diff --git a/doc/OpenSTA.odt b/doc/OpenSTA.odt
index b6a82082..add3f7f8 100644
Binary files a/doc/OpenSTA.odt and b/doc/OpenSTA.odt differ
diff --git a/doc/OpenSTA.pdf b/doc/OpenSTA.pdf
index 0777bd39..ada7e0f1 100644
Binary files a/doc/OpenSTA.pdf and b/doc/OpenSTA.pdf differ
diff --git a/power/Power.cc b/power/Power.cc
index a3ee7888..6ebe3576 100644
--- a/power/Power.cc
+++ b/power/Power.cc
@@ -236,6 +236,11 @@ PowerResult
 Power::power(const Instance *inst,
 	     const Corner *corner)
 {
+  if (network_->isHierarchical(inst)) {
+    PowerResult result;
+    powerInside(inst, corner, result);
+    return result;
+  }
   LibertyCell *cell = network_->libertyCell(inst);
   if (cell) {
     ensureActivities();
@@ -244,6 +249,27 @@ Power::power(const Instance *inst,
   return PowerResult();
 }
 
+void
+Power::powerInside(const Instance *hinst,
+                   const Corner *corner,
+                   PowerResult &result)
+{
+  InstanceChildIterator *child_iter = network_->childIterator(hinst);
+  while (child_iter->hasNext()) {
+    Instance *child = child_iter->next();
+    if (network_->isHierarchical(child))
+      powerInside(child, corner, result);
+    else {
+      LibertyCell *cell = network_->libertyCell(child);
+      if (cell) {
+        PowerResult inst_power = power(child, cell, corner);
+        result.incr(inst_power);
+      }
+    }
+  }
+  delete child_iter;
+}
+
 ////////////////////////////////////////////////////////////////
 
 class ActivitySrchPred : public SearchPredNonLatch2
diff --git a/power/Power.hh b/power/Power.hh
index 73a6110b..293bb3c5 100644
--- a/power/Power.hh
+++ b/power/Power.hh
@@ -87,6 +87,9 @@ public:
   PwrActivity findClkedActivity(const Pin *pin);
 
 protected:
+  void powerInside(const Instance *hinst,
+                   const Corner *corner,
+                   PowerResult &result);
   void ensureActivities();
   bool hasUserActivity(const Pin *pin);
   PwrActivity &userActivity(const Pin *pin);