diff --git a/opt/inverter/pvoutput.php b/opt/inverter/pvoutput.php
index 13b89d4..a9e43cf 100644
--- a/opt/inverter/pvoutput.php
+++ b/opt/inverter/pvoutput.php
@@ -1,9 +1,9 @@
 #!/usr/bin/php
 <?php
 require_once 'functions.php';
+require_once 'rrd.php';
 
 define('RRD_FILE', 'data/inverter_%s_today.rrd');
-define('RRD_FETCH', 'rrdtool fetch %s AVERAGE -r %d -s %d -e %d');
 define('PVOUTPUT_URL', 'http://pvoutput.org/service/r1/addstatus.jsp');
 define('TODAY_FILE', 'data/today_%s.csv');
 define('FIELD', 'PAC');
@@ -48,11 +48,7 @@ $iLast = $aToday[2];
 
 /* Extract fields */
 $iTime = time();
-$sData = command(sprintf(RRD_FETCH, sprintf(RRD_FILE, $sSerial), RESOLUTION, $iLast, $iTime));
-$aData = explode("\n", trim($sData));
-$aFields = preg_split("~[\s]+~", array_shift($aData));
-array_shift($aData);
-$aFields = array_flip($aFields);
+list($aFields, $aData) = RRD::fetch(sprintf(RRD_FILE, $sSerial), RESOLUTION, $iLast, $iTime, 'AVERAGE');
 
 /* Process data */
 $bFirst = true;
@@ -60,8 +56,7 @@ $fEnergy = 0;
 if (isset($aFields[FIELD])) {
     $iField = $aFields[FIELD] + 1;
     array_shift($aData);
-    foreach ($aData as $sRow) {
-        $aRow = explode(' ', $sRow);
+    foreach ($aData as $aRow) {
         $iDate = substr($aRow[0], 0, -1);
         $iInterval = $bFirst ? (($bFirst = false) || RESOLUTION) : $iDate - $iLast; // s
         if (($fValue = floatval($aRow[$iField])) > 0) { // W
diff --git a/opt/inverter/rrd.php b/opt/inverter/rrd.php
index ce175fc..bfbf411 100644
--- a/opt/inverter/rrd.php
+++ b/opt/inverter/rrd.php
@@ -9,7 +9,7 @@ class RRD {
     protected static $aPipes = array();
 
     protected function __construct() {
-        self::$rProcess= proc_open('rrdtool -', array(
+        self::$rProcess = proc_open('rrdtool -', array(
            0 => array('pipe', 'r'),
            1 => array('pipe', 'w')), self::$aPipes);
         stream_set_blocking(self::$aPipes[1], false);
@@ -19,7 +19,7 @@ class RRD {
         if (!isset(self::$rProcess)) {
             self::$oInstance = new self();
         }
-        var_dump($sCommand);
+        //echo $sCommand . "\n";
         fwrite(self::$aPipes[0], $sCommand . PHP_EOL);
         $nNull = null;
         $aRead = array(self::$aPipes[1]);
@@ -45,14 +45,17 @@ class RRD {
         $aFields = array_flip($aFields);
         array_shift($aData);
         array_pop($aData);
-        foreach ($aData as $iKey => $sRow) {
+        $aValues = array();
+        foreach ($aData as $sRow) {
             $aRow = explode(':', $sRow);
             $iTime = current($aRow);
-            $mValue = trim(next($aRow));
-            if ($mValue != '-nan') {
-                $aValues[$iTime] = floatval($mValue);
+            $aRow = explode(' ', trim(next($aRow)));
+            foreach ($aRow as $iKey => $mValue) {
+                if (strpos($mValue, 'nan') !== false) {
+                    $aRow[$iKey] = null;
+                }                
             }
-            //$aValues[$iTime] = $fValue == 0 ? null : $fValue;
+            $aValues[$iTime] = $aRow;
         }
         return array($aFields, $aValues);
     }