diff --git a/Classes/PHPExcel/CachedObjectStorage/APC.php b/Classes/PHPExcel/CachedObjectStorage/APC.php
index f8e64587..f6d974fe 100644
--- a/Classes/PHPExcel/CachedObjectStorage/APC.php
+++ b/Classes/PHPExcel/CachedObjectStorage/APC.php
@@ -41,11 +41,14 @@ class PHPExcel_CachedObjectStorage_APC extends PHPExcel_CachedObjectStorage_Cach
 
 
 	private function _storeData() {
-		$this->_currentObject->detach();
+		if ($this->_currentCellIsDirty) {
+			$this->_currentObject->detach();
 
-		if (!apc_store($this->_cachePrefix.$this->_currentObjectID.'.cache',serialize($this->_currentObject),$this->_cacheTime)) {
-			$this->__destruct();
-			throw new Exception('Failed to store cell '.$cellID.' in APC');
+			if (!apc_store($this->_cachePrefix.$this->_currentObjectID.'.cache',serialize($this->_currentObject),$this->_cacheTime)) {
+				$this->__destruct();
+				throw new Exception('Failed to store cell '.$cellID.' in APC');
+			}
+			$this->_currentCellIsDirty = false;
 		}
 		$this->_currentObjectID = $this->_currentObject = null;
 	}	//	function _storeData()
@@ -67,6 +70,7 @@ class PHPExcel_CachedObjectStorage_APC extends PHPExcel_CachedObjectStorage_Cach
 
 		$this->_currentObjectID = $pCoord;
 		$this->_currentObject = $cell;
+		$this->_currentCellIsDirty = true;
 
 		return $cell;
 	}	//	function addCacheData()
diff --git a/Classes/PHPExcel/CachedObjectStorage/CacheBase.php b/Classes/PHPExcel/CachedObjectStorage/CacheBase.php
index e3d14b5f..6119a348 100644
--- a/Classes/PHPExcel/CachedObjectStorage/CacheBase.php
+++ b/Classes/PHPExcel/CachedObjectStorage/CacheBase.php
@@ -57,6 +57,13 @@ class PHPExcel_CachedObjectStorage_CacheBase {
 	protected $_currentObjectID = null;
 
 
+	/**
+	 *	Flag indicating whether the currently active Cell requires saving
+	 *
+	 *	@var boolean
+	 */
+	protected $_currentCellIsDirty = true;
+
 	/**
 	 *	An array of cells or cell pointers for the worksheet cells held in this cache,
 	 *		and indexed by their coordinate address within the worksheet
@@ -118,6 +125,7 @@ class PHPExcel_CachedObjectStorage_CacheBase {
 			$this->_cellCache[$pCoord]->detach();
 			unset($this->_cellCache[$pCoord]);
 		}
+		$this->_currentCellIsDirty = false;
 	}	//	function deleteCacheData()
 
 
diff --git a/Classes/PHPExcel/CachedObjectStorage/DiscISAM.php b/Classes/PHPExcel/CachedObjectStorage/DiscISAM.php
index 327f4b4e..84ffcc95 100644
--- a/Classes/PHPExcel/CachedObjectStorage/DiscISAM.php
+++ b/Classes/PHPExcel/CachedObjectStorage/DiscISAM.php
@@ -40,14 +40,17 @@ class PHPExcel_CachedObjectStorage_DiscISAM extends PHPExcel_CachedObjectStorage
 
 
 	private function _storeData() {
-		$this->_currentObject->detach();
+		if ($this->_currentCellIsDirty) {
+			$this->_currentObject->detach();
 
-		fseek($this->_fileHandle,0,SEEK_END);
-		$offset = ftell($this->_fileHandle);
-		fwrite($this->_fileHandle, serialize($this->_currentObject));
-		$this->_cellCache[$this->_currentObjectID]	= array('ptr' => $offset,
-															'sz'  => ftell($this->_fileHandle) - $offset
-														   );
+			fseek($this->_fileHandle,0,SEEK_END);
+			$offset = ftell($this->_fileHandle);
+			fwrite($this->_fileHandle, serialize($this->_currentObject));
+			$this->_cellCache[$this->_currentObjectID]	= array('ptr' => $offset,
+																'sz'  => ftell($this->_fileHandle) - $offset
+															   );
+			$this->_currentCellIsDirty = false;
+		}
 		$this->_currentObjectID = $this->_currentObject = null;
 	}	//	function _storeData()
 
@@ -67,6 +70,7 @@ class PHPExcel_CachedObjectStorage_DiscISAM extends PHPExcel_CachedObjectStorage
 
 		$this->_currentObjectID = $pCoord;
 		$this->_currentObject = $cell;
+		$this->_currentCellIsDirty = true;
 
 		return $cell;
 	}	//	function addCacheData()
diff --git a/Classes/PHPExcel/CachedObjectStorage/Memcache.php b/Classes/PHPExcel/CachedObjectStorage/Memcache.php
index e40413ed..28b74e39 100644
--- a/Classes/PHPExcel/CachedObjectStorage/Memcache.php
+++ b/Classes/PHPExcel/CachedObjectStorage/Memcache.php
@@ -43,14 +43,17 @@ class PHPExcel_CachedObjectStorage_Memcache extends PHPExcel_CachedObjectStorage
 
 
 	private function _storeData() {
-		$this->_currentObject->detach();
+		if ($this->_currentCellIsDirty) {
+			$this->_currentObject->detach();
 
