Observations about electricity usage…

I’ve had a long-standing entry on the Recent News page stating I’d provide an update on energy usage at the Byrne Residence. With the heating/cooling systems functioning rather consistently for over a year now, (see earlier posts here and here, as well as one or two mentions on the Recent News page), I felt it made sense to sit down and do a comparison between two 12 month periods vs. the single 13 month rolling comparison I did a little over a year ago.

First, a couple of notes on the conventions you’ll see used in the two graphs below:

  1. The dates without any data are reflected with ∅, (there were five of these occurrences after the meter was installed on February 9th, 2012 – four in November 2012 and one in January 2013, but none since then).
  2. The temperatures shown are average daily temperatures in Fahrenheit.
  3. If I had to average temperatures to fill a gap, they are shown in both bold and italics, (there were three of these occurrences – one in August 2012 and two in October 2012, but none since then).
  4. The color key for temperatures is blue for cooler temperatures, (with the darkest blue being at, or below, 32 degrees Fahrenheit), 72 degrees Fahrenheit is represented by white, and temperatures at, or above, 90 degrees Fahrenheit are deep red.
  5. The color key for kWh per day is green for the lowest values, (meaning values below 10 kWh for the entire 24 hour period), yellow for values hovering around 50 kWh for the entire 24 hour period and red for values at, or above, 100 kWh for the entire 24 hour period.

Next, a few observations about the 24 months of data in aggregate:

  1. Total usage from July 1st of 2012 to June 30th of 2013 was 20,200 kWh. Total usage from July 1st of 2013 to June 30th of 2014 was 19,600 kWh, or about 3% less.
  2. The average daily usage for these same two periods was 55.5 kWh and 53.7 kWh, respectively, or about 2.9% lower for the more recent 12 month period.
  3. I did a little research into temperature and precipitation levels captured at a nearby weather reporting station located less than a mile from the Byrne residence. Between July 1st of 2012 and June 30th of 2013, the highest recorded temperature was 109.3 degrees Fahrenheit, lowest recorded temperature was 24.6 degrees Fahrenheit, annual precipitation of 15.01 inches and an average temperature of 71 degrees Fahrenheit. Between July 1st of 2013 and June 30th of 2014, the highest recorded temperature was 106.8 degrees Fahrenheit, lowest recorded temperature was 30.2 degrees Fahrenheit, annual precipitation of 9.78 inches and an average temperature of 71.3 degrees Fahrenheit.
  4. I also dug back into our records to see when we were at the Byrne residence and for how long. Again, the usage patterns were quite similar – our longer stays were at the same time of year and durations of each stay were similar, (modulo a small number of days in total).

This graph depicts July 1st, 2012 – June 30th, 2013:
The same 12 month period a year later, (July 1st, 2013 – June 30th, 2014):

Now, on to my observations, (starting with July 2012):

  1. I returned for the Labor Day weekend in 2012, so you see an uptick in energy usage in early September 2012 while I was there.
  2. We confirmed we had issues with the heat pumps in mid-December 2102, and you see evidence of that on December 16th.
  3. We returned in mid-January 2013 to a cold snap, and again experienced higher usage due to efforts intended to warm up things inside.
  4. In February 2013 we installed four brand-new American Standard heat pumps and one The UNICO System® air handler, so the spike on February 20th and 21st reflected the testing done during, and immediately after, installation of these new units.
  5. If you compare the cooler months of 2012-2013 to the cooler months of 2013-2014, you see less energy being used – I believe this is largely due to the simple fact we had properly functioning systems as well as warmer temperatures.
  6. Comparing January through March of 2013 to January through March of 2014 illustrates the importance of having properly-functioning equipment. …it also illustrates how moderate temperatures were this spring when compared to last spring!
  7. By the time we reach April, there isn’t much of a difference in terms of usage when you compare this year to last year.
  8. May reflects an uptick due to the number of days the house was occupied, as well as warmer temperatures, (when compared to last year).
  9. June repeats the April trend – slightly less usage this year when compared to last year, but not by a large amount.
  10. In mid-June 2014 we changed the wiring for all four Nest Learning Thermostats at the Byrne residence, after our HVAC specialist noticed what he felt was aberrant behavior – specifically the heat pump reversing valve was, in fact, reversing every time the thermostat signaled it was time to shut off after the desired temperature had been reached while the system was in cooling mode, (this wouldn’t be aberrant if the system was in heating mode). Nest Technical Support recommended the addition of a 24 volt common power source, effectively keeping the thermostat energized at all times. Once we made this straightforward adjustment, the aberrant behavior disappeared. It’s too soon to predict whether or not we’ll see a reduction in the consumption of electricity because of this change, but we’re hoping we will!

I will continue to track utilization of both electricity and water at the Byrne residence and post my observations periodically, (likely once a year, unless something unusual happens).

February 2016 Update:

I’ve made several small changes to the Microsoft Excel worksheet I created in 2012, so I thought it might make sense to post an updated version of the two 12 month periods reflective of those changes.  Specifically, you’ll see total kWh used by month at the bottom, as well as an average of the average temperatures, also found at the bottom of each month.

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