diff -uprN original/ns-3-allinone/ns-3-dev/src/energy/model/simple-device-energy-model.cc modified/ns-3-allinone/ns-3-dev/src/energy/model/simple-device-energy-model.cc
--- original/ns-3-allinone/ns-3-dev/src/energy/model/simple-device-energy-model.cc	2017-03-21 19:25:39.215674363 +0530
+++ modified/ns-3-allinone/ns-3-dev/src/energy/model/simple-device-energy-model.cc	2017-03-22 00:13:58.604155000 +0530
@@ -85,6 +85,18 @@ double
 SimpleDeviceEnergyModel::GetTotalEnergyConsumption (void) const
 {
   NS_LOG_FUNCTION (this);
+  double current = GetCurrentA();
+  Time duration = Simulator::Now () - m_lastUpdateTime;
+
+  double energyToDecrease = 0.0;
+  double supplyVoltage = m_source->GetSupplyVoltage ();
+  energyToDecrease = duration.GetSeconds () * current * supplyVoltage;
+  
+  // update total energy consumption
+  m_totalEnergyConsumption += energyToDecrease;
+  // update last update time stamp
+  m_lastUpdateTime = Simulator::Now ();
+  
   return m_totalEnergyConsumption;
 }
 
diff -uprN original/ns-3-allinone/ns-3-dev/src/energy/model/simple-device-energy-model.h modified/ns-3-allinone/ns-3-dev/src/energy/model/simple-device-energy-model.h
--- original/ns-3-allinone/ns-3-dev/src/energy/model/simple-device-energy-model.h	2017-03-21 19:25:39.215674363 +0530
+++ modified/ns-3-allinone/ns-3-dev/src/energy/model/simple-device-energy-model.h	2017-03-22 00:12:52.925381000 +0530
@@ -119,11 +119,11 @@ private:
    */
   virtual double DoGetCurrentA (void) const;
 
-  Time m_lastUpdateTime;
+  mutable Time m_lastUpdateTime;
   double m_actualCurrentA;
   Ptr<EnergySource> m_source;
   Ptr<Node> m_node;
-  TracedValue<double> m_totalEnergyConsumption;
+  mutable TracedValue<double> m_totalEnergyConsumption;
 };
 
 } // namespace ns3