diff --git a/components/panasonic_heatpump/climate/__init__.py b/components/panasonic_heatpump/climate/__init__.py
index 774bebf..b4d13b8 100644
--- a/components/panasonic_heatpump/climate/__init__.py
+++ b/components/panasonic_heatpump/climate/__init__.py
@@ -13,12 +13,10 @@ from .. import (
 )
 
 CONF_COOL_MODE = "cool_mode"
-CONF_CLIMATE_TANK = "tank"
 CONF_CLIMATE_ZONE1 = "zone1"
 CONF_CLIMATE_ZONE2 = "zone2"
 
 TYPES = [
-    CONF_CLIMATE_TANK,
     CONF_CLIMATE_ZONE1,
     CONF_CLIMATE_ZONE2,
 ]
@@ -45,9 +43,6 @@ CONFIG_SCHEMA = cv.Schema(
             PanasonicHeatpumpComponent
         ),
         cv.Optional(CONF_COOL_MODE, default=False): cv.boolean,
-        cv.Optional(CONF_CLIMATE_TANK): climate.climate_schema(
-            PanasonicHeatpumpClimate
-        ).extend(climate_options(20.0, 65.0, 0.5)),
         cv.Optional(CONF_CLIMATE_ZONE1): climate.climate_schema(
             PanasonicHeatpumpClimate
         ).extend(climate_options(-5.0, 5.0, 0.5)),
diff --git a/components/panasonic_heatpump/climate/panasonic_heatpump_climate.cpp b/components/panasonic_heatpump/climate/panasonic_heatpump_climate.cpp
index 8f29efa..b313413 100644
--- a/components/panasonic_heatpump/climate/panasonic_heatpump_climate.cpp
+++ b/components/panasonic_heatpump/climate/panasonic_heatpump_climate.cpp
@@ -42,9 +42,6 @@ void PanasonicHeatpumpClimate::control(const climate::ClimateCall& call) {
   if (call.get_target_temperature().has_value()) {
     float new_temp = *call.get_target_temperature();
     switch (this->id_) {
-    case ClimateIds::CONF_CLIMATE_TANK:
-      this->parent_->set_command_byte(PanasonicCommand::setPlus128(new_temp), 42);  // set11
-      break;
     case ClimateIds::CONF_CLIMATE_ZONE1:
       this->parent_->set_command_byte(PanasonicCommand::setPlus128(new_temp), 38);  // set5
       break;
@@ -97,10 +94,6 @@ void PanasonicHeatpumpClimate::publish_new_state(const std::vector<uint8_t>& dat
 
   new_mode = this->getClimateMode(data[6]);  // set9
   switch (this->id_) {
-  case ClimateIds::CONF_CLIMATE_TANK:
-    new_target_temp_heat = PanasonicDecode::getByteMinus128(data[42]);  // set11
-    new_current_temp = PanasonicDecode::getByteMinus128(data[141]);     // top10
-    break;
   case ClimateIds::CONF_CLIMATE_ZONE1:
     new_target_temp_heat = PanasonicDecode::getByteMinus128(data[38]);  // set5
     new_target_temp_cool = PanasonicDecode::getByteMinus128(data[39]);  // set6
@@ -124,9 +117,8 @@ void PanasonicHeatpumpClimate::publish_new_state(const std::vector<uint8_t>& dat
       this->target_temperature_low == new_target_temp_cool && this->current_temperature == new_current_temp)
     return;
 
-  if (new_mode != 255)
+  if (new_mode != 0xFF)
     this->mode = (climate::ClimateMode)new_mode;
-  // this->action = climate::CLIMATE_ACTION_IDLE;
   if (this->get_traits().has_feature_flags(climate::CLIMATE_REQUIRES_TWO_POINT_TARGET_TEMPERATURE)) {
     this->target_temperature_high = new_target_temp_heat;
     this->target_temperature_low = new_target_temp_cool;
@@ -139,15 +131,6 @@ void PanasonicHeatpumpClimate::publish_new_state(const std::vector<uint8_t>& dat
 
