I wasn’t satisfied with my earlier analysis of the relationship between electric usage and temperature. There was too much variability in the data to draw firm conclusions.
Recently, in MATLAB, I came across a feature, Double Y Axis, that helps clarify the relationship, making it visible in a plot.
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Figure 1. Monthly Temp in our neighborhood
Figure 2. Our electric Usage over time
Figure 3. Temps (blue) given on the left vertical. Electric (red) on the right
Temperature Plot
The seasonality of temperature is shown clearly in Figure 1. I restricted the data to the past 5 years.
When I ran it on the full range (since 1992), the ups and downs of the seasons were so close together, it masked the seasonal effect (Figure 1A).
Electric Usage Plot
The seasonality of electric usage is shown in Figure 2. Our house is all electric. People who have the luxury of different heating choices won’t have such a sharp electric distinction over the seasons.
Unfortunately, it’s hard to see in separate graphs what, if any, is the relationship of the seasonal cycles.
Double Y Axis
MATLAB has the capability to plot both temperature and usage on the same plot (Figure 3), the left Y axis marks the temperature (blue) while the right Y axis displays the usage.
Figure 3. Temps (blue) given on the left vertical. Electric usage (red) given on the right vertical
It takes some getting used to, but considering one color at a time helps. When the blue curve is high, the temperature is high. It’s summer. When the red curve is high, electricity consumption is high, but the highs are not in sync.
For instance, when the temperature (blue) is high, the electric use (red) is low. Contrariwise, when the temperature (blue) is low, the electric use (red) is high. Temperature and electric usage have opposite seasonal trends, especially in my house which uses electricity for both heating and cooling.
It still surprises me that we use so much more electricity to warm us in the winter than we use to cool ourselves in the summer.
I do recall that the attic fan helps with removing excess summer heat and the triple pane windows with some internal trickery reduced incoming summer heat rather than retarded outgoing winter warmth.
