diff --git a/src/main/scala/edu/ie3/simona/model/thermal/ThermalGrid.scala b/src/main/scala/edu/ie3/simona/model/thermal/ThermalGrid.scala
index 249699c7f5..6f6656c9ad 100644
--- a/src/main/scala/edu/ie3/simona/model/thermal/ThermalGrid.scala
+++ b/src/main/scala/edu/ie3/simona/model/thermal/ThermalGrid.scala
@@ -40,6 +40,7 @@ import scala.jdk.CollectionConverters.SetHasAsScala
 final case class ThermalGrid(
     house: Option[ThermalHouse],
     storage: Option[ThermalStorage],
+    domesticHotWaterStorage: Option[ThermalStorage],
 ) extends LazyLogging {
 
   /** Determine the energy demand of the total grid at the given instance in
@@ -76,7 +77,7 @@ final case class ThermalGrid(
             house
               .zip(state.houseState)
               .map { case (house, state) =>
-                house.energyDemand(
+                house.energyDemandHeating(
                   tick,
                   ambientTemperature,
                   state,
@@ -131,6 +132,54 @@ final case class ThermalGrid(
     )
   }
 
+  /** Determines if the domestic hot water storage has energy demand or not.
+    *
+    * @param tick
+    *   Questionable tick
+    * @param state
+    *   most recent state, that is valid for this model
+    * @return
+    *   the needed energy for heating in the questioned tick
+    */
+
+  def energyDemandDomesticHotWaterStorage(
+      tick: Long,
+      state: ThermalGridState,
+  ): ThermalEnergyDemand = {
+
+    val domesticHotWaterStorageDemand = {
+      domesticHotWaterStorage
+        .zip(state.domesticHotWaterStorageState)
+        .map { case (hotWaterStorage, state) =>
+          val updatedhotWaterStorageState =
+            hotWaterStorage.updateState(tick, state.qDot, state)._1
+          val storedEnergy = updatedhotWaterStorageState.storedEnergy
+          val soc = storedEnergy / hotWaterStorage.getMaxEnergyThreshold
+          val hotWaterStorageRequired =
+            if (soc < 0.5) {
+              hotWaterStorage.getMaxEnergyThreshold * 0.5 - storedEnergy
+            } else {
+              zeroMWH
+            }
+
+          val hotWaterStoragePossible =
+            hotWaterStorage.getMaxEnergyThreshold - storedEnergy
+          ThermalEnergyDemand(
+            hotWaterStorageRequired,
+            hotWaterStoragePossible,
+          )
+        }
+        .getOrElse(
+          ThermalEnergyDemand(zeroMWH, zeroMWH)
+        )
+    }
+
+    ThermalEnergyDemand(
+      domesticHotWaterStorageDemand.required,
+      domesticHotWaterStorageDemand.possible,
+    )
+  }
+
   /** Update the current state of the grid
     *
     * @param tick
@@ -196,12 +245,25 @@ final case class ThermalGrid(
     // TODO: We would need to issue a storage result model here...
 
     /* Consider the action in the last state */
-    val (qDotHouseLastState, qDotStorageLastState) = state match {
-      case ThermalGridState(Some(houseState), Some(storageState)) =>
-        (houseState.qDot, storageState.qDot)
-      case ThermalGridState(Some(houseState), None) => (houseState.qDot, zeroKW)
-      case ThermalGridState(None, Some(storageState)) =>
-        (zeroKW, storageState.qDot)
+    val (
+      qDotHouseLastState,
+      qDotStorageLastState,
+      qDotDomesticWaterStorageLastState,
+    ) = state match {
+      case ThermalGridState(
+            Some(houseState),
+            Some(storageState),
+            Some(domesticWaterState),
+          ) =>
+        (houseState.qDot, storageState.qDot, domesticWaterState.qDot)
+      case ThermalGridState(Some(houseState), Some(storageState), None) =>
+        (houseState.qDot, storageState.qDot, zeroKW)
+      case ThermalGridState(Some(houseState), None, Some(domesticWaterState)) =>
+        (houseState.qDot, zeroKW, domesticWaterState.qDot)
+      case ThermalGridState(Some(houseState), None, None) =>
+        (houseState.qDot, zeroKW, zeroKW)
+      case ThermalGridState(None, Some(storageState), None) =>
+        (zeroKW, storageState.qDot, zeroKW)
       case _ =>
         throw new InconsistentStateException(
           "There should be at least a house or a storage state."
@@ -608,9 +670,23 @@ object ThermalGrid {
         case _ => None
       }
       .toSet
+    val domesticHotWaterStorage: Set[ThermalStorage] = input
+      .storages()
+      .asScala
+      .flatMap {
+
+        // FIXME
+        //        case domesticHotWaterInput: DomesticHotWaterStorageInput =>
+        //        Some(DomesticHotWaterStorageInput(domesticHotWaterInput))
+        case cylindricalInput: CylindricalStorageInput =>
+          Some(CylindricalThermalStorage(cylindricalInput))
+        case _ => None
+      }
+      .toSet
     new ThermalGrid(
       houses.headOption,
       storages.headOption,
+      domesticHotWaterStorage.headOption,
     )
   }
 
