diff --git a/system/options.nix b/system/options.nix
index 6b0f725ab2f..6e165c3b00a 100644
--- a/system/options.nix
+++ b/system/options.nix
@@ -2186,7 +2186,20 @@ in
     };
 
   };
+
+    
+  powerManagement = {
+    
+    enable = mkOption {
+      default = false;
+      description = "
+        Whether to enable power management.
+      ";
+    };
+
+  };
   
+
   nesting = {
     children = mkOption {
       default = [];
@@ -2196,6 +2209,7 @@ in
     };
   };
 
+  
   passthru = mkOption {
     default = {};
     description = "
diff --git a/upstart-jobs/acpid.nix b/upstart-jobs/acpid.nix
index efd608e1353..3a7df58bbaf 100644
--- a/upstart-jobs/acpid.nix
+++ b/upstart-jobs/acpid.nix
@@ -15,6 +15,9 @@ let
 
       event=button/lid.*
       action=${lidEventHandler} "%e"
+
+      event=ac_adapter.*
+      action=${acEventHandler} "%e"
     '';
 
   # Called when the power button is pressed.
@@ -23,7 +26,6 @@ let
       #! ${pkgs.bash}/bin/sh
       # Suspend to RAM.
       #echo mem > /sys/power/state
-      exit 0
     '';
 
   # Called when the laptop lid is opened/closed.
@@ -38,8 +40,18 @@ let
           sync
           echo mem > /sys/power/state
       fi
+    '';
 
-      exit 0
+  # Called when the AC power is connected or disconnected.
+  acEventHandler = pkgs.writeScript "ac-power.sh"
+    ''
+      #! ${pkgs.bash}/bin/sh
+
+      if grep -q "state:.*on-line" /proc/acpi/ac_adapter/AC/state; then
+         echo performance > /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor
+      elif grep -q "state:.*off-line" /proc/acpi/ac_adapter/AC/state; then
+         echo ondemand > /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor
+      fi
     '';
 
 in
diff --git a/upstart-jobs/default.nix b/upstart-jobs/default.nix
index 9fb19188581..ea5d8fcdbe0 100644
--- a/upstart-jobs/default.nix
+++ b/upstart-jobs/default.nix
@@ -361,7 +361,7 @@ let
     })
 
   # ACPI daemon.
-  ++ optional true /* !!! need some option */
+  ++ optional config.powerManagement.enable
     (import ../upstart-jobs/acpid.nix {
       inherit config pkgs;
     })