from homeassistant.const import (
+    ATTR_ATTRIBUTION,
+    ATTR_LATITUDE,
+    ATTR_LONGITUDE,
+    MASS_POUNDS,
+    PERCENTAGE,
+)
+from homeassistant.core import HomeAssistant, callback
+from homeassistant.helpers.entity_platform import AddEntitiesCallback
+from homeassistant.helpers.update_coordinator import (
+    CoordinatorEntity,
+    DataUpdateCoordinator,
+)
+
+from .const import (
+    CONF_BALANCING_AUTHORITY,
+    CONF_BALANCING_AUTHORITY_ABBREV,
+    DATA_COORDINATOR,
+    DOMAIN,
+)
+
+ATTR_BALANCING_AUTHORITY = "balancing_authority"
+
+DEFAULT_ATTRIBUTION = "Pickup data provided by WattTime"
+
+SENSOR_TYPE_REALTIME_EMISSIONS_MOER = "realtime_emissions_moer"
+SENSOR_TYPE_REALTIME_EMISSIONS_PERCENT = "realtime_emissions_percent"
+
+
+@dataclass
+class RealtimeEmissionsSensorDescriptionMixin:
+    """Define an entity description mixin for realtime emissions sensors."""
+
+    data_key: str
+
+
+@dataclass
+class RealtimeEmissionsSensorEntityDescription(
+    SensorEntityDescription, RealtimeEmissionsSensorDescriptionMixin
+):
+    """Describe a realtime emissions sensor."""
+
+
+REALTIME_EMISSIONS_SENSOR_DESCRIPTIONS = (
+    RealtimeEmissionsSensorEntityDescription(
+        key=SENSOR_TYPE_REALTIME_EMISSIONS_MOER,
+        name="Marginal Operating Emissions Rate",
+        icon="mdi:blur",
+        native_unit_of_measurement=f"{MASS_POUNDS} CO2/MWh",
+        state_class=STATE_CLASS_MEASUREMENT,
+        data_key="moer",
+    ),
+    RealtimeEmissionsSensorEntityDescription(
+        key=SENSOR_TYPE_REALTIME_EMISSIONS_PERCENT,
+        name="Relative Marginal Emissions Intensity",
+        icon="mdi:blur",
+        native_unit_of_measurement=PERCENTAGE,
+        state_class=STATE_CLASS_MEASUREMENT,
+        data_key="percent",
+    ),
+)
+
+
+async def async_setup_entry(
+    hass: HomeAssistant, entry: ConfigEntry, async_add_entities: AddEntitiesCallback
+) -> None:
+    """Set up WattTime sensors based on a config entry."""
+    coordinator = hass.data[DOMAIN][DATA_COORDINATOR][entry.entry_id]
+    async_add_entities(
+        [
+            RealtimeEmissionsSensor(coordinator, description)
+            for description in REALTIME_EMISSIONS_SENSOR_DESCRIPTIONS
+            if description.data_key in coordinator.data
+        ]
+    )
+
+
+class RealtimeEmissionsSensor(CoordinatorEntity, SensorEntity):
+    """Define a realtime emissions sensor."""
+
+    entity_description: RealtimeEmissionsSensorEntityDescription
+
+    def __init__(
+        self,
+        coordinator: DataUpdateCoordinator,
+        description: RealtimeEmissionsSensorEntityDescription,
+    ) -> None:
+        """Initialize the sensor."""
+        super().__init__(coordinator)
+
+        if TYPE_CHECKING:
+            assert coordinator.config_entry
+
+        self._attr_extra_state_attributes = {
+            ATTR_ATTRIBUTION: DEFAULT_ATTRIBUTION,
+            ATTR_BALANCING_AUTHORITY: coordinator.config_entry.data[
+                CONF_BALANCING_AUTHORITY
+            ],
+            ATTR_LATITUDE: coordinator.config_entry.data[ATTR_LATITUDE],
+            ATTR_LONGITUDE: coordinator.config_entry.data[ATTR_LONGITUDE],
+        }
+        self._attr_name = f"{description.name} ({coordinator.config_entry.data[CONF_BALANCING_AUTHORITY_ABBREV]})"
+        self._attr_unique_id = f"{coordinator.config_entry.entry_id}_{description.key}"
+        self.entity_description = description
+
+    @callback
+    def _handle_coordinator_update(self) -> None:
+        """Respond to a DataUpdateCoordinator update."""
