diff --git a/city_model_structure/energy_systems/water_to_water_hp.py b/city_model_structure/energy_systems/water_to_water_hp.py
index e69de29b..60a97cac 100644
--- a/city_model_structure/energy_systems/water_to_water_hp.py
+++ b/city_model_structure/energy_systems/water_to_water_hp.py
@@ -0,0 +1,151 @@
+"""
+water_to_water_hp module defines a water to water heat pump heat pump
+SPDX - License - Identifier: LGPL - 3.0 - or -later
+Copyright © 2021 Project Author Peter Yefi peteryefi@gmail.com
+"""
+
+from typing import List
+from city_model_structure.energy_systems.heat_pump import HeatPump
+
+
+class WaterToWaterHP(HeatPump):
+  """
+  WaterToWaterHP class
+  """
+
+  def __init__(self):
+    super().__init__()
+    self._entering_water_temp = None
+    self._leaving_water_temp = None
+    self._total_cooling_capacity = None
+    self._power_demand = None
+    self._flow_rate = None
+    self._total_cooling_capacity_coff = None
+    self._power_demand_coff = None
+
+  @property
+  def entering_water_temp(self) -> List[float]:
+    """
+    Get entering water temperature in degree celsius
+    :return: [[float]]
+    """
+    return self._entering_water_temp
+
+  @entering_water_temp.setter
+  def entering_water_temp(self, value):
+    """
+    Set entering water temperature in degree celsius
+    :param value: [[float]]
+    """
+    if self._entering_water_temp is None:
+      self._entering_water_temp = value
+
+  @property
+  def leaving_water_temp(self) -> List[float]:
+    """
+    Get leaving water temperature in degree celsius
+    :return: [[float]]
+    """
+    return self._leaving_water_temp
+
+  @leaving_water_temp.setter
+  def leaving_water_temp(self, value):
+    """
+    Set the leaving water temperature in degree celsius
+    :param value: [[float]]
+    :return:
+    """
+    if self._leaving_water_temp is None:
+      self._leaving_water_temp = value
+
+  @property
+  def total_cooling_capacity(self) -> List[float]:
+    """
+    Get total cooling capacity
+    :return: [float]
+    """
+    return self._total_cooling_capacity
+
+  @total_cooling_capacity.setter
+  def total_cooling_capacity(self, value):
+    """
+    Set the value for total cooling capacity
+    :param value: [float]
+    :return:
+    """
+    if self._total_cooling_capacity is None:
+      self._total_cooling_capacity = value
+
+  @property
+  def power_demand(self) -> List[float]:
+    """
+    Get power demand in kW
+    :return: [float]
+    """
+    return self._power_demand
+
+  @power_demand.setter
+  def power_demand(self, value):
+    """
+    Set the value for power demand in kW
+    :param value: [float]
+    :return:
+    """
+    if self._power_demand is None:
+      self._power_demand = value
+
+  @property
+  def flow_rate(self) -> List[float]:
+    """
+    Get flow rate in kg/s
+    :return: [[float]]
+    """
+    return self._flow_rate
+
+  @flow_rate.setter
+  def flow_rate(self, value):
+    """
+    Set flow rate in kW
+    :param value: [[float]]
+    :return:
+    """
+    if self._flow_rate is None:
+      self._flow_rate = value
+
+  @property
+  def total_cooling_capacity_coff(self) -> List[float]:
+    """
+    Get coefficients for total cooling capacity
+    :return: [[float]]
+    """
+    return self._total_cooling_capacity_coff
+
+  @total_cooling_capacity_coff.setter
+  def total_cooling_capacity_coff(self, value):
+    """
+    Set coefficients for totol cooling capacity
+    :param value: [[float]]
+    :return:
+    """
+    if self._total_cooling_capacity_coff is None:
+      self._total_cooling_capacity_coff = value
+
+  @property
+  def power_demand_coff(self) -> List[float]:
+    """
+    Get power demand coefficients
+    :return: [float]
+    """
+    return self._power_demand_coff
+
+  @power_demand_coff.setter
+  def power_demand_coff(self, value):
+    """
+    Set the value for power demand coefficients
+    :param value: [float]
+    :return:
+    """
+    if self._power_demand_coff is None:
+      self._power_demand_coff = value
+
+