-		$obj = serialize($this->_currentObject);
-		if (!$this->_memcache->replace($this->_cachePrefix.$this->_currentObjectID.'.cache',$obj,NULL,$this->_cacheTime)) {
-			if (!$this->_memcache->add($this->_cachePrefix.$this->_currentObjectID.'.cache',$obj,NULL,$this->_cacheTime)) {
-				$this->__destruct();
-				throw new Exception('Failed to store cell '.$cellID.' in MemCache');
+			$obj = serialize($this->_currentObject);
+			if (!$this->_memcache->replace($this->_cachePrefix.$this->_currentObjectID.'.cache',$obj,NULL,$this->_cacheTime)) {
+				if (!$this->_memcache->add($this->_cachePrefix.$this->_currentObjectID.'.cache',$obj,NULL,$this->_cacheTime)) {
+					$this->__destruct();
+					throw new Exception('Failed to store cell '.$cellID.' in MemCache');
+				}
 			}
+			$this->_currentCellIsDirty = false;
 		}
 		$this->_currentObjectID = $this->_currentObject = null;
 	}	//	function _storeData()
@@ -72,6 +75,7 @@ class PHPExcel_CachedObjectStorage_Memcache extends PHPExcel_CachedObjectStorage
 
 		$this->_currentObjectID = $pCoord;
 		$this->_currentObject = $cell;
+		$this->_currentCellIsDirty = true;
 
 		return $cell;
 	}	//	function addCacheData()
diff --git a/Classes/PHPExcel/CachedObjectStorage/MemoryGZip.php b/Classes/PHPExcel/CachedObjectStorage/MemoryGZip.php
index dfe359ef..4fb90adb 100644
--- a/Classes/PHPExcel/CachedObjectStorage/MemoryGZip.php
+++ b/Classes/PHPExcel/CachedObjectStorage/MemoryGZip.php
@@ -36,9 +36,12 @@
 class PHPExcel_CachedObjectStorage_MemoryGZip extends PHPExcel_CachedObjectStorage_CacheBase implements PHPExcel_CachedObjectStorage_ICache {
 
 	private function _storeData() {
-		$this->_currentObject->detach();
+		if ($this->_currentCellIsDirty) {
+			$this->_currentObject->detach();
 
-		$this->_cellCache[$this->_currentObjectID] = gzdeflate(serialize($this->_currentObject));
+			$this->_cellCache[$this->_currentObjectID] = gzdeflate(serialize($this->_currentObject));
+			$this->_currentCellIsDirty = false;
+		}
 		$this->_currentObjectID = $this->_currentObject = null;
 	}	//	function _storeData()
 
@@ -58,6 +61,7 @@ class PHPExcel_CachedObjectStorage_MemoryGZip extends PHPExcel_CachedObjectStora
 
 		$this->_currentObjectID = $pCoord;
 		$this->_currentObject = $cell;
+		$this->_currentCellIsDirty = true;
 
 		return $cell;
 	}	//	function addCacheData()
diff --git a/Classes/PHPExcel/CachedObjectStorage/MemorySerialized.php b/Classes/PHPExcel/CachedObjectStorage/MemorySerialized.php
index ca8f0317..14abd793 100644
--- a/Classes/PHPExcel/CachedObjectStorage/MemorySerialized.php
+++ b/Classes/PHPExcel/CachedObjectStorage/MemorySerialized.php
@@ -36,9 +36,12 @@
 class PHPExcel_CachedObjectStorage_MemorySerialized extends PHPExcel_CachedObjectStorage_CacheBase implements PHPExcel_CachedObjectStorage_ICache {
 
 	private function _storeData() {
-		$this->_currentObject->detach();
+		if ($this->_currentCellIsDirty) {
+			$this->_currentObject->detach();
 
-		$this->_cellCache[$this->_currentObjectID] = serialize($this->_currentObject);
+			$this->_cellCache[$this->_currentObjectID] = serialize($this->_currentObject);
+			$this->_currentCellIsDirty = false;
+		}
 		$this->_currentObjectID = $this->_currentObject = null;
 	}	//	function _storeData()
 
@@ -58,6 +61,7 @@ class PHPExcel_CachedObjectStorage_MemorySerialized extends PHPExcel_CachedObjec
 
