Wednesday, June 07, 2017

The Impact of Power Conservation in the Suburban 5-4-and-a-Door

In preparation for a solar panel installation, it is important to understand your current electricity usage so that the panels can be scaled appropriated and the expected return on investment (ROI) can be calculated. As we are getting panels installed on our home now, I requested as many back bills from the power company as they could provide. In my case that turned out to be about 4 years' worth of bills. We scaled our installation based on our recent power use, but the total data was entertaining for a numbers-oriented person to analyze.

The ROI calculations will come later, once we have the electrical hooked up and have been running it for a while. What was interesting even before hooking up the solar array is the obvious impact we found from our multi-year electrical conservation efforts. You always wonder if the little things that you're doing actually make a difference. In this case, they certainly have.

When we first moved into our home, we replaced a lot of the incandescent bulbs with compact florescents that we moved from our old home. Compact florescents don't work in a lot of fixtures and have their own problems, but  they were the only efficient options at the time. However, in the last few years LED lighting has really come into its own, and we started slowly replacing all of the lighting in our home with LEDs. At this point, nearly all of our lighting is LED-based inside the house, including the can lights in the basement and kitchen where the lights stay on the most.

We also made a few other changes, including putting in a clothesline for use in the months where pollen isn't terrible and/or rain isn't an issue. There are likely are other factors contributing, but the weather was generally the same for these years and we didn't spend any extra time with all of the power turned off. Which is to say, this isn't intended as a scientific analysis of the impact of any particular method, just an encouraging note to anyone who might be trying to save electricity and the associated costs.

Here's the graph that matters. This is the amount of energy (kWh) used in a year, graphed by the last date in that year. Usage peaked around 19,500kWh in the year ending August 1, 2015. Since that time, usage has steadily decreased. For the most recent year (ending May, 2017), usage was down about 20% from the peak. That's pretty good return for some minor changes. There was some worry that the amount spent would not have a similar drop, since a portion of the bill is fixed and does not change with usage. However, the amount spent reduced just a bit more than usage (21% versus 20%), probably due to fluctuations in power pricing.


If anyone is interested in the numbers behind the graph, here are the daily power usage numbers pulled from those 4 years of bills. For most months, the usage dropped year-over-year, as the graph above would suggest. There are exceptions (I have no idea what happened in August, 2013), but the trend is obvious. Our usage is consistently down, year-over-year.


Unfortunately, the savings is going to impact the solar panel ROI since ROI will be based on what we were spending originally and our spending is down. We'll see how those numbers come out starting sometime next month, hopefully.

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