@@ -623,12 +699,14 @@ object ThermalGrid {
   final case class ThermalGridState(
       houseState: Option[ThermalHouseState],
       storageState: Option[ThermalStorageState],
+      domesticHotWaterStorageState: Option[ThermalStorageState],
   )
 
   def startingState(thermalGrid: ThermalGrid): ThermalGridState =
     ThermalGridState(
       thermalGrid.house.map(house => ThermalHouse.startingState(house)),
       thermalGrid.storage.map(_.startingState),
+      thermalGrid.domesticHotWaterStorage.map(_.startingState),
     )
 
   /** Defines the thermal energy demand of a thermal grid. It comprises the
diff --git a/src/main/scala/edu/ie3/simona/model/thermal/ThermalHouse.scala b/src/main/scala/edu/ie3/simona/model/thermal/ThermalHouse.scala
index c08a6a3114..31f86bb98f 100644
--- a/src/main/scala/edu/ie3/simona/model/thermal/ThermalHouse.scala
+++ b/src/main/scala/edu/ie3/simona/model/thermal/ThermalHouse.scala
@@ -25,12 +25,15 @@ import edu.ie3.util.quantities.PowerSystemUnits
 import edu.ie3.util.scala.quantities.DefaultQuantities._
 import edu.ie3.util.scala.quantities.{ThermalConductance, WattsPerKelvin}
 import squants.energy.KilowattHours
-import squants.thermal.{Kelvin, ThermalCapacity}
+import squants.space.Litres
+import squants.thermal.{Celsius, Kelvin, ThermalCapacity}
 import squants.time.{Hours, Seconds}
-import squants.{Energy, Power, Temperature, Time}
+import squants.{Energy, Power, Temperature, Time, Volume}
 import tech.units.indriya.unit.Units
 
+import java.time.ZonedDateTime
 import java.util.UUID
+import java.time.Duration
 
 /** A thermal house model
   *
@@ -74,10 +77,10 @@ final case class ThermalHouse(
       bus,
     ) {
 
-  /** Calculate the energy demand at the instance in question. If the inner
-    * temperature is at or above the lower boundary temperature, there is no
-    * demand. If it is below the target temperature, the demand is the energy
-    * needed to heat up the house to the maximum temperature. The current
+  /** Calculate the energy demand for heating at the instance in question. If
+    * the inner temperature is at or above the lower boundary temperature, there
+    * is no demand. If it is below the target temperature, the demand is the
+    * energy needed to heat up the house to the maximum temperature. The current
     * (external) thermal infeed is not accounted for, as we assume, that after
     * determining the thermal demand, a change in external infeed will take
     * place.
@@ -89,9 +92,9 @@ final case class ThermalHouse(
     * @param state
     *   most recent state, that is valid for this model
     * @return
-    *   the needed energy in the questioned tick
+    *   the needed energy for heating in the questioned tick
     */
-  def energyDemand(
+  def energyDemandHeating(
       tick: Long,
       ambientTemperature: Temperature,
       state: ThermalHouseState,
@@ -135,6 +138,158 @@ final case class ThermalHouse(
     ThermalEnergyDemand(requiredEnergy, possibleEnergy)
   }
 