 uint8_t PanasonicHeatpumpClimate::getClimateMode(const uint8_t input) {
   switch (this->id_) {
-  case ClimateIds::CONF_CLIMATE_TANK:
-    switch ((uint8_t)(input & 0b110000)) {
-    case 0b010000:
-      return climate::CLIMATE_MODE_OFF;
-    case 0b100000:
-      return climate::CLIMATE_MODE_HEAT;
-    default:
-      return 255;
-    };
   case ClimateIds::CONF_CLIMATE_ZONE1:
   case ClimateIds::CONF_CLIMATE_ZONE2:
     switch ((uint8_t)(input & 0b1111)) {
@@ -164,26 +147,16 @@ uint8_t PanasonicHeatpumpClimate::getClimateMode(const uint8_t input) {
     case 0b1010:
       return climate::CLIMATE_MODE_AUTO;  // 0x1A = auto-cool
     default:
-      return 255;
+      return 0xFF;
     };
   default:
-    return 255;
+    return 0xFF;
   };
 }
 
 uint8_t PanasonicHeatpumpClimate::setClimateMode(const climate::ClimateMode mode, uint8_t byte) {
   uint8_t newByte = byte;
   switch (this->id_) {
-  case ClimateIds::CONF_CLIMATE_TANK:
-    newByte = newByte & 0b11001111;
-    switch (mode) {
-    case climate::CLIMATE_MODE_OFF:
-      return newByte + 0b010000;
-    case climate::CLIMATE_MODE_HEAT:
-      return newByte + 0b100000;
-    default:
-      return 0;
-    };
   case ClimateIds::CONF_CLIMATE_ZONE1:
   case ClimateIds::CONF_CLIMATE_ZONE2:
     newByte = newByte & 0b11110000;
diff --git a/components/panasonic_heatpump/climate/panasonic_heatpump_climate.h b/components/panasonic_heatpump/climate/panasonic_heatpump_climate.h
index 5c505e3..eed84c8 100644
--- a/components/panasonic_heatpump/climate/panasonic_heatpump_climate.h
+++ b/components/panasonic_heatpump/climate/panasonic_heatpump_climate.h
@@ -9,7 +9,6 @@
 namespace esphome {
 namespace panasonic_heatpump {
 enum ClimateIds : uint8_t {
-  CONF_CLIMATE_TANK,
   CONF_CLIMATE_ZONE1,
   CONF_CLIMATE_ZONE2,
 };
diff --git a/components/panasonic_heatpump/commands.cpp b/components/panasonic_heatpump/commands.cpp
index 7a95e75..872f6c5 100644
--- a/components/panasonic_heatpump/commands.cpp
+++ b/components/panasonic_heatpump/commands.cpp
@@ -99,7 +99,7 @@ uint8_t PanasonicCommand::setOperationMode(size_t input) {
   }
 }
 