+        self.update_from_latest_data()
+        self.async_write_ha_state()
+
+    async def async_added_to_hass(self) -> None:
+        """Handle entity which will be added."""
+        await super().async_added_to_hass()
+        self.update_from_latest_data()
+
+    @callback
+    def update_from_latest_data(self) -> None:
+        """Update the state."""
+        self._attr_native_value = self.coordinator.data[
+            self.entity_description.data_key
+        ]
diff --git a/homeassistant/components/watttime/strings.json b/homeassistant/components/watttime/strings.json
new file mode 100644
index 00000000000..34dc253dcde
--- /dev/null
+++ b/homeassistant/components/watttime/strings.json
@@ -0,0 +1,34 @@
+{
+  "config": {
+    "step": {
+      "coordinates": {
+        "description": "Input the latitude and longitude to monitor:",
+        "data": {
+          "latitude": "[%key:common::config_flow::data::latitude%]",
+          "longitude": "[%key:common::config_flow::data::longitude%]"
+        }
+      },
+      "location": {
+        "description": "Pick a location to monitor:",
+        "data": {
+          "location_type": "[%key:common::config_flow::data::location%]"
+        }
+      },
+      "user": {
+        "description": "Input your username and password:",
+        "data": {
+          "username": "[%key:common::config_flow::data::username%]",
+          "password": "[%key:common::config_flow::data::password%]"
+        }
+      }
+    },
+    "error": {
+      "invalid_auth": "[%key:common::config_flow::error::invalid_auth%]",
+      "unknown": "[%key:common::config_flow::error::unknown%]",
+      "unknown_coordinates": "No data for latitude/longitude"
+    },
+    "abort": {
+      "already_configured": "[%key:common::config_flow::abort::already_configured_device%]"
+    }
+  }
+}
diff --git a/homeassistant/components/watttime/translations/en.json b/homeassistant/components/watttime/translations/en.json
new file mode 100644
index 00000000000..44ae51fae53
--- /dev/null
+++ b/homeassistant/components/watttime/translations/en.json
@@ -0,0 +1,34 @@
+{
+    "config": {
+        "abort": {
+            "already_configured": "Device is already configured"
+        },
+        "error": {
+            "invalid_auth": "Invalid authentication",
+            "unknown": "Unexpected error",
+            "unknown_coordinates": "No data for latitude/longitude"
+        },
+        "step": {
+            "coordinates": {
+                "data": {
+                    "latitude": "Latitude",
+                    "longitude": "Longitude"
+                },
+                "description": "Input the latitude and longitude to monitor:"
+            },
+            "location": {
+                "data": {
+                    "location_type": "Location"
+                },
+                "description": "Pick a location to monitor:"
+            },
+            "user": {
+                "data": {
+                    "password": "Password",
+                    "username": "Username"
+                },
+                "description": "Input your username and password:"
+            }
+        }
+    }
+}
\ No newline at end of file
diff --git a/homeassistant/generated/config_flows.py b/homeassistant/generated/config_flows.py
index 80395e8e3f6..0983da03f98 100644
--- a/homeassistant/generated/config_flows.py
+++ b/homeassistant/generated/config_flows.py
@@ -303,6 +303,7 @@ FLOWS = [
     "vizio",
     "volumio",
     "wallbox",
+    "watttime",
     "waze_travel_time",
     "wemo",
     "whirlpool",
diff --git a/requirements_all.txt b/requirements_all.txt
index 13ea083eb12..986b79e278d 100644
--- a/requirements_all.txt
+++ b/requirements_all.txt
@@ -254,6 +254,9 @@ aiotractive==0.5.2
 # homeassistant.components.unifi
 aiounifi==26
 
+# homeassistant.components.watttime
+aiowatttime==0.1.1
+
 # homeassistant.components.yandex_transport
 aioymaps==1.1.0
 
diff --git a/requirements_test_all.txt b/requirements_test_all.txt
index 3238c57590f..c0dff9c66d4 100644
--- a/requirements_test_all.txt
+++ b/requirements_test_all.txt
@@ -178,6 +178,9 @@ aiotractive==0.5.2
 # homeassistant.components.unifi
 aiounifi==26
 
+# homeassistant.components.watttime
+aiowatttime==0.1.1
+
 # homeassistant.components.yandex_transport
 aioymaps==1.1.0
 
diff --git a/tests/components/watttime/__init__.py b/tests/components/watttime/__init__.py
new file mode 100644
index 00000000000..6e01f28b518
--- /dev/null
+++ b/tests/components/watttime/__init__.py
@@ -0,0 +1 @@
+"""Tests for the WattTime integration."""
