Out of curiosity I set up a properly isolated DVM to log my local AC line voltage over a period of approximately 34 hours. The results were both interesting and surprising.

The above is a plot of AC Line Voltage vs Time.

Interesting points to note:

• The lowest voltages occurred from about 17:00 – 23:00 local time (120vac and below)
• The highest voltages occurred from about 23:00 to 05:00 local time (121vac and above)
• The data set comprises over 6000 observations (one every 20 seconds)

Distribution Histogram:

• Vmin = 115.9 vac
• Vmax = 122.1 vac
• Vrange = 6.2 vac
• Vmean = 120.04
• The data are not normally distributed

Line Voltage Plot Shaun Merrigan