-// start of optional pcb commands
+// --- start of optional pcb commands ---
 
 uint8_t PanasonicCommand::temp2hex(float temp) {
   int hextemp = 0;
diff --git a/components/panasonic_heatpump/panasonic_heatpump.cpp b/components/panasonic_heatpump/panasonic_heatpump.cpp
index d450643..5cc16f4 100644
--- a/components/panasonic_heatpump/panasonic_heatpump.cpp
+++ b/components/panasonic_heatpump/panasonic_heatpump.cpp
@@ -93,7 +93,13 @@ void PanasonicHeatpumpComponent::loop() {
     for (auto* entity : this->climates_) {
       entity->publish_new_state(this->heatpump_default_message_);
     }
-    this->loop_state_ = LoopState::SEND_REQUEST;
+    this->loop_state_ = LoopState::PUBLISH_WATER_HEATER;
+    break;
+  case LoopState::PUBLISH_WATER_HEATER:
+    for (auto* entity : this->water_heaters_) {
+      entity->publish_new_state(this->heatpump_default_message_);
+    }
+    this->loop_state_ = LoopState::PUBLISH_EXTRA_SENSOR;
     break;
   case LoopState::PUBLISH_EXTRA_SENSOR:
     for (auto* entity : this->extra_sensors_) {
diff --git a/components/panasonic_heatpump/panasonic_heatpump.h b/components/panasonic_heatpump/panasonic_heatpump.h
index 5ae9693..fc20c1f 100644
--- a/components/panasonic_heatpump/panasonic_heatpump.h
+++ b/components/panasonic_heatpump/panasonic_heatpump.h
@@ -27,6 +27,7 @@ enum LoopState : uint8_t {
   PUBLISH_SELECT,
   PUBLISH_SWITCH,
   PUBLISH_CLIMATE,
+  PUBLISH_WATER_HEATER,
   PUBLISH_EXTRA_SENSOR,
   SEND_REQUEST,
   READ_REQUEST,
@@ -95,6 +96,9 @@ class PanasonicHeatpumpComponent : public PollingComponent, public uart::UARTDev
   void add_climate(PanasonicHeatpumpEntity* climate) {
     climates_.push_back(climate);
   }
+  void add_water_heater(PanasonicHeatpumpEntity* water_heater) {
+    water_heaters_.push_back(water_heater);
+  }
   void add_number(PanasonicHeatpumpEntity* number) {
     numbers_.push_back(number);
   }
@@ -143,6 +147,7 @@ class PanasonicHeatpumpComponent : public PollingComponent, public uart::UARTDev
   // entity vectors
   std::vector<PanasonicHeatpumpEntity*> binary_sensors_;
   std::vector<PanasonicHeatpumpEntity*> climates_;
+  std::vector<PanasonicHeatpumpEntity*> water_heaters_;
   std::vector<PanasonicHeatpumpEntity*> numbers_;
   std::vector<PanasonicHeatpumpEntity*> selects_;
   std::vector<PanasonicHeatpumpEntity*> sensors_;
diff --git a/components/panasonic_heatpump/water_heater/__init__.py b/components/panasonic_heatpump/water_heater/__init__.py
new file mode 100644
index 0000000..5d893c0
--- /dev/null
+++ b/components/panasonic_heatpump/water_heater/__init__.py
@@ -0,0 +1,60 @@
+import esphome.codegen as cg
+import esphome.config_validation as cv
+from esphome.components import water_heater
+from esphome.const import (
+    CONF_MIN_TEMPERATURE,
+    CONF_MAX_TEMPERATURE,
+)
+from .. import (
+    CONF_PANASONIC_HEATPUMP_ID,
+    PanasonicHeatpumpComponent,
+    panasonic_heatpump_ns,
+)
+
+CONF_TARGET_TEMPERATURE_STEP = "target_temperature_step"
+
+CONF_TANK = "tank"
+
+TYPES = [
+    CONF_TANK,
+]
+
+
+def water_heater_options(min_temp, max_temp, temp_step) -> cv.Schema:
+    schema = cv.Schema(
+        {
+            cv.Optional(CONF_MIN_TEMPERATURE, default=min_temp): cv.float_,
+            cv.Optional(CONF_MAX_TEMPERATURE, default=max_temp): cv.float_,
+            cv.Optional(CONF_TARGET_TEMPERATURE_STEP, default=temp_step): cv.float_,
+        }
+    )
+    return schema
+
+
+PanasonicHeatpumpWaterHeater = panasonic_heatpump_ns.class_(
+    "PanasonicHeatpumpWaterHeater", water_heater.WaterHeater, cg.Component
+)
+
+CONFIG_SCHEMA = cv.Schema(
+    {
+        cv.GenerateID(CONF_PANASONIC_HEATPUMP_ID): cv.use_id(
+            PanasonicHeatpumpComponent
+        ),
+        cv.Optional(CONF_TANK): water_heater.water_heater_schema(
+            PanasonicHeatpumpWaterHeater
+        ).extend(water_heater_options(20.0, 65.0, 0.5)),
+    }
+).extend(cv.COMPONENT_SCHEMA)
+
+
+async def to_code(config):
+    parent = await cg.get_variable(config[CONF_PANASONIC_HEATPUMP_ID])
+    for index, key in enumerate(TYPES):
+        if child_config := config.get(key):
+            var = await water_heater.new_water_heater(child_config)
+            cg.add(var.set_parent(parent))
+            cg.add(var.set_id(index))
+            cg.add(var.set_min_temperature(child_config[CONF_MIN_TEMPERATURE]))
+            cg.add(var.set_max_temperature(child_config[CONF_MAX_TEMPERATURE]))
+            cg.add(var.set_temperature_step(child_config[CONF_TARGET_TEMPERATURE_STEP]))
+            cg.add(parent.add_water_heater(var))
diff --git a/components/panasonic_heatpump/water_heater/panasonic_heatpump_water_heater.cpp b/components/panasonic_heatpump/water_heater/panasonic_heatpump_water_heater.cpp
new file mode 100644
index 0000000..c0b8585
--- /dev/null
+++ b/components/panasonic_heatpump/water_heater/panasonic_heatpump_water_heater.cpp
@@ -0,0 +1,116 @@
+#include "panasonic_heatpump_water_heater.h"
+#include "esphome/core/log.h"
+
+namespace esphome {
+namespace panasonic_heatpump {
+static const char* const TAG = "panasonic_heatpump.water_heater";
+
+void PanasonicHeatpumpWaterHeater::dump_config() {
+  LOG_WATER_HEATER("", "Panasonic Heatpump Water Heater", this);
+}
+
+water_heater::WaterHeaterTraits PanasonicHeatpumpWaterHeater::traits() {
+  auto traits = water_heater::WaterHeaterTraits();