diff --git a/tests/components/watttime/test_config_flow.py b/tests/components/watttime/test_config_flow.py
new file mode 100644
index 00000000000..a3d2867eb2d
--- /dev/null
+++ b/tests/components/watttime/test_config_flow.py
@@ -0,0 +1,263 @@
+"""Test the WattTime config flow."""
+from unittest.mock import AsyncMock, patch
+
+from aiowatttime.errors import CoordinatesNotFoundError, InvalidCredentialsError
+import pytest
+
+from homeassistant import config_entries, setup
+from homeassistant.components.watttime.config_flow import (
+    CONF_LOCATION_TYPE,
+    LOCATION_TYPE_COORDINATES,
+    LOCATION_TYPE_HOME,
+)
+from homeassistant.components.watttime.const import (
+    CONF_BALANCING_AUTHORITY,
+    CONF_BALANCING_AUTHORITY_ABBREV,
+    DOMAIN,
+)
+from homeassistant.const import (
+    CONF_LATITUDE,
+    CONF_LONGITUDE,
+    CONF_PASSWORD,
+    CONF_USERNAME,
+)
+from homeassistant.core import HomeAssistant
+from homeassistant.data_entry_flow import (
+    RESULT_TYPE_ABORT,
+    RESULT_TYPE_CREATE_ENTRY,
+    RESULT_TYPE_FORM,
+)
+
+from tests.common import MockConfigEntry
+
+
+@pytest.fixture(name="client")
+def client_fixture(get_grid_region):
+    """Define a fixture for an aiowatttime client."""
+    client = AsyncMock(return_value=None)
+    client.emissions.async_get_grid_region = get_grid_region
+    return client
+
+
+@pytest.fixture(name="client_login")
+def client_login_fixture(client):
+    """Define a fixture for patching the aiowatttime coroutine to get a client."""
+    with patch("homeassistant.components.watttime.config_flow.Client.async_login") as m:
+        m.return_value = client
+        yield m
+
+
+@pytest.fixture(name="get_grid_region")
+def get_grid_region_fixture():
+    """Define a fixture for getting grid region data."""
+    return AsyncMock(return_value={"abbrev": "AUTH_1", "id": 1, "name": "Authority 1"})
+
+
+async def test_duplicate_error(hass: HomeAssistant, client_login):
+    """Test that errors are shown when duplicate entries are added."""
+    MockConfigEntry(
+        domain=DOMAIN,
+        unique_id="32.87336, -117.22743",
+        data={
+            CONF_USERNAME: "user",
+            CONF_PASSWORD: "password",
+            CONF_LATITUDE: 32.87336,
+            CONF_LONGITUDE: -117.22743,
+        },
+    ).add_to_hass(hass)
+
+    result = await hass.config_entries.flow.async_init(
+        DOMAIN,
+        context={"source": config_entries.SOURCE_USER},
+        data={CONF_USERNAME: "user", CONF_PASSWORD: "password"},
+    )
+    result = await hass.config_entries.flow.async_configure(
+        result["flow_id"],
+        user_input={CONF_LOCATION_TYPE: LOCATION_TYPE_HOME},
+    )
+    await hass.async_block_till_done()
+
+    assert result["type"] == RESULT_TYPE_ABORT
+    assert result["reason"] == "already_configured"
+
+
+async def test_show_form_coordinates(hass: HomeAssistant) -> None:
+    """Test showing the form to input custom latitude/longitude."""
