diff --git a/WinNUT_V2/WinNUT-Client/My Project/Settings.settings b/WinNUT_V2/WinNUT-Client/My Project/Settings.settings
index 579c341..255d4ae 100644
--- a/WinNUT_V2/WinNUT-Client/My Project/Settings.settings	
+++ b/WinNUT_V2/WinNUT-Client/My Project/Settings.settings	
@@ -113,5 +113,11 @@
     <Setting Name="IsFirstRun" Type="System.Boolean" Scope="User">
       <Value Profile="(Default)">True</Value>
     </Setting>
+    <Setting Name="CAL_PowerFactor" Type="System.Double" Scope="User">
+      <Value Profile="(Default)">0.95</Value>
+    </Setting>
+    <Setting Name="CAL_ApparentPowerNom" Type="System.Int32" Scope="User">
+      <Value Profile="(Default)">2400</Value>
+    </Setting>
   </Settings>
 </SettingsFile>
\ No newline at end of file
diff --git a/WinNUT_V2/WinNUT-Client/Pref_Gui.Designer.vb b/WinNUT_V2/WinNUT-Client/Pref_Gui.Designer.vb
index cf76326..4e33c88 100644
--- a/WinNUT_V2/WinNUT-Client/Pref_Gui.Designer.vb
+++ b/WinNUT_V2/WinNUT-Client/Pref_Gui.Designer.vb
@@ -28,6 +28,16 @@ Partial Class Pref_Gui
         Me.Tab_Connexion = New System.Windows.Forms.TabPage()
         Me.pollingIntervalUnitLabel = New System.Windows.Forms.Label()
         Me.pollingIntervalValue = New System.Windows.Forms.NumericUpDown()
+
+        Me.Tb_Cal_PowerFactor.DecimalPlaces = 2
+        Me.Tb_Cal_PowerFactor.Minimum = New Decimal(New Integer() {200, 0, 0, 0})
+        Me.Tb_Cal_PowerFactor.Maximum = New Decimal(New Integer() {1, 0, 0, 0})
+        Me.Tb_Cal_PowerFactor.Value = New Decimal(New Integer() {950, 0, 0, 131072})
+
+        Me.Tb_Cal_ApparentPowerNom.DecimalPlaces = 0
+        Me.Tb_Cal_ApparentPowerNom.Minimum = New Decimal(New Integer() {0, 0, 0, 0})
+        Me.Tb_Cal_ApparentPowerNom.Maximum = New Decimal(New Integer() {100000, 0, 0, 0})
+        Me.Tb_Cal_ApparentPowerNom.Value = New Decimal(New Integer() {2400, 0, 0, 0})
         Me.Tb_Pwd_Nut = New System.Windows.Forms.TextBox()
         Me.Tb_Login_Nut = New System.Windows.Forms.TextBox()
         Me.Label3 = New System.Windows.Forms.Label()
@@ -44,6 +54,10 @@ Partial Class Pref_Gui
         Me.Tab_Calibrage = New System.Windows.Forms.TabPage()
         Me.Cbx_Freq_Input = New System.Windows.Forms.ComboBox()
         Me.Tb_BattV_Max = New System.Windows.Forms.TextBox()
+        Me.Tb_Cal_PowerFactor = New System.Windows.Forms.NumericUpDown()
+        Me.Tb_Cal_ApparentPowerNom = New System.Windows.Forms.NumericUpDown()
+        Me.Lbl_PowerFactor = New System.Windows.Forms.Label()
+        Me.Lbl_ApparentPowerNom = New System.Windows.Forms.Label()
         Me.Tb_OutV_Max = New System.Windows.Forms.TextBox()
         Me.Tb_InF_Max = New System.Windows.Forms.TextBox()
         Me.Tb_BattV_Min = New System.Windows.Forms.TextBox()
@@ -236,6 +250,10 @@ Partial Class Pref_Gui
         Me.Tab_Calibrage.Controls.Add(Me.Tb_InV_Min)
         Me.Tab_Calibrage.Controls.Add(Me.Lbl_Maxi)
         Me.Tab_Calibrage.Controls.Add(Me.Lbl_Mini)
+        Me.Tab_Calibrage.Controls.Add(Me.Lbl_PowerFactor)
+        Me.Tab_Calibrage.Controls.Add(Me.Tb_Cal_PowerFactor)
+        Me.Tab_Calibrage.Controls.Add(Me.Lbl_ApparentPowerNom)
+        Me.Tab_Calibrage.Controls.Add(Me.Tb_Cal_ApparentPowerNom)
         Me.Tab_Calibrage.Controls.Add(Me.Lbl_BattV)
         Me.Tab_Calibrage.Controls.Add(Me.Lbl_LoadUPS)
         Me.Tab_Calibrage.Controls.Add(Me.Lbl_OutputV)
diff --git a/WinNUT_V2/WinNUT-Client/Pref_Gui.vb b/WinNUT_V2/WinNUT-Client/Pref_Gui.vb
index 965abe2..e29aa81 100644
--- a/WinNUT_V2/WinNUT-Client/Pref_Gui.vb
+++ b/WinNUT_V2/WinNUT-Client/Pref_Gui.vb
@@ -25,6 +25,8 @@ Public Class Pref_Gui
         Try
             LogFile.LogTracing("Save Parameters.", LogLvl.LOG_DEBUG, Me)
             My.Settings.NUT_ServerAddress = Tb_Server_IP.Text
+            My.Settings.CAL_PowerFactor = CDbl(Tb_Cal_PowerFactor.Value)
+            My.Settings.CAL_ApparentPowerNom = CInt(Tb_Cal_ApparentPowerNom.Value)
             My.Settings.NUT_ServerPort = CInt(Tb_Port.Text)
             My.Settings.NUT_UPSName = Tb_UPS_Name.Text
             My.Settings.NUT_PollIntervalMsec = CInt(pollingIntervalValue.Value * 1000D)
@@ -303,6 +305,14 @@ Public Class Pref_Gui
     Private Sub Pref_Gui_Load(sender As Object, e As EventArgs) Handles MyBase.Load
         Icon = WinNUT.Icon
         LogFile.LogTracing("Load Pref Gui", LogLvl.LOG_DEBUG, Me)
+        Try
+            Tb_Cal_PowerFactor.Value = CDbl(My.Settings.CAL_PowerFactor)
+        Catch
+        End Try
+        Try
+            Tb_Cal_ApparentPowerNom.Value = CInt(My.Settings.CAL_ApparentPowerNom)
+        Catch
+        End Try
     End Sub
 