+
+  traits.add_feature_flags(water_heater::WATER_HEATER_SUPPORTS_CURRENT_TEMPERATURE);
+  traits.set_supported_modes({water_heater::WATER_HEATER_MODE_OFF, water_heater::WATER_HEATER_MODE_HEAT_PUMP});
+  traits.set_min_temperature(this->min_temperature_);
+  traits.set_max_temperature(this->max_temperature_);
+  traits.set_target_temperature_step(this->temperature_step_);
+
+  return traits;
+}
+
+void PanasonicHeatpumpWaterHeater::control(const water_heater::WaterHeaterCall& call) {
+  if (call.get_mode().has_value()) {
+    int byte6 = this->parent_->getResponseByte(6);
+    if (byte6 >= 0) {
+      water_heater::WaterHeaterMode new_mode = *call.get_mode();
+      uint8_t newByte6 = this->setWaterHeaterMode(new_mode, (uint8_t)byte6);
+      this->parent_->set_command_byte(newByte6, 6);
+    }
+  }
+
+  float new_temp = call.get_target_temperature();
+  switch (this->id_) {
+  case WaterHeaterIds::CONF_TANK:
+    this->parent_->set_command_byte(PanasonicCommand::setPlus128(new_temp), 42);  // set11
+    break;
+  };
+
+  this->publish_state();
+  this->keep_state_ = 2;
+}
+
+void PanasonicHeatpumpWaterHeater::publish_new_state(const std::vector<uint8_t>& data) {
+  if (this->keep_state_ > 0) {
+    this->keep_state_--;
+    return;
+  }
+  if (data.empty())
+    return;
+
+  uint8_t new_mode;
+  float new_target_temp_heat;
+  float new_current_temp;
+
+  new_mode = this->getWaterHeaterMode(data[6]);  // set9
+  switch (this->id_) {
+  case WaterHeaterIds::CONF_TANK:
+    new_target_temp_heat = PanasonicDecode::getByteMinus128(data[42]);  // set11
+    new_current_temp = PanasonicDecode::getByteMinus128(data[141]);     // top10
+    break;
+  default:
+    return;
+  };
+
+  if (this->mode_ == new_mode && this->target_temperature_ == new_target_temp_heat &&
+      this->current_temperature_ == new_current_temp)
+    return;
+
+  if (new_mode != 0xFF)
+    this->mode_ = (water_heater::WaterHeaterMode)new_mode;
+  this->target_temperature_ = new_target_temp_heat;
+  this->current_temperature_ = new_current_temp;
+  this->publish_state();
+}
+
+uint8_t PanasonicHeatpumpWaterHeater::getWaterHeaterMode(const uint8_t input) {
+  switch (this->id_) {
+  case WaterHeaterIds::CONF_TANK:
+    switch ((uint8_t)(input & 0b110000)) {
+    case 0b010000:
+      return water_heater::WATER_HEATER_MODE_OFF;
+    case 0b100000:
+      return water_heater::WATER_HEATER_MODE_HEAT_PUMP;
+    default:
+      return 0xFF;
+    };
+  default:
+    return 0xFF;
+  };
+}
+
+uint8_t PanasonicHeatpumpWaterHeater::setWaterHeaterMode(const water_heater::WaterHeaterMode mode, const uint8_t byte) {
+  uint8_t newByte = byte;
+  switch (this->id_) {
+  case WaterHeaterIds::CONF_TANK:
+    newByte = newByte & 0b11001111;
+    switch (mode) {
+    case water_heater::WATER_HEATER_MODE_OFF:
+      return newByte + 0b010000;
+    case water_heater::WATER_HEATER_MODE_HEAT_PUMP:
+      return newByte + 0b100000;
+    default:
+      return 0;
+    };
+  default:
+    return 0;
+  };
+}
+
+water_heater::WaterHeaterCallInternal PanasonicHeatpumpWaterHeater::make_call() {
+  return water_heater::WaterHeaterCallInternal(this);
+}
+}  // namespace panasonic_heatpump
+}  // namespace esphome
diff --git a/components/panasonic_heatpump/water_heater/panasonic_heatpump_water_heater.h b/components/panasonic_heatpump/water_heater/panasonic_heatpump_water_heater.h
new file mode 100644
index 0000000..fe09d39
--- /dev/null
+++ b/components/panasonic_heatpump/water_heater/panasonic_heatpump_water_heater.h
@@ -0,0 +1,45 @@
+#pragma once
+#include "esphome/core/component.h"
+#include "esphome/components/water_heater/water_heater.h"
+#include "../panasonic_heatpump.h"
+#include "../decode.h"
+#include "../commands.h"
+#include <set>
+
+namespace esphome {
+namespace panasonic_heatpump {
+enum WaterHeaterIds : uint8_t {
+  CONF_TANK,
+};
+
+class PanasonicHeatpumpWaterHeater : public water_heater::WaterHeater,
+                                      public Parented<PanasonicHeatpumpComponent>,
+                                      public PanasonicHeatpumpEntity {
+ public:
+  PanasonicHeatpumpWaterHeater() = default;
+  void dump_config() override;
+  water_heater::WaterHeaterTraits traits() override;
+  void publish_new_state(const std::vector<uint8_t>& data) override;
+
+  void set_min_temperature(float value) {
+    this->min_temperature_ = value;
+  }
+  void set_max_temperature(float value) {
+    this->max_temperature_ = value;
+  }
+  void set_temperature_step(float value) {
+    this->temperature_step_ = value;
+  }
+
+ protected:
+  void control(const water_heater::WaterHeaterCall& call) override;
+  water_heater::WaterHeaterCallInternal make_call() override;
+  uint8_t getWaterHeaterMode(const uint8_t input);
+  uint8_t setWaterHeaterMode(const water_heater::WaterHeaterMode mode, const uint8_t byte);
+
+  float min_temperature_{20.0f};
+  float max_temperature_{65.0f};
+  float temperature_step_{0.5f};
+};
+}  // namespace panasonic_heatpump
+}  // namespace esphome
diff --git a/tests/panasonic_heatpump/test_panasonic_heatpump_cztaw1.yaml b/tests/panasonic_heatpump/test_panasonic_heatpump_cztaw1.yaml
index e31a4df..37d9333 100644
--- a/tests/panasonic_heatpump/test_panasonic_heatpump_cztaw1.yaml
+++ b/tests/panasonic_heatpump/test_panasonic_heatpump_cztaw1.yaml
@@ -82,6 +82,12 @@ switch:
 
