One of the displays that the smart meter PG&E installed in my home last month is a voltage display, which shows the total system voltage entering my structure from the power pole. This number fluctuates by 5-7 volts each day, which got me mildly curious but it was the supposed accuracy of the meter that really captured my attention so today I took my power panel apart and put a volt meter on the lugs just on the other side of the meter, giving me a reading just adjacent to the meter, about 10″ of 2 gauge cable away from the meter.

The meter is reading 239.3 volts energizing my home but the volt meter (which is relatively new and of pretty good quality) shows 235 volts coming in. I suppose you could get some voltage drop to the lugs but that is a pretty short distance to experience 4 volts.

If there is a technical explanation for what is happening, something other than my volt meter is wrong, then I’d like to hear it but simple readings like this do begin to throw up question marks about how accurate these meters really are.

UPDATE: I just received an email response on the accuracy question from someone who is intimately familiar with this technology, but because I have not asked for permission to publish the explanation with attribution I am doing so while maintaining the anonymity of the person who sent it to me. I have no reason to doubt their intent or expertise so at face value I shall take it.

I just verified that the meters are very accurate. Within 1-2% or better, the multimeter is most likely within 1-2% so you are talking about a difference of

Max =4.8 volt difference at 2% per unit.

If the meter is +- 2% and the VoltMeter is +- 2% then this can easily explain the difference.