Sense voltage readings

In the sense app, under settings, if you click on “my home” then “sense monitor” it shows two values for voltage. What do they represent?

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(Link) - The two principal properties of the electric power supply, voltage and frequency, differ between regions. A voltage of (nominally) 230 V and a frequency of 50 Hz is used in Europe, most of Africa, most of Asia, much of South America and Australia. In North America, the most common combination is 120 V and a frequency of 60 Hz.

Columns depict the left and right side voltage readings:

Thanks. I know a little bit about AC electricity, but my question was why there are two values shown. What do you mean by left and right side?

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Most North American homes are supplied by and wired for split phase AC electricity, mainly to allow us to have both 120V and 240V circuits in our house. The two numbers are for the two different phases, or legs as they are often referred to.


And not to complicate issues BUT:

Not all supply voltages are 120V + 120V = 240V

As @kevin1’s reference points out, 240V is available because the voltage phases are at 180 degrees.

Like many urban panels, my supply is coming from 3 phases, of which my panel has 2!
So in my case I have 120V + 120V = 208V!

Sense auto-magically accounts for this although strictly speaking I imagine the phase-related disaggregation algorithm at the DSP is less happy due to the smaller dataset of 2-of-3-phase users.

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