     ''' <summary>
diff --git a/WinNUT_V2/WinNUT-Client/WinNUT-client.vbproj b/WinNUT_V2/WinNUT-Client/WinNUT-client.vbproj
index 4ba31a3..6c27b26 100644
--- a/WinNUT_V2/WinNUT-Client/WinNUT-client.vbproj
+++ b/WinNUT_V2/WinNUT-Client/WinNUT-client.vbproj
@@ -124,6 +124,8 @@
     <TargetZone>LocalIntranet</TargetZone>
   </PropertyGroup>
   <ItemGroup>
+    <PackageReference Include="Microsoft.NETFramework.ReferenceAssemblies" Version="1.0.3" />
+
     <Reference Include="System" />
     <Reference Include="System.Configuration" />
     <Reference Include="System.Deployment" />
diff --git a/WinNUT_V2/WinNUT-Client/WinNUT.vb b/WinNUT_V2/WinNUT-Client/WinNUT.vb
index d35e48f..72aae9b 100644
--- a/WinNUT_V2/WinNUT-Client/WinNUT.vb
+++ b/WinNUT_V2/WinNUT-Client/WinNUT.vb
@@ -369,6 +369,13 @@ Public Class WinNUT
                                        My.Settings.NUT_UPSName,
                                        My.Settings.NUT_AutoReconnect)
 
