diff --git a/doc/OpenSTA.odt b/doc/OpenSTA.odt
index 495ea6fb..488139bd 100644
Binary files a/doc/OpenSTA.odt and b/doc/OpenSTA.odt differ
diff --git a/doc/OpenSTA.pdf b/doc/OpenSTA.pdf
index f20e6fea..233d2857 100644
Binary files a/doc/OpenSTA.pdf and b/doc/OpenSTA.pdf differ
diff --git a/include/sta/PowerClass.hh b/include/sta/PowerClass.hh
index 5b5fbf5f..ed4a4860 100644
--- a/include/sta/PowerClass.hh
+++ b/include/sta/PowerClass.hh
@@ -49,6 +49,7 @@ public:
   PwrActivity(float density,
 	      float duty,
 	      PwrActivityOrigin origin);
+  void init();
   float density() const { return density_; }
   void setDensity(float density);
   float duty() const { return duty_; }
diff --git a/power/Power.cc b/power/Power.cc
index b66681e1..25d1cb2d 100644
--- a/power/Power.cc
+++ b/power/Power.cc
@@ -112,6 +112,13 @@ Power::setGlobalActivity(float density,
   activities_valid_ = false;
 }
   
+void
+Power::unsetGlobalActivity()
+{
+  global_activity_.init();
+  activities_valid_ = false;
+}
+
 void
 Power::setInputActivity(float density,
 			float duty)
@@ -120,6 +127,13 @@ Power::setInputActivity(float density,
   activities_valid_ = false;
 }
 
+void
+Power::unsetInputActivity()
+{
+  input_activity_.init();
+  activities_valid_ = false;
+}
+
 void
 Power::setInputPortActivity(const Port *input_port,
 			    float density,
@@ -133,6 +147,17 @@ Power::setInputPortActivity(const Port *input_port,
   }
 }
 
+void
+Power::unsetInputPortActivity(const Port *input_port)
+{
+  Instance *top_inst = network_->topInstance();
+  const Pin *pin = network_->findPin(top_inst, input_port);
+  if (pin) {
+    user_activity_map_.erase(pin);
+    activities_valid_ = false;
+  }
+}
+
 void
 Power::setUserActivity(const Pin *pin,
                        float density,
@@ -143,6 +168,13 @@ Power::setUserActivity(const Pin *pin,
   activities_valid_ = false;
 }
 
+void
+Power::unsetUserActivity(const Pin *pin)
+{
+  user_activity_map_.erase(pin);
+  activities_valid_ = false;
+}
+
 PwrActivity &
 Power::userActivity(const Pin *pin)
 {
@@ -664,7 +696,7 @@ Power::ensureActivities()
 
       // Initialize default input activity (after sdc is defined)
       // unless it has been set by command.
-      if (input_activity_.density() == 0.0) {
+      if (input_activity_.origin() == PwrActivityOrigin::unknown) {
         float min_period = clockMinPeriod();
         float density = 0.1 / (min_period != 0.0
                                ? min_period
@@ -1535,6 +1567,7 @@ PwrActivity::PwrActivity(float density,
   duty_(duty),
   origin_(origin)
 {
+  check();
 }
 
 PwrActivity::PwrActivity() :
@@ -1542,7 +1575,6 @@ PwrActivity::PwrActivity() :
   duty_(0.0),
   origin_(PwrActivityOrigin::unknown)
 {
-  check();
 }
 
 void
@@ -1563,6 +1595,14 @@ PwrActivity::setOrigin(PwrActivityOrigin origin)
   origin_ = origin;
 }
 
