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The Voltage at My House — Summary and Details of Measurements

My House Voltage Measurements

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Current situation  —   During the first 14 days of August, the voltage at my house has averaged 124.94 VAC and was greater than the nominal voltage 99.8% of the time, based on 2,014 measurements.  The chart below shows the history of the voltage at my home so far during August.  Note the wild and almost out-of-control voltage swings on 9, 10 and 11 August, at one time reaching 129.2 VAC!!  The green line is the nominal voltage of 120 VAC. 


History of voltage in August 2019

Comparing the Months

What follows is a summary of the thousands of measurements I have made of the electrical voltage supplied to my home by Ontario's Hydro One provincial power utility, measured at one of my wall outlets, beginning in December 2015.  In the past, Hydro One has often supplied too much voltage, that is, significantly more than the desired, nominal voltage (120 VAC). 

Graph of monthly average voltages

The graph above and the table below will give you a good idea of what voltages we get from our wall outlets at my home south of Ottawa.  While some months have exhibited some crazy voltage behaviour, the voltages delivered during July 2019 have been the craziest so far.  See Last Month's Voltage for details. 

Summary Of Monthly Voltage Measurements
Month Average
Voltage
Range of
Voltages
No. of
Measurements
Dec 2015 124.25 VAC 121.0 – 127.2  135
Jan 2016 124.22 VAC 121.1 – 127.7  238
Feb 2016 124.17 VAC 121.1 – 127.4  283
Mar 2016 123.70 VAC  119.8 127.3  347
Apr 2016 122.68 VAC  119.7 – 125.7 272
May 2016 122.27 VAC 119.8 – 124.2 283
Jun 2016 122.51 VAC 120.5 – 124.4 246
Jul 2016 119.43 VAC 115.2 – 124.1 393
Aug 2016 119.44 VAC 114.9 – 123.1 317
Sep 2016 120.67 VAC  117.1 – 123.8 301
Oct 2016 121.12 VAC 117.6 – 124.3 344
Nov 2016 121.55 VAC 117.5 – 124.8 342
Dec 2016 121.91 VAC 118.7 – 124.7 373
Jan 2017 121.30 VAC 117.3 – 124.4 295
Feb 2017 121.86 VAC 118.9 – 124.7 224
Mar 2017 121.51 VAC 117.3 – 124.8 351
Apr 2017 121.44 VAC 118.4 – 124.6 316
May 2017 (1) 121.64 VAC 118.2 – 124.8 213
Jun 2017 122.52 VAC 118.1 – 125.7 222
Jul 2017 122.15 VAC 117.6 – 125.5 366
Aug 2017 (2) 122.59 VAC 119.2 – 126.1 219
Sep 2017 (3) 122.66 VAC 118.8 – 125.4 207
Oct 2017 123.24 VAC 119.8 – 126.6 456
Nov 2017 120.99 VAC 116.4 – 125.7 340
Dec 2017 122.17 VAC 117.6 – 125.3 359
Jan 2018 (4)
Jan 2018 (5)
121.6 VAC
122.00 VAC
115.6 – 124.9
115.1 – 125.9
269
3379
Feb 2018 121.87 VAC 116.8 – 126.1 4014
Mar 2018 121.96 VAC 116.4 – 126.0 4454
Apr 2018 122.18 VAC 116.4 – 125.6 4317
May 2018 122.79 VAC 118.0 – 126.8 4459
Jun 2018 122.16 VAC 116.6 – 126.1 4316
Jul 2018 121.34 VAC 115.4 – 125.9 4396
Aug 2018 121.58 VAC 116.2 – 125.5 4459
Sep 2018 123.00 VAC 117.5 – 129.0 4219
Oct 2018 124.23 VAC 116.9 – 128.8 4461
Nov 2018 120.32 VAC 112.9 – 127.0 4321
Dec 2018 121.38 VAC 113.5 – 126.5 4462
Jan 2019 123.12 VAC 117.9 – 127.4 4460
Feb 2019 122.83 VAC 118.3 – 126.8 4004
Mar 2019 123.24 VAC 119.1 127.9 4455
Apr 2019 123.64 VAC 118.9 – 126.9 4275
May 2019 122.28 VAC 117.4 – 125.9 4461
Jun 2019 121.31 VAC 113.1 – 125.7 4317
Jul 2019 121.96 VAC 113.9 – 132.6 4460
Aug 2019 (6) 124.94 VAC 119.5 129.2 2014

Notes — (1) Final results based on measurements for the first 22 days of May 2017.
(2) Final results based on data for the first 27 days of August 2017.
(3) Final results based on data for the last three weeks of September 2017.
(4) Final results based on data for the first 24 days of January 2018 using manual measurements.
(5) Final results based on data for the last three weeks of January 2018 using automatic measurements (note the increased number of measurements, now once each 10 minutes).
(6) Interim results based on data for the first 14 days of August 2019.

If your electricity is supplied by Hydro One, maybe you suffer from the same excess voltage, consistently and needlessly higher than 120 VAC.  Keep in mind that the average voltage should be near 120.0 VAC, although at any given time it might be anywhere in the range between 118 and 122 VAC.  That would be "normal" and acceptable, but voltages as high as 127 VAC (as I have measured) are definitely not acceptable, even though Hydro One might try to pass them off as "normal".  And an average voltage that is consistently higher than 120 VAC will cost you extra money that you could probably use for other things.

Average voltages within the range 118–122 VAC are acceptable and are highlighted in green.  High and low voltages within the range 118–122 VAC are acceptable and are also highlighted in green.  Voltages over 127 VAC are considered dangerous ("extreme" as specified by the Canadian Standards Association), are therefore not acceptable and are highlighted in red.

More detailed information about the voltage measurements at my house can be found here with separate graphs for each month beginning December 2015 and continuing up to the end of last month (updated monthly). 

A few words about my measurement method can be found here.  Some details and comments about the effect of the very hot weather during the summer of 2018 are found here.

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

General Observations about the Voltage

  1. the voltage tends to be higher at night than during daylight hours;
  2. the voltage tends to be lowest in the early evening;
  3. during Dec 2015 through March 2016, the voltages delivered to my home were much too high, and that is what I am complaining about;
  4. during July, August and September, 2016, the average voltage at my home was near normal, that is, near the nominal voltage of 120 VAC, and I have no complaint about that;
  5. however, since then the average voltage has gradually increased, and now averages around 122 VAC, still higher than it needs to be (see chart and table above).

Harmonic Distortion

For those who care, a recent measurement campaign during the last 8 days in April 2018 found that the average total harmonic distortion (THD) of the 60 Hz voltage waveform delivered to my home by Hydro One was 3.08%, based on 1,187 separate measurements.  Details are here

Got Data?

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