+        ' Apply user-tunable watt-calculation knobs from My.Settings before
+        ' instantiating the device. These are shared via UPS_Device.RuntimeConfig
+        ' because UPS_Device lives in the Common assembly where My.Settings is
+        ' not available.
+        UPS_Device.RuntimeConfig.PowerFactor = My.Settings.CAL_PowerFactor
+        UPS_Device.RuntimeConfig.ApparentPowerNomVA = My.Settings.CAL_ApparentPowerNom
+
         UPS_Device = New UPS_Device(Nut_Config, LogFile, My.Settings.NUT_PollIntervalMsec, My.Settings.CAL_FreqInNom)
         AddHandler UPS_Device.EncounteredNUTException, AddressOf HandleNUTException
         UPS_Device.Connect_UPS(retryOnConnFailure)
diff --git a/WinNUT_V2/WinNUT-Client_Common/UPS_Device.vb b/WinNUT_V2/WinNUT-Client_Common/UPS_Device.vb
index 506f019..623fe74 100644
--- a/WinNUT_V2/WinNUT-Client_Common/UPS_Device.vb
+++ b/WinNUT_V2/WinNUT-Client_Common/UPS_Device.vb
@@ -8,7 +8,25 @@ Imports System.Windows.Forms
 Public Class UPS_Device
 #Region "Statics/Defaults"
     Private ReadOnly INVARIANT_CULTURE = CultureInfo.InvariantCulture
-    Private Const POWER_FACTOR = 0.8
+    Private Const POWER_FACTOR_DEFAULT = 0.95
+    Private Const APPARENT_POWER_DEFAULT = 2400
+
+    ' Shared configuration holder. The Client project sets this once
+    ' before instantiating UPS_Device, so the Common assembly does not
+    ' need to reference My.Settings (which is scoped to the Client
+    ' project only).
+    Public NotInheritable Class RuntimeConfig
+        Public Shared PowerFactor As Double = POWER_FACTOR_DEFAULT
+        Public Shared ApparentPowerNomVA As Integer = APPARENT_POWER_DEFAULT
+    End Class
+
+    Private ReadOnly Property POWER_FACTOR As Double
+        Get
+            Dim pf = RuntimeConfig.PowerFactor
+            If pf <= 0.0 OrElse pf > 1.0 Then Return POWER_FACTOR_DEFAULT
+            Return pf
+        End Get
+    End Property
 
     ' How many milliseconds to wait before the Reconnect routine tries again.
     Private Const DEFAULT_RECONNECT_WAIT_MS As Double = 5000
@@ -353,8 +371,13 @@ Public Class UPS_Device
                                     parsedValue = Single.Parse(GetUPSVar("output.realpower"), INVARIANT_CULTURE)
 
                                 Case PowerMethod.RPNomLoadPct
-                                    parsedValue = Double.Parse(GetUPSVar("ups.realpower.nominal"), INVARIANT_CULTURE)
-                                    parsedValue *= UPS_Datas.UPS_Value.Load / 100.0
+                                    Dim rpNom As Double
+                                    Try
+                                        rpNom = Double.Parse(GetUPSVar("ups.realpower.nominal"), INVARIANT_CULTURE)
+                                    Catch
+                                        rpNom = Config.ApparentPowerNomVA
+                                    End Try
+                                    parsedValue = rpNom * UPS_Datas.UPS_Value.Load / 100.0
 
                                 Case PowerMethod.InputNomVALoadPct
                                     Dim nomCurrent = Double.Parse(GetUPSVar("input.current.nominal"), INVARIANT_CULTURE)
diff --git a/WinNUT_V2/WinNUT-Client_Common/WinNUT-Client_Common.vbproj b/WinNUT_V2/WinNUT-Client_Common/WinNUT-Client_Common.vbproj
index 8e31f9d..3c382db 100644
--- a/WinNUT_V2/WinNUT-Client_Common/WinNUT-Client_Common.vbproj
+++ b/WinNUT_V2/WinNUT-Client_Common/WinNUT-Client_Common.vbproj
@@ -61,6 +61,8 @@
     <Optimize>true</Optimize>
   </PropertyGroup>
   <ItemGroup>
+    <PackageReference Include="Microsoft.NETFramework.ReferenceAssemblies" Version="1.0.3" />
+
     <Reference Include="System.Net.Http" />
     <Reference Include="System.Security" />
     <Reference Include="System.Windows.Forms" />