+  /** Calculate the energy demand for warm water at the instance in question.
+    *
+    * @param tick
+    *   Questionable tick
+    * @param state
+    *   most recent state, that is valid for this model
+    * @return
+    *   the needed energy for heating in the questioned tick
+    */
+
+  def energyDemandWater(
+      tick: Long,
+      state: ThermalHouseState,
+      simulationStart: ZonedDateTime,
+  ): ThermalEnergyDemand = {
+
+    // Fixme:
+    val noPersonsInHoushold = 2
+
+    val lastStateTime: ZonedDateTime = simulationStart.plusSeconds(state.tick)
+    val actualStateTime: ZonedDateTime = simulationStart.plusSeconds(tick)
+    val timeDiff: Duration = Duration.between(lastStateTime, actualStateTime)
+
+    // if we have been triggered this hour there the water Demand is already covered
+    if (timeDiff.toSeconds > 3600) {
+
+      // FIXME
+      // the lastStates hour is already considered. Need to start lastState.getHour + 1 until tick.getHour
+
+      ThermalEnergyDemand(zeroKWH, zeroKWH)
+    } else if (actualStateTime.getHour != lastStateTime.getHour) {
+      // determine demand for the actual hour
+
+      val waterDemand =
+        waterDemandOfHour(tick, noPersonsInHoushold, simulationStart)
+
+      val thermalDemandWater: Energy =
+        thermalEnergyDemandWater(waterDemand, Celsius(10d), Celsius(55d))
+      ThermalEnergyDemand(thermalDemandWater, thermalDemandWater)
+
+    } else ThermalEnergyDemand(zeroKWH, zeroKWH)
+
+  }
+
+  /** Calculate the energy required to heat up a given volume of water from a
+    * start to an end temperature
+    *
+    * @param waterDemand
+    *   water volume to get heated up
+    * @param startTemperature
+    *   starting Temperature
+    * @param endTemperature
+    *   end Temperature
+    * @return
+    *   the needed energy
+    */
+
+  private def thermalEnergyDemandWater(
+      waterDemand: Volume,
+      startTemperature: Temperature,
+      endTemperature: Temperature,
+  ): Energy = {
+    if (endTemperature < startTemperature)
+      throw new RuntimeException(
+        s"End temperature of $endTemperature is lower than the start temperature $startTemperature for the water heating system"
+      )
+
+    waterDemand.toLitres * KilowattHours(
+      1.16
+    ) * (endTemperature.toCelsiusDegrees - startTemperature.toCelsiusDegrees)
+  }
+
+  def waterDemandOfHour(
+      tick: Long,
+      noPersonsInHoushold: Int,
+      simulationStart: ZonedDateTime,
+  ): Volume = {
+
+    // Volume => VDI 2067 Blatt 12
+    // Time series relative => DIN EN 12831-3 Table B.2 for single family houses and for flats
+    val waterVolumeRelativeHouse: Map[Int, Double] = Map(
+      0 -> 0.018,
+      1 -> 0.01,
+      2 -> 0.006,
+      3 -> 0.003,
+      4 -> 0.004,
+      5 -> 0.006,
+      6 -> 0.024,
+      7 -> 0.047,
+      8 -> 0.068,
+      9 -> 0.057,
+      10 -> 0.061,
+      11 -> 0.061,
+      12 -> 0.063,
+      13 -> 0.064,
+      14 -> 0.051,
+      15 -> 0.044,
+      16 -> 0.043,
+      17 -> 0.047,
+      18 -> 0.057,
+      19 -> 0.065,
+      20 -> 0.066,
+      21 -> 0.058,
+      22 -> 0.045,
+      23 -> 0.031,
+    )
+    val waterVolumeRelativeFlat: Map[Int, Double] = Map(
+      0 -> 0.01,
+      1 -> 0.01,
+      2 -> 0.01,
+      3 -> 0.0,
+      4 -> 0.0,
+      5 -> 0.1,
+      6 -> 0.03,
+      7 -> 0.06,
+      8 -> 0.08,
+      9 -> 0.06,
+      10 -> 0.05,
+      11 -> 0.05,
+      12 -> 0.06,
+      13 -> 0.06,
+      14 -> 0.05,
+      15 -> 0.04,
+      16 -> 0.04,
+      17 -> 0.05,
+      18 -> 0.06,
+      19 -> 0.07,
+      20 -> 0.07,
+      21 -> 0.06,
+      22 -> 0.05,
+      23 -> 0.02,
+    )
+
+    val waterDemandVolumePerPersonYear =
+      // Shower and Bath + washbasin + dish washing per hand (also dish washer in the building)
+      Litres(8600 + 4200 + 300)
+
+    val isHouse = true
+
+    val currentHour: Int = simulationStart.plusSeconds(tick).getHour
+
+    val waterVolumeRelative: Map[Int, Double] =
+      if (isHouse) waterVolumeRelativeHouse else waterVolumeRelativeFlat
+
+    waterVolumeRelative.getOrElse(
+      currentHour,
+      throw new RuntimeException(
+        "Couldn't get the actual hour to determine water demand"
+      ),
+    ) * noPersonsInHoushold * waterDemandVolumePerPersonYear / 365
+  }
+
   /** Calculate the needed energy to change from start temperature to target
     * temperature
     *
diff --git a/src/test/scala/edu/ie3/simona/model/participant/HpModelSpec.scala b/src/test/scala/edu/ie3/simona/model/participant/HpModelSpec.scala
index 6dec2fc25c..283b2f4171 100644
--- a/src/test/scala/edu/ie3/simona/model/participant/HpModelSpec.scala
+++ b/src/test/scala/edu/ie3/simona/model/participant/HpModelSpec.scala
@@ -213,7 +213,7 @@ class HpModelSpec
                     _,
                     activePower,
                     _,
-                    ThermalGridState(Some(thermalHouseState), _),
+                    ThermalGridState(Some(thermalHouseState), _, _),
                     maybeThreshold,
                   ) =>
                 isRunning shouldBe expectedRunningState
@@ -255,6 +255,7 @@ class HpModelSpec
                 Kilowatts(0),
               )
             ),
+            None,
           )
           val lastState = HpState(
             isRunning = true,
diff --git a/src/test/scala/edu/ie3/simona/model/participant/HpModelTestData.scala b/src/test/scala/edu/ie3/simona/model/participant/HpModelTestData.scala
index cbbe51ba9e..9e846e3eb5 100644
--- a/src/test/scala/edu/ie3/simona/model/participant/HpModelTestData.scala
+++ b/src/test/scala/edu/ie3/simona/model/participant/HpModelTestData.scala
@@ -91,6 +91,7 @@ trait HpModelTestData {
     ThermalGrid(
       Some(thermalHouse),
       thermalStorage,
+      None,
     )
 
