I thought I'd share some graphs showing the output of my solar collectors and the results of my recent renovations (collector installation included) on my home energy use. Here is the heat collected (measured in kwh) plotted with the maximum daytime temperature:
The above graph is kind of "noisy". Switching to a one-week moving average smooths things out and makes it easier to convey the information:
Not surprisingly, the upgrading of windows and insulation, the switch to a high efficiency boiler and the recent installation of solar thermal collectors has resulted in an overall decrease in my natural gas use. Obviously the trend line will flatten out over the next few years and not proceed down to zero as it appears in the graph below.
Unfortunately, the trend for electricity use doesn't look as good. Over the past four years we've gone from one TV to two (each with a digital set top box), from one cell phone to four and from zero Nintendo DS's to two. Despite my use of power bars to _really_ turn things off, my electricity use has continued to creep up. (The really big spike in late 2008 was when we were getting our basement renovated and had our contractors rechargable batteries and air compressor constantly plugged in.)
Digging a little deeper into the Natual gas use, I can reformat the data to show how 2010 compared to the previous few years:
I got my solar colelctors hooked up in August and the gas use in the first few months looked fantastically low. Then in November, things didn't look so great. What happened? It turns out that November 2010 was colder than the average over the past few years:
If I take heating degree days into account so that I'm truly making and apples-to-apples comparison, I can see that I've make a significant decrease in my gas consumption.
Finally, you'll notice that the apparent spike in gas use over the summer. The reason for this is that we still burn gas for domestic hot water but in June and July there are very few heating degree days. It will be interesting to see what happens to this graph next summer now that my solar collectors are working. Think I'll be able to get a month where I hit zero?