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Monthly Details of Electrical Voltage Delivered to My Home

Graphical Details of My Monthly Voltage Measurements

What follows are separate charts for each month showing the thousands of voltage measurements I have made at my wall outlet of the too much voltage delivered to my home and appliances by Hydro One.  The charts include a time series diagram (history), a statistical histogram of the voltage during the month, and a scatter diagram of voltage versus the time of day, for each month beginning December 2015. 

A general summary of all my measurements, with some up-to-date interim data for the current month, can be found here.  The monthly details below are presented in reverse chronological order, that is, most recent months first. 

If you have questions or comments about any of the information here, please contact me

July 2017

Voltages at my home moderated somewhat during July, averaging about 122.1 VAC.  Despite several spells of very warm weather, the range of voltages seen did not increase from previous months.  The average voltage is still higher than I would prefer. 

History of voltage during July 2017
Histogram of voltages during July 2017
Voltages at time of day, July 2017

June 2017

Voltages were significantly higher this month than they have been, in fact, highest since the end of that terrible (voltage-wise) winter of 2015-16.  The recent increasees definitely look like a trend!  See the chart on the summary page

Chart of voltage history, June 2017.
Chart of histogram, June 2017.
Chart of voltage versus time of day, June 2017.

May 2017

Voltages seem a little higher this month.  I hope it isn't the start of a trend.

Voltage history, May 2017
Voltage histogram, May 2017
Voltage at time of day, May 2017

April 2017

Voltages during April were about the same as during March, helping to establish a definite levelling off of the voltage supplied by Hydro One.  It will be interesting to see if this level of voltage can be maintained during the coming summer months when the system is stressed by the impacts of hot and humid weather. 

History of voltage, April 2017
Histogram of voltage, April 2017
Voltage at time of day, April 2017

March 2017

March showed a slight relaxation in the trend to a higher average voltage and the average voltage seems now to be stable at a value between 121 and 122 VAC.  Sure wish they had done this during the winter of 2015/16!  As noted in February, the difference in voltage between day and night is much less now than before. 

History of voltages, March 2017
Histogram of voltages, March 2017
Scatter diagram of voltage at time of day, March 2017

February 2017

February saw a continuation of the trend to rising voltages since last summer.  The average voltage is still less than 122 VAC but not by much (121.86 VAC).  I suppose that Hydro One hopes that I will become bored and stop watching them.  (As a confirmed data junkie, I am unlikely to do that!).  Curiously, the day/night difference is much less clear now than before (see the Time of Day scatter diagram). 

History of voltage, Feb 2017
Histogram of voltage, Feb 2017
Scatter diagram of voltage at time of day, Feb 2017

January 2017

Voltages observed during January 2017 were much better behaved than a year ago and were almost normal by comparison, averaging near 121 VAC instead of 124 VAC.  Whether this was due to some new customer-friendly policy at Hydro One or was dictated by some technical circumstance of supply and demand, I do not know.  Compare the three charts below with those for January 2016, further down. 

History of voltage, Jan 2017
Histogram of voltages, Jan 2017
Scatter diagram of voltages measured at time of day, Jan 2017

December 2016

Voltages during December continued higher than during the last summer but not as high as one year ago, during the winter of 2015-2016. 

History of voltage, Dec 2016
Histogram of voltage measurements
Scatter diagram of voltage versus time of day

November 2016

Voltages during November were again higher than the previous month, but not yet as high as during last winter. 

History of voltages during November 2016
Histogram of voltages during November 2016
Voltages at Time of Day during November 2016

October 2016

Voltages during October were somewhat higher than during the summer, perhaps due to the lower load on Hydro One's supply system (less air-conditioning and still not much need for heating).  The average voltage is no longer near 120.0 volts AC. 

History of voltage during October 2016
Histogram of voltage October 2016
Voltages at Time of Day, October 2016

September 2016

The lower voltage situation seen in July and August continued in September.  These voltages are very kind to my appliances and my Hydro bill, and I hope they will continue. 

History of voltage measurements during Sep 2016
Histogram of voltages during Sep 2016
Voltages at time of day, Sep 2016

August 2016

The lower voltage trend set in July continued during August.  You could see on the hottest days how much lower the voltage was than on cooler days.  There was a small but significant increase in average voltage around the 13th of August which continued for the rest of the month.  Overall, from the point of view of a residential customer, the average voltage was quite acceptable, and the lowest and highest voltages were also very acceptable.  Let us hope that this continues for some time. 