   private val thermHouseUuid: UUID =
@@ -142,6 +143,7 @@ trait HpModelTestData {
       )
     ),
     None,
+    None,
   )
 
   protected def hpData: HpRelevantData =
diff --git a/src/test/scala/edu/ie3/simona/model/thermal/ThermalGridWithHouseAndStorageSpec.scala b/src/test/scala/edu/ie3/simona/model/thermal/ThermalGridWithHouseAndStorageSpec.scala
index 34cc9f5b0e..0b756af29c 100644
--- a/src/test/scala/edu/ie3/simona/model/thermal/ThermalGridWithHouseAndStorageSpec.scala
+++ b/src/test/scala/edu/ie3/simona/model/thermal/ThermalGridWithHouseAndStorageSpec.scala
@@ -48,6 +48,7 @@ class ThermalGridWithHouseAndStorageSpec
         case ThermalGrid(
               Some(thermalHouseGenerated),
               Some(thermalStorageGenerated),
+              None,
             ) =>
           thermalHouseGenerated shouldBe thermalHouse
           thermalStorageGenerated shouldBe thermalStorage
@@ -74,6 +75,7 @@ class ThermalGridWithHouseAndStorageSpec
                 Some(
                   ThermalStorageState(storageTick, storedEnergy, qDotStorage)
                 ),
+                None,
               ) =>
             houseTick shouldBe expectedHouseStartingState.tick
             storageTick shouldBe expectedHouseStartingState.tick
@@ -160,6 +162,7 @@ class ThermalGridWithHouseAndStorageSpec
                 Some(
                   ThermalStorageState(storageTick, storedEnergy, qDotStorage)
                 ),
+                None,
               ) =>
             storageTick shouldBe 0L
             storedEnergy should approximate(initialLoading)
@@ -196,6 +199,7 @@ class ThermalGridWithHouseAndStorageSpec
                 Some(
                   ThermalStorageState(storageTick, storedEnergy, qDotStorage)
                 ),
+                None,
               ) =>
             houseTick shouldBe 0L
             innerTemperature should approximate(Celsius(18.9999d))
@@ -484,6 +488,7 @@ class ThermalGridWithHouseAndStorageSpec
                 Some(
                   ThermalStorageState(storageTick, storedEnergy, qDotStorage)
                 ),
+                None,
               ) =>
             houseTick shouldBe 0L
             innerTemperature should approximate(Celsius(18.9999d))
@@ -531,6 +536,7 @@ class ThermalGridWithHouseAndStorageSpec
                 Some(
                   ThermalStorageState(storageTick, storedEnergy, qDotStorage)
                 ),
+                None,
               ) =>
             houseTick shouldBe 0L
             innerTemperature should approximate(Celsius(20.99999167d))
diff --git a/src/test/scala/edu/ie3/simona/model/thermal/ThermalGridWithHouseOnlySpec.scala b/src/test/scala/edu/ie3/simona/model/thermal/ThermalGridWithHouseOnlySpec.scala
index 0dbe5f9625..9522039839 100644
--- a/src/test/scala/edu/ie3/simona/model/thermal/ThermalGridWithHouseOnlySpec.scala
+++ b/src/test/scala/edu/ie3/simona/model/thermal/ThermalGridWithHouseOnlySpec.scala
@@ -36,7 +36,7 @@ class ThermalGridWithHouseOnlySpec extends UnitSpec with ThermalHouseTestData {
         )
 
       ThermalGrid(thermalGridInput) match {
-        case ThermalGrid(Some(thermalHouseGenerated), None) =>
+        case ThermalGrid(Some(thermalHouseGenerated), None, None) =>
           thermalHouseGenerated shouldBe thermalHouse
         case _ =>
           fail("Generation of thermal grid from thermal input grid failed.")
@@ -59,6 +59,7 @@ class ThermalGridWithHouseOnlySpec extends UnitSpec with ThermalHouseTestData {
