What does the Gateway api actually report?


#1

I posted this in a general Questions thread but the Powerwall forum is probably more appropriate.

In my continuing investigations into why my Smart Meter appears to be over-reading or logging reactive power, I have noticed that the the gateway api raw data download “site” values are sometimes positive and sometimes negative. e.g.
instant_power":-8,“instant_reactive_power”:307
The “Load” values are always positive.

The api downloads “instant” readings. Does it depend on where in the AC “sine wave” it takes the reading, i.e. could it hit and return a value in the the negative part of the cycle? Or is it actually recording export when there is a negative value?

We do know that the Tesla Powerwall both imports and exports small amounts of power while supplying battery power to the house and maintaining the AC-DC inverters “'ticking over”.


#2

Mike,

It would be very unrealistic for any typical meter to report true instantaneous values of a power waveform. Meters will typically report instantaneous RMS values. Instantaneous waveform values just aren’t useful for energy monitoring.


#3

That’s what I would presume and hope. So I assume voltage and current are integrated over some period. I presume a digital multimeter does the same thing for AC voltage and the reading it gives is 0.71 x the peak absolute value. In that case am I right in assuming that the negative instant power values reported are real export values? They seem to change from positive to negative every few seconds.