+    result = await hass.config_entries.flow.async_init(
+        DOMAIN, context={"source": config_entries.SOURCE_USER}
+    )
+    result = await hass.config_entries.flow.async_configure(
+        result["flow_id"],
+        user_input={CONF_USERNAME: "user", CONF_PASSWORD: "password"},
+    )
+    result = await hass.config_entries.flow.async_configure(
+        result["flow_id"],
+        user_input={CONF_LOCATION_TYPE: LOCATION_TYPE_COORDINATES},
+    )
+    result = await hass.config_entries.flow.async_configure(result["flow_id"])
+    await hass.async_block_till_done()
+
+    assert result["type"] == RESULT_TYPE_FORM
+    assert result["step_id"] == "coordinates"
+    assert result["errors"] is None
+
+
+async def test_show_form_user(hass: HomeAssistant) -> None:
+    """Test showing the form to select the authentication type."""
+    result = await hass.config_entries.flow.async_init(
+        DOMAIN, context={"source": config_entries.SOURCE_USER}
+    )
+    await hass.async_block_till_done()
+
+    assert result["type"] == RESULT_TYPE_FORM
+    assert result["step_id"] == "user"
+    assert result["errors"] is None
+
+
+@pytest.mark.parametrize(
+    "get_grid_region", [AsyncMock(side_effect=CoordinatesNotFoundError)]
+)
+async def test_step_coordinates_unknown_coordinates(
+    hass: HomeAssistant, client_login
+) -> None:
+    """Test that providing coordinates with no data is handled."""
+    await setup.async_setup_component(hass, "persistent_notification", {})
+    result = await hass.config_entries.flow.async_init(
+        DOMAIN,
+        context={"source": config_entries.SOURCE_USER},
+        data={CONF_USERNAME: "user", CONF_PASSWORD: "password"},
+    )
+    result = await hass.config_entries.flow.async_configure(
+        result["flow_id"],
+        user_input={CONF_LOCATION_TYPE: LOCATION_TYPE_COORDINATES},
+    )
+    result = await hass.config_entries.flow.async_configure(
+        result["flow_id"],
+        user_input={CONF_LATITUDE: "0", CONF_LONGITUDE: "0"},
+    )
+    await hass.async_block_till_done()
+
+    assert result["type"] == RESULT_TYPE_FORM
+    assert result["errors"] == {"latitude": "unknown_coordinates"}
+
+
+@pytest.mark.parametrize("get_grid_region", [AsyncMock(side_effect=Exception)])
+async def test_step_coordinates_unknown_error(
+    hass: HomeAssistant, client_login
+) -> None:
+    """Test that providing coordinates with no data is handled."""
+    await setup.async_setup_component(hass, "persistent_notification", {})
+    result = await hass.config_entries.flow.async_init(
+        DOMAIN,
+        context={"source": config_entries.SOURCE_USER},
+        data={CONF_USERNAME: "user", CONF_PASSWORD: "password"},
+    )
+    result = await hass.config_entries.flow.async_configure(
+        result["flow_id"],
+        user_input={CONF_LOCATION_TYPE: LOCATION_TYPE_HOME},
+    )
+    await hass.async_block_till_done()
+
+    assert result["type"] == RESULT_TYPE_FORM
+    assert result["errors"] == {"base": "unknown"}
+
+
+async def test_step_login_coordinates(hass: HomeAssistant, client_login) -> None:
+    """Test a full login flow (inputting custom coordinates)."""
