diff --git a/opt/inverter/create_rrd.php b/opt/inverter/create_rrd.php
new file mode 100644
index 0000000..37cc748
--- /dev/null
+++ b/opt/inverter/create_rrd.php
@@ -0,0 +1,74 @@
+#!/usr/local/bin/php
+<?php
+$aRRDFile = 'today.rrd';
+$sDataDirectory = 'data';
+$aRRDCreate = array(
+    'inverter.rrd' => 'create %s
+    --step 5
+    --start %d
+    DS:TEMP:GAUGE:120:U:U
+    DS:VPV:GAUGE:120:U:U
+    DS:IAC:GAUGE:120:U:U
+    DS:VAC:GAUGE:120:U:U
+    DS:FAC:GAUGE:120:U:U
+    DS:PAC:GAUGE:120:0:U
+    DS:ETOTAL:GAUGE:120:0:U
+    DS:ETODAY:GAUGE:120:0:U
+    RRA:AVERAGE:0.5:1:720
+    RRA:AVERAGE:0.5:17:1017
+    RRA:AVERAGE:0.5:120:1008
+    RRA:AVERAGE:0.5:535:1002
+    RRA:AVERAGE:0.5:6324:1001',
+    'today.rrd' => 'create %s
+    --step 5
+    --start %d    
+    DS:PAC:GAUGE:120:0:U
+    DS:ETODAY:GAUGE:120:0:U
+    RRA:AVERAGE:0.5:1:17280');
+$aRRDFiles = array_keys($aRRDCreate);
+
+/* Spawn process that accepts commands from STDIN */
+$rHandle = popen('rrdtool - > /dev/null', 'w');
+$bFirst = true;
+$aRRDKeys = array();
+$i = 0;
+foreach (glob($sDataDirectory . '/*.csv') as $sFile) {
+    /* Extract header from csv file */
+    $aData = explode("\n", trim(file_get_contents($sFile)));
+    $sHeader = array_shift($aData);
+    
+    if ($bFirst) {
+        $aHeader = array_flip(explode(',', $sHeader));
+        foreach ($aRRDCreate as $sRRDFile => $sRRDCreate) {
+            /* Determine fields to update in RRD database */
+            preg_match_all('~DS:([^:]+):~', $sRRDCreate, $aMatches);
+            $aKeys = array();
+            foreach ($aMatches[1] as $sField) {
+                $aKeys[] = $aHeader[$sField] - 1;
+            }
+            $aRRDKeys[$sRRDFile] = array_flip($aKeys);            
+        }
+    }
+
+    foreach ($aData as $sEntry) {
+        $aValues = array_slice(explode(',', $sEntry), 1, 12);
+        if ($bFirst) {
+            foreach ($aRRDCreate as $sRRDFile => $sRRDCreate) {
+                /* Create RRD database */
+                echo $sCommand = str_replace("\n", ' ', sprintf($sRRDCreate, $sRRDFile, $aValues[0] - 1)) . "\n";
+                fwrite($rHandle, $sCommand);
+            }
+            $bFirst = false;
+        }
+        ++$i;
+        foreach ($aRRDFiles as $sRRDFile) {
+            /* Update relevant fields in RRD database */
+            $aRRDValues = array_intersect_key($aValues, $aRRDKeys[$sRRDFile]);
+            $sCommand = sprintf("update %s %d:%s\n", $sRRDFile, $aValues[0], implode(':', $aRRDValues));
+            printf('[%d] %s', $i, $sCommand); 
+            fwrite($rHandle, $sCommand);
+        }
+    }
+}
+fwrite($rHandle, "quit\n");
+pclose($rHandle);
\ No newline at end of file
diff --git a/opt/inverter/fetch_rrd.php b/opt/inverter/fetch_rrd.php
new file mode 100644
index 0000000..47e27ce
--- /dev/null
+++ b/opt/inverter/fetch_rrd.php
@@ -0,0 +1,46 @@
+#!/usr/local/bin/php
+<?php
+echo '<pre>';
+$sRRDFile = 'inverter.rrd';
+$sRRDFetch = 'rrdtool fetch %s AVERAGE -r %d -s %d -e %d';
+$sField = 'PAC';
+
+/* Constrain data to fetch */
+$iLast = strtotime('9:00');
+$iStart = $iLast;
+$iEnd = strtotime('17:00');
+$iResolution = 5;
+
+/* Extract fields */
+$sData = command(sprintf($sRRDFetch, $sRRDFile, $iResolution, $iStart, $iEnd));
+$aData = explode("\n", trim($sData));
+$aFields = preg_split("~[\s]+~", array_shift($aData));
+array_shift($aData);
+$aFields = array_flip($aFields);
+
+$bFirst = true;
+$fTotal = 0;
+if (isset($aFields[$sField])) {
+    $iField = $aFields[$sField] + 1;
+    array_shift($aData);
+    foreach ($aData as $sRow) {
+        $aRow = explode(' ', $sRow);
+        if ($bFirst) var_dump($aRow);
+        $iDate = substr($aRow[0], 0, -1);
+        $iInterval = $bFirst ? (($bFirst = false) || $iResolution) : $iDate - $iLast;
+        if (($fValue = floatval($aRow[$iField])) > 0) {        
+            $fTotal += $iInterval * $fValue;
+        }
+        $iLast = $iDate;
+    }    
+}
+
+/* Convert to kWh */
+var_dump(count($aData));
+var_dump($fTotal / 1000 / 3600);
+
+function command($sCommand) {
+    ob_start();
+    system($sCommand);
+    return ob_get_clean();
+}
\ No newline at end of file