           case ThermalGridState(
                 Some(ThermalHouseState(tick, innerTemperature, thermalInfeed)),
                 None,
+                None,
               ) =>
             tick shouldBe expectedHouseStartingState.tick
             innerTemperature should approximate(
@@ -74,7 +75,7 @@ class ThermalGridWithHouseOnlySpec extends UnitSpec with ThermalHouseTestData {
     "determining the energy demand" should {
       "exactly be the demand of the house" in {
         val tick = 10800 // after three house
-        val expectedHouseDemand = thermalHouse.energyDemand(
+        val expectedHouseDemand = thermalHouse.energyDemandHeating(
           tick,
           testGridambientTemperature,
           expectedHouseStartingState,
@@ -116,6 +117,7 @@ class ThermalGridWithHouseOnlySpec extends UnitSpec with ThermalHouseTestData {
           case ThermalGridState(
                 Some(ThermalHouseState(tick, innerTemperature, qDot)),
                 None,
+                None,
               ) =>
             tick shouldBe 0L
             innerTemperature should approximate(Celsius(18.9999d))
@@ -143,6 +145,7 @@ class ThermalGridWithHouseOnlySpec extends UnitSpec with ThermalHouseTestData {
           case ThermalGridState(
                 Some(ThermalHouseState(tick, innerTemperature, qDot)),
                 None,
+                None,
               ) =>
             tick shouldBe 0L
             innerTemperature should approximate(Celsius(18.9999d))
@@ -179,6 +182,7 @@ class ThermalGridWithHouseOnlySpec extends UnitSpec with ThermalHouseTestData {
           case ThermalGridState(
                 Some(ThermalHouseState(tick, innerTemperature, qDot)),
                 None,
+                None,
               ) =>
             tick shouldBe 0L
             innerTemperature should approximate(Celsius(18.9999d))
@@ -205,6 +209,7 @@ class ThermalGridWithHouseOnlySpec extends UnitSpec with ThermalHouseTestData {
                 ThermalGridState(
                   Some(ThermalHouseState(tick, innerTemperature, qDot)),
                   None,
+                  None,
                 ),
                 Some(HouseTemperatureUpperBoundaryReached(thresholdTick)),
               ) =>
@@ -229,6 +234,7 @@ class ThermalGridWithHouseOnlySpec extends UnitSpec with ThermalHouseTestData {
                 ThermalGridState(
                   Some(ThermalHouseState(tick, innerTemperature, qDot)),
                   None,
+                  None,
                 ),
                 Some(HouseTemperatureLowerBoundaryReached(thresholdTick)),
               ) =>
@@ -253,6 +259,7 @@ class ThermalGridWithHouseOnlySpec extends UnitSpec with ThermalHouseTestData {
                 ThermalGridState(
                   Some(ThermalHouseState(tick, innerTemperature, qDot)),
                   None,
+                  None,
                 ),
                 Some(HouseTemperatureLowerBoundaryReached(thresholdTick)),
               ) =>
diff --git a/src/test/scala/edu/ie3/simona/model/thermal/ThermalGridWithStorageOnlySpec.scala b/src/test/scala/edu/ie3/simona/model/thermal/ThermalGridWithStorageOnlySpec.scala
index ada5195e33..1592e38c7a 100644
--- a/src/test/scala/edu/ie3/simona/model/thermal/ThermalGridWithStorageOnlySpec.scala
+++ b/src/test/scala/edu/ie3/simona/model/thermal/ThermalGridWithStorageOnlySpec.scala
@@ -41,7 +41,7 @@ class ThermalGridWithStorageOnlySpec
         )
 
