Fixes & @Intigracy's suggestion

code/modules/power/monitor.dm

@@ -24,13 +24,18 @@
 	var/tmp/next_process = 0
 
 	//Lists used for the charts.
-	var/list/demand_hist[POWER_MONITOR_HIST_SIZE]
+	var/list/demand_hist[0]
-	var/list/supply_hist[POWER_MONITOR_HIST_SIZE]
+	var/list/supply_hist[0]
-	var/list/load_hist[POWER_MONITOR_HIST_SIZE]
+	var/list/load_hist[0]
 
 /obj/machinery/power/monitor/New()
 	..()
 
+	for(var/i = 1 to POWER_MONITOR_HIST_SIZE) //The chart doesn't like lists with null.
+		demand_hist.Add(list(0))
+		supply_hist.Add(list(0))
+		load_hist.Add(list(0))
+
 	var/head = {"
 		<style type="text/css">
 			span.area
@@ -65,7 +70,7 @@
 			<canvas id="powerChart" style="width: 261px;"><!--261px is as much as possible.-->
 
 			</canvas>
-			<div id="legend"float: right;"></div>
+			<div id="legend" style="float: right;"></div>
 			<table class="table" width="100%; table-layout: fixed;">
 				<colgroup><col style="width: 180px;"/><col/></colgroup>
 				<tr><td><strong>Total power:</strong></td><td id="totPower">X W</td></tr>
@@ -111,9 +116,10 @@
 	var/delay = 0
 	delay += send_asset(user.client, "Chart.js")
 	delay += send_asset(user.client, "powerChart.js")
-	interface.show(user)
 
 	spawn(delay) //To prevent Jscript issues with resource sending.
+		interface.show(user)
+
 		interface.executeJavaScript("makeChart()", user) //Making the chart in something like $("document").ready() won't work so I do it here
 
 		for(var/i = 1 to POWER_MONITOR_HIST_SIZE)

code/modules/power/powerChart.js

@@ -9,13 +9,6 @@ function makeChart()
 	var data = {
 		labels: ["", "", "", "", "", "", "", "", "", "", "", "", "", "", ""],
 		datasets: [
-			{
-				label: "power usage",
-				fillColor: "rgba(255,100,100,0.2)",
-				strokeColor: "rgba(255,100,100,1)",
-				pointColor: "rgba(255,0,0,1)",
-				data: [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]  
-			},
 			{
 				label: "power production",
 				fillColor: "rgba(100,255,100,0.2)",
@@ -29,6 +22,13 @@ function makeChart()
 				strokeColor: "rgba(100,100,255,1)",
 				pointColor: "rgba(0,0,255,1)",
 				data: [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]                 
+			},			
+			{
+				label: "power usage",
+				fillColor: "rgba(255,100,100,0.2)",
+				strokeColor: "rgba(255,100,100,1)",
+				pointColor: "rgba(255,0,0,1)",
+				data: [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]  
 			}
 		]
 	};
@@ -89,7 +89,7 @@ function pushPowerData(demand, supply, load)
 	{
 		powerChart.removeData();
 	}
-	powerChart.addData([demand, supply, load], "");
+	powerChart.addData([supply, load, demand], "");
 }
 
 var watt_suffixes = ["W", "KW", "MW", "GW", "TW", "PW", "EW", "ZW", "YW"];
@@ -100,7 +100,7 @@ function formatWatts(wattage)
 		return "0 W";
 	}
 	var i = 0;
-	while(Math.abs(Math.round(wattage / 1000)) >= 1)
+	while(Math.abs(Math.round(wattage / 1000)) >= 1 && i < watt_suffixes.length)
 	{
 		wattage /= 1000;
 		i++;