History of voltage measurements during Aug 2016
Histogram of voltages Aug 2016
Voltages at time of day Aug 2016

July 2016

What a difference a month makes!  Big changes!  Over a period of several days beginning on 02 July, the delivered voltage was brought down to around 119 VAC, even lower that it needs to be.  By the end of July, the average voltage at my home was between 119 and 120 VAC.  The diagram of voltage history, below, clearly shows the change at the beginning of the month and the subsequent lower average voltage compared to previous months since the beginning of July.  Due to this almost dramatic change I felt it necessary to take more measurements (385) than usual and, with this added "density of data", the daily shift in voltage is very evident in the Time of Day diagram, showing how the voltage is generally higher late in the evening and overnight and lower during the daylight hours.  As well, the wider range of voltages encountered during July shows clearly in the histogram.  Compare these three diagrams with those for earlier months to see the changes.  The present situation with probably continue until the fall when the average voltage will rise again. 

History of voltage during July 2016
Histogram of voltage during July 2016
Voltage at time of day during July 2016

June 2016

June was a continuation of recent months with an average voltage around 122.5 VAC (still significantly higher than the nominal 120 VAC it is supposed to be) and with less variation than during the winter months (see especially January and February below).  

History of voltage during June 2016
Histogram of voltages during June 2016
Voltages at Time of Day during June 2016

May 2016

As indicated last month, Hydro One has now moved to their 'summer voltage program', with a somewhat lower voltage than in the winter and with less variation in the voltage.  However, the average voltage at my wall outlets is still almost 2% higher than it needs to be and only occasionally dips below the nominal voltage of 120 VAC.  Two percent might seem small, but it adds up over time.  So, I am still paying for more electrical energy than my appliances need. 

History of voltage during May 2016
Histogram of voltage, May 2016
Voltage at time of day, May 2016

April 2016

A definite change has occurred!  As they do most years in the spring, Hydro One has lowered the voltage.  During April, the average voltage at my home fell to under 123 VAC instead of being over 124 as it was during the winter.  On one occasion I measured a voltage less than 120 VAC (actually 119.7).  As shown in the "history" chart, the voltage seems now to be more steady with less variation.  Of course, next fall the voltage will go back up again, as it does every fall. 

History of voltage in April
Histogram of voltage in April
Voltage at time of day for April

March 2016

Results for the month of March indicate much the same situation as in previous months, although there has been a small reduction in the average voltage being delivered, about half a volt.  What is needed, however, is a reduction of at least four volts, so this small change is of little practical value to rural customers.  There was also a period of unusual stability of voltage, around 122-124 VAC, during 16-17 March (a Wednesday and Thursday), but the variation in voltage soon returned to normal after that. 

History of voltage for March 2016
Histogram of voltage for March 2016
Voltage at Time of Day for March 2016

February 2016

During February 2016 the voltage at the wall outlets of my home was measured 283 times and the average was about the same as during December and January.  As before, the highest voltage was over 127 VAC. 

History of voltage during Feb 2016
Histogram of voltages Feb 2016
Voltage at time of day Feb 2016

January 2016

During the month of January 2016, I measured the voltage at my wall outlets 238 times.  The average was about the same as during December and the highest voltage measured was 127.7 VAC, again just within the range defined by the CSA as "extreme operating conditions". 

History of voltages, Jan 2016
Histogram of voltages, Jan 2016
Voltages at Time of Day, Jan 2016

December 2015

During the month of December 2015, I measured the voltage at my wall outlets 135 times, spread more or less randomly during the days and nights of the month, using a reasonably accurate digital multimeter and checked by comparison with others.  The measurements had a spread of 121.0 to 127.2 VAC, and a calculated mean (average) of 124.25 VAC. 

As expected from the calculated average (124.25 VAC), the peak in the histogram is between 124 and 125 VAC.  As shown in the "Time of Day" graph, the voltage tends to be higher late in the evening and over night, and somewhat lower during the day.  This tendency continued in the following months, as shown in the graphs above. 

History of voltage measurements, Dec 2015
Histogram of voltages, Dec 2015
Voltage at Time of Day, Dec 2015

Got Data?

If you have voltage measurements from your own neighbourhood and would like to share them, please contact me and I would be glad to exchange raw data and other results with you. 

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