 		$this->_currentObjectID = $pCoord;
 		$this->_currentObject = $cell;
+		$this->_currentCellIsDirty = true;
 
 		return $cell;
 	}	//	function addCacheData()
diff --git a/Classes/PHPExcel/CachedObjectStorage/PHPTemp.php b/Classes/PHPExcel/CachedObjectStorage/PHPTemp.php
index 07caa85c..2919aa08 100644
--- a/Classes/PHPExcel/CachedObjectStorage/PHPTemp.php
+++ b/Classes/PHPExcel/CachedObjectStorage/PHPTemp.php
@@ -41,14 +41,17 @@ class PHPExcel_CachedObjectStorage_PHPTemp extends PHPExcel_CachedObjectStorage_
 	private $_memoryCacheSize = null;
 
 	private function _storeData() {
-		$this->_currentObject->detach();
+		if ($this->_currentCellIsDirty) {
+			$this->_currentObject->detach();
 
-		fseek($this->_fileHandle,0,SEEK_END);
-		$offset = ftell($this->_fileHandle);
-		fwrite($this->_fileHandle, serialize($this->_currentObject));
-		$this->_cellCache[$this->_currentObjectID]	= array('ptr' => $offset,
-															'sz'  => ftell($this->_fileHandle) - $offset
-														   );
+			fseek($this->_fileHandle,0,SEEK_END);
+			$offset = ftell($this->_fileHandle);
+			fwrite($this->_fileHandle, serialize($this->_currentObject));
+			$this->_cellCache[$this->_currentObjectID]	= array('ptr' => $offset,
+																'sz'  => ftell($this->_fileHandle) - $offset
+															   );
+			$this->_currentCellIsDirty = false;
+		}
 		$this->_currentObjectID = $this->_currentObject = null;
 	}	//	function _storeData()
 
@@ -68,6 +71,7 @@ class PHPExcel_CachedObjectStorage_PHPTemp extends PHPExcel_CachedObjectStorage_
 
 		$this->_currentObjectID = $pCoord;
 		$this->_currentObject = $cell;
+		$this->_currentCellIsDirty = true;
 
 		return $cell;
 	}	//	function addCacheData()
diff --git a/Classes/PHPExcel/CachedObjectStorage/Wincache.php b/Classes/PHPExcel/CachedObjectStorage/Wincache.php
index 6c2cfd29..14435b13 100644
--- a/Classes/PHPExcel/CachedObjectStorage/Wincache.php
+++ b/Classes/PHPExcel/CachedObjectStorage/Wincache.php
@@ -41,19 +41,22 @@ class PHPExcel_CachedObjectStorage_Wincache extends PHPExcel_CachedObjectStorage
 
 
 	private function _storeData() {
-		$this->_currentObject->detach();
+		if ($this->_currentCellIsDirty) {
+			$this->_currentObject->detach();
 
-		$obj = serialize($this->_currentObject);
-		if (wincache_ucache_exists($this->_cachePrefix.$this->_currentObjectID.'.cache')) {
-			if (!wincache_ucache_set($this->_cachePrefix.$this->_currentObjectID.'.cache', $obj, $this->_cacheTime)) {
-				$this->__destruct();
-				throw new Exception('Failed to store cell '.$cellID.' in WinCache');
-			}
-		} else {
-			if (!wincache_ucache_add($this->_cachePrefix.$this->_currentObjectID.'.cache', $obj, $this->_cacheTime)) {
-				$this->__destruct();
-				throw new Exception('Failed to store cell '.$cellID.' in WinCache');
+			$obj = serialize($this->_currentObject);
+			if (wincache_ucache_exists($this->_cachePrefix.$this->_currentObjectID.'.cache')) {
+				if (!wincache_ucache_set($this->_cachePrefix.$this->_currentObjectID.'.cache', $obj, $this->_cacheTime)) {
+					$this->__destruct();
+					throw new Exception('Failed to store cell '.$cellID.' in WinCache');
+				}
+			} else {
+				if (!wincache_ucache_add($this->_cachePrefix.$this->_currentObjectID.'.cache', $obj, $this->_cacheTime)) {
+					$this->__destruct();
+					throw new Exception('Failed to store cell '.$cellID.' in WinCache');
+				}
 			}
+			$this->_currentCellIsDirty = false;
 		}
 
 		$this->_currentObjectID = $this->_currentObject = null;
@@ -76,6 +79,7 @@ class PHPExcel_CachedObjectStorage_Wincache extends PHPExcel_CachedObjectStorage
 
 		$this->_currentObjectID = $pCoord;
 		$this->_currentObject = $cell;
+		$this->_currentCellIsDirty = true;
 
 		return $cell;
 	}	//	function addCacheData()
diff --git a/changelog.txt b/changelog.txt
index fbca91b4..ad48976f 100644
--- a/changelog.txt
+++ b/changelog.txt
@@ -25,6 +25,7 @@
 
 Fixed in SVN:
 - General:  (MBaker) Fix to build to ensure that Examples are included with the documentation
+- General:  (MBaker) Reduce cell caching overhead using dirty flag to ensure that cells are only rewritten to the cache if they have actually been changed
 - Bugfix:   (MBaker) Work item 15459 - Invalid cell coordinate in Autofilter for Excel2007 Writer
 - Bugfix:   (MBaker) Work item 15518 - PCLZip library issue
 - Bugfix:   (MBaker) Work item 15537 - Excel2007 Reader canRead function bug