 # Test climate controls - first item only
 climate:
+  - platform: panasonic_heatpump
+    zone1:
+      name: "Zone 1"
+
+# Test water_heater controls - first item only
+water_heater:
   - platform: panasonic_heatpump
     tank:
       name: "DHW"
diff --git a/tests/panasonic_heatpump/test_panasonic_heatpump_esp32c3.yaml b/tests/panasonic_heatpump/test_panasonic_heatpump_esp32c3.yaml
index bf48523..1b08fa5 100644
--- a/tests/panasonic_heatpump/test_panasonic_heatpump_esp32c3.yaml
+++ b/tests/panasonic_heatpump/test_panasonic_heatpump_esp32c3.yaml
@@ -73,6 +73,12 @@ switch:
 
 # Test climate controls - first item only
 climate:
+  - platform: panasonic_heatpump
+    zone1:
+      name: "Zone 1"
+
+# Test water_heater controls - first item only
+water_heater:
   - platform: panasonic_heatpump
     tank:
       name: "DHW"
diff --git a/tests/panasonic_heatpump/test_panasonic_heatpump_esp32s2.yaml b/tests/panasonic_heatpump/test_panasonic_heatpump_esp32s2.yaml
index 2959dad..979dd0b 100644
--- a/tests/panasonic_heatpump/test_panasonic_heatpump_esp32s2.yaml
+++ b/tests/panasonic_heatpump/test_panasonic_heatpump_esp32s2.yaml
@@ -73,6 +73,12 @@ switch:
 
 # Test climate controls - first item only
 climate:
+  - platform: panasonic_heatpump
+    zone1:
+      name: "Zone 1"
+
+# Test water_heater controls - first item only
+water_heater:
   - platform: panasonic_heatpump
     tank:
       name: "DHW"
diff --git a/tests/panasonic_heatpump/test_panasonic_heatpump_esp8266.yaml b/tests/panasonic_heatpump/test_panasonic_heatpump_esp8266.yaml
index 5abdd2d..39edccd 100644
--- a/tests/panasonic_heatpump/test_panasonic_heatpump_esp8266.yaml
+++ b/tests/panasonic_heatpump/test_panasonic_heatpump_esp8266.yaml
@@ -70,6 +70,12 @@ switch:
 