+void
+PwrActivity::init()
+{
+  density_ = 0.0;
+  duty_ = 0.0;
+  origin_ = PwrActivityOrigin::unknown;
+}
+
 void
 PwrActivity::set(float density,
 		 float duty,
diff --git a/power/Power.hh b/power/Power.hh
index f28a7946..f4fde251 100644
--- a/power/Power.hh
+++ b/power/Power.hh
@@ -87,16 +87,20 @@ public:
                     const Corner *corner);
   void setGlobalActivity(float activity,
 			 float duty);
+  void unsetGlobalActivity();
   void setInputActivity(float activity,
 			float duty);
+  void unsetInputActivity();
   void setInputPortActivity(const Port *input_port,
 			    float activity,
 			    float duty);
+  void unsetInputPortActivity(const Port *input_port);
   PwrActivity pinActivity(const Pin *pin);
   void setUserActivity(const Pin *pin,
 		       float activity,
 		       float duty,
 		       PwrActivityOrigin origin);
+  void unsetUserActivity(const Pin *pin);
   void reportActivityAnnotation(bool report_unannotated,
                                 bool report_annotated);
   float clockMinPeriod();
diff --git a/power/Power.i b/power/Power.i
index e2e0ed50..cdc59840 100644
--- a/power/Power.i
+++ b/power/Power.i
@@ -84,6 +84,13 @@ set_power_global_activity(float activity,
   power->setGlobalActivity(activity, duty);
 }
 
+void
+unset_power_global_activity()
+{
+  Power *power = Sta::sta()->power();
+  power->unsetGlobalActivity();
+}
+
 void
 set_power_input_activity(float activity,
 			 float duty)
@@ -92,6 +99,13 @@ set_power_input_activity(float activity,
   return power->setInputActivity(activity, duty);
 }
 
+void
+unset_power_input_activity()
+{
+  Power *power = Sta::sta()->power();
+  return power->unsetInputActivity();
+}
+
 void
 set_power_input_port_activity(const Port *input_port,
 			      float activity,
@@ -101,6 +115,13 @@ set_power_input_port_activity(const Port *input_port,
   return power->setInputPortActivity(input_port, activity, duty);
 }
 
+void
+unset_power_input_port_activity(const Port *input_port)
+{
+  Power *power = Sta::sta()->power();
+  return power->unsetInputPortActivity(input_port);
+}
+
 void
 set_power_pin_activity(const Pin *pin,
 		       float activity,
@@ -110,6 +131,13 @@ set_power_pin_activity(const Pin *pin,
   return power->setUserActivity(pin, activity, duty, PwrActivityOrigin::user);
 }
 
+void
+unset_power_pin_activity(const Pin *pin)
+{
+  Power *power = Sta::sta()->power();
+  return power->unsetUserActivity(pin);
+}
+
 float
 clock_min_period()
 {
diff --git a/power/Power.tcl b/power/Power.tcl
index feebc7c1..d38d4cbb 100644
--- a/power/Power.tcl
+++ b/power/Power.tcl
@@ -289,7 +289,7 @@ proc set_power_activity { args } {
     foreach port $ports {
       if { [get_property $port "direction"] == "input" } {
 	if { [is_clock_src [sta::get_port_pin $port]] } {
-          sta_warn 303 "activity cannot be set on clock ports."
+          sta_warn 310 "activity cannot be set on clock ports."
         } else {
           set_power_input_port_activity $port $density $duty
         }
@@ -306,6 +306,47 @@ proc set_power_activity { args } {
 
 ################################################################
 
+define_cmd_args "unset_power_activity" { [-global]\
+                                           [-input]\
+                                           [-input_ports ports]\
+                                           [-pins pins]\
+                                           [-clock clock]}
+
+proc unset_power_activity { args } {
+  parse_key_args "unset_power_activity" args \
+    keys {-input_ports -pins -clock} \
+    flags {-global -input}
+
+  check_argc_eq0 "unset_power_activity" $args
+
+  if { [info exists flags(-global)] } {
+    unset_power_global_activity
+  }
+  if { [info exists flags(-input)] } {
+    unset_power_input_activity
+  }
+  if { [info exists keys(-input_ports)] } {
+    set ports [get_ports_error "input_ports" $keys(-input_ports)]
+    foreach port $ports {
+      if { [get_property $port "direction"] == "input" } {
+	if { [is_clock_src [sta::get_port_pin $port]] } {
+          sta_warn 303 "activity cannot be set on clock ports."
+        } else {
+          unset_power_input_port_activity $port
+        }
+      }
+    }
+  }
+  if { [info exists keys(-pins)] } {
+    set pins [get_pins $keys(-pins)]
+    foreach pin $pins {
+      unset_power_pin_activity $pin
+    }
+  }
+}
+
+################################################################
+
 # Deprecated 9/2024
 define_cmd_args "read_power_activities" { [-scope scope] -vcd filename }