       ThermalGrid(thermalGridInput) match {
-        case ThermalGrid(None, Some(thermalStorageGenerated)) =>
+        case ThermalGrid(None, Some(thermalStorageGenerated), None) =>
           thermalStorageGenerated shouldBe thermalStorage
         case _ =>
           fail("Generation of thermal grid from thermal input grid failed.")
@@ -64,6 +64,7 @@ class ThermalGridWithStorageOnlySpec
           case ThermalGridState(
                 None,
                 Some(ThermalStorageState(tick, storedEnergy, qDot)),
+                None,
               ) =>
             tick shouldBe expectedStorageStartingState.tick
             storedEnergy should approximate(
@@ -125,6 +126,7 @@ class ThermalGridWithStorageOnlySpec
           case ThermalGridState(
                 None,
                 Some(ThermalStorageState(tick, storedEnergy, qDot)),
+                None,
               ) =>
             tick shouldBe 0L
             storedEnergy should approximate(KilowattHours(430d))
@@ -159,6 +161,7 @@ class ThermalGridWithStorageOnlySpec
           case ThermalGridState(
                 None,
                 Some(ThermalStorageState(tick, storedEnergy, qDot)),
+                None,
               ) =>
             tick shouldBe 0L
             storedEnergy should approximate(KilowattHours(230d))
@@ -186,6 +189,7 @@ class ThermalGridWithStorageOnlySpec
           case ThermalGridState(
                 None,
                 Some(ThermalStorageState(tick, storedEnergy, qDot)),
+                None,
               ) =>
             tick shouldBe 0L
             storedEnergy should approximate(KilowattHours(230d))
@@ -217,6 +221,7 @@ class ThermalGridWithStorageOnlySpec
                 ThermalGridState(
                   None,
                   Some(ThermalStorageState(tick, storedEnergy, qDot)),
+                  None,
                 ),
                 Some(StorageEmpty(thresholdTick)),
               ) =>
@@ -242,6 +247,7 @@ class ThermalGridWithStorageOnlySpec
                 ThermalGridState(
                   None,
                   Some(ThermalStorageState(tick, storedEnergy, qDot)),
+                  None,
                 ),
                 None,
               ) =>