 # Test climate controls - first item only
 climate:
+  - platform: panasonic_heatpump
+    zone1:
+      name: "Zone 1"
+
+# Test water_heater controls - first item only
+water_heater:
   - platform: panasonic_heatpump
     tank:
       name: "DHW"
diff --git a/tests/panasonic_heatpump/test_panasonic_heatpump_full.yaml b/tests/panasonic_heatpump/test_panasonic_heatpump_full.yaml
index 32404ae..6aa062a 100644
--- a/tests/panasonic_heatpump/test_panasonic_heatpump_full.yaml
+++ b/tests/panasonic_heatpump/test_panasonic_heatpump_full.yaml
@@ -472,9 +472,13 @@ switch:
 climate:
   - platform: panasonic_heatpump
     cool_mode: true
+    zone1:
+      name: "Zone 1"
+    zone2:
+      name: "Zone 2"
+
+# Test water_heater platform
+water_heater:
+  - platform: panasonic_heatpump
     tank:
       name: "DHW"
-    zone1:
-      name: "Zone1"
-    zone2:
-      name: "Zone2"
diff --git a/tests/panasonic_heatpump/test_panasonic_heatpump_unit.py b/tests/panasonic_heatpump/test_panasonic_heatpump_unit.py
index 0c812ef..a584887 100644
--- a/tests/panasonic_heatpump/test_panasonic_heatpump_unit.py
+++ b/tests/panasonic_heatpump/test_panasonic_heatpump_unit.py
@@ -325,6 +325,86 @@ class TestPanasonicHeatpumpPlatforms:
         except ImportError:
             pytest.skip("Climate platform not accessible in test environment")
 
+    def test_water_heater_platform_exists(self):
+        """Test that water_heater platform can be imported."""
+        try:
+            import sys
+            import os
+
+            components_path = os.path.join(
+                os.path.dirname(__file__), "..", "..", "components"
+            )
+            sys.path.insert(0, components_path)
+
+            from panasonic_heatpump.water_heater import __init__ as wh_init
+
+            assert wh_init is not None
+        except ImportError:
+            pytest.skip("Water heater platform not accessible in test environment")
+
+    def test_water_heater_platform_metadata(self):
+        """Test that water_heater platform has correct configuration."""
+        try:
+            import sys
+            import os
+
+            components_path = os.path.join(
+                os.path.dirname(__file__), "..", "..", "components"
+            )
+            sys.path.insert(0, components_path)
+
+            from panasonic_heatpump.water_heater import (
+                CONFIG_SCHEMA,
+                CONF_TANK,
+                TYPES,
+            )
+
+            assert CONFIG_SCHEMA is not None
+            assert CONF_TANK == "tank"
+            assert CONF_TANK in TYPES
+        except ImportError:
+            pytest.skip("Water heater platform not accessible in test environment")
+
+    def test_water_heater_platform_options(self):
+        """Test that water_heater_options schema is defined."""
+        try:
+            import sys
+            import os
+
+            components_path = os.path.join(
+                os.path.dirname(__file__), "..", "..", "components"
+            )
+            sys.path.insert(0, components_path)
+
+            from panasonic_heatpump.water_heater import water_heater_options
+
+            # Test default temperature range and step
+            schema = water_heater_options(20.0, 65.0, 0.5)
+            assert schema is not None
+
+            # Verify defaults work
+            schema2 = water_heater_options(15.0, 70.0, 1.0)
+            assert schema2 is not None
+        except ImportError:
+            pytest.skip("Water heater platform not accessible in test environment")
+
+    def test_water_heater_to_code_function(self):
+        """Test that water_heater to_code function is defined."""
+        try:
+            import sys
+            import os
+
+            components_path = os.path.join(
+                os.path.dirname(__file__), "..", "..", "components"
+            )
+            sys.path.insert(0, components_path)
+
+            from panasonic_heatpump.water_heater import to_code
+
+            assert callable(to_code)
+        except ImportError:
+            pytest.skip("Water heater platform not accessible in test environment")
+
 
 class TestPanasonicHeatpumpCodeGeneration:
     """Test suite for code generation logic."""