+    await setup.async_setup_component(hass, "persistent_notification", {})
+    with patch(
+        "homeassistant.components.watttime.async_setup_entry",
+        return_value=True,
+    ):
+        result = await hass.config_entries.flow.async_init(
+            DOMAIN,
+            context={"source": config_entries.SOURCE_USER},
+            data={CONF_USERNAME: "user", CONF_PASSWORD: "password"},
+        )
+        result = await hass.config_entries.flow.async_configure(
+            result["flow_id"],
+            user_input={CONF_LOCATION_TYPE: LOCATION_TYPE_COORDINATES},
+        )
+        result = await hass.config_entries.flow.async_configure(
+            result["flow_id"],
+            user_input={CONF_LATITUDE: "51.528308", CONF_LONGITUDE: "-0.3817765"},
+        )
+        await hass.async_block_till_done()
+
+    assert result["type"] == RESULT_TYPE_CREATE_ENTRY
+    assert result["title"] == "51.528308, -0.3817765"
+    assert result["data"] == {
+        CONF_USERNAME: "user",
+        CONF_PASSWORD: "password",
+        CONF_LATITUDE: 51.528308,
+        CONF_LONGITUDE: -0.3817765,
+        CONF_BALANCING_AUTHORITY: "Authority 1",
+        CONF_BALANCING_AUTHORITY_ABBREV: "AUTH_1",
+    }
+
+
+async def test_step_user_home(hass: HomeAssistant, client_login) -> None:
+    """Test a full login flow (selecting the home location)."""
+    await setup.async_setup_component(hass, "persistent_notification", {})
+    with patch(
+        "homeassistant.components.watttime.async_setup_entry",
+        return_value=True,
+    ):
+        result = await hass.config_entries.flow.async_init(
+            DOMAIN,
+            context={"source": config_entries.SOURCE_USER},
+            data={CONF_USERNAME: "user", CONF_PASSWORD: "password"},
+        )
+        result = await hass.config_entries.flow.async_configure(
+            result["flow_id"],
+            user_input={CONF_LOCATION_TYPE: LOCATION_TYPE_HOME},
+        )
+        await hass.async_block_till_done()
+
+    assert result["type"] == RESULT_TYPE_CREATE_ENTRY
+    assert result["title"] == "32.87336, -117.22743"
+    assert result["data"] == {
+        CONF_USERNAME: "user",
+        CONF_PASSWORD: "password",
+        CONF_LATITUDE: 32.87336,
+        CONF_LONGITUDE: -117.22743,
+        CONF_BALANCING_AUTHORITY: "Authority 1",
+        CONF_BALANCING_AUTHORITY_ABBREV: "AUTH_1",
+    }
+
+
+async def test_step_user_invalid_credentials(hass: HomeAssistant) -> None:
+    """Test that invalid credentials are handled."""
+    await setup.async_setup_component(hass, "persistent_notification", {})
+    with patch(
+        "homeassistant.components.watttime.config_flow.Client.async_login",
+        AsyncMock(side_effect=InvalidCredentialsError),
+    ):
+        result = await hass.config_entries.flow.async_init(
+            DOMAIN,
+            context={"source": config_entries.SOURCE_USER},
+            data={CONF_USERNAME: "user", CONF_PASSWORD: "password"},
+        )
+        await hass.async_block_till_done()
+
+    assert result["type"] == RESULT_TYPE_FORM
+    assert result["errors"] == {"username": "invalid_auth"}
+
+
+@pytest.mark.parametrize("get_grid_region", [AsyncMock(side_effect=Exception)])
+async def test_step_user_unknown_error(hass: HomeAssistant, client_login) -> None:
+    """Test that an unknown error during the login step is handled."""
+    await setup.async_setup_component(hass, "persistent_notification", {})
+    with patch(
+        "homeassistant.components.watttime.config_flow.Client.async_login",
+        AsyncMock(side_effect=Exception),
+    ):
+        result = await hass.config_entries.flow.async_init(
+            DOMAIN,
+            context={"source": config_entries.SOURCE_USER},
+            data={CONF_USERNAME: "user", CONF_PASSWORD: "password"},
+        )
+        await hass.async_block_till_done()
+
+    assert result["type"] == RESULT_TYPE_FORM
+    assert result["errors"] == {"base": "unknown"}