energy hook plots

The graph above shows monthly averaged temperature on the horizontal access and the BTUs per square foot on the vertical access for our house. I'm calling this a "hook plot" because, well, it looks like a hook! The BTUs include energy from gas and electricity. The graph is hooked because we have, interestingly enough, more energy consumption during the cooler, winter months than the warmer, summer months. The low at about 60 to 70 degrees are the shoulder seasons--spring and fall when we don't heat or cool the house.

The above plot includes only the months since we installed and activated the photovoltaics. Without the PV, the warmer side of the graph rises about 500 BTUs per square foot.

Now here's the hook plot for our old house, the 1880s shotgun in central Austin:

Yikes! The maximum BTUs per square foot of our new house are in the bottom range of the old house. That tells you what single pane glass and uninsulated walls get you. To be fair, the new house is about twice as large as the old house, but even there, the new house is kicking the old house's butt.

Anyway, I made these plots wondering if there was a solid relationship between temperature and energy consumption, which, of course, there is.