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SMETS2 and reactive power.
Posted: Sat Oct 22, 2022 2:16 am
by Tinbum
This morning I was just looking at a slight discrepancy between what power I was reading and what power my display was showing and started thinking about reactive power and whether the SMETS2 meters measured it.
Came across this interesting tread that may be of interest to Tesla owners.
https://teslamotorsclub.com/tmc/threads ... rs.188061/
Re: SMETS2 and reactive power.
Posted: Sat Oct 22, 2022 8:13 am
by Oldgreybeard
Tinbum wrote: ↑Sat Oct 22, 2022 2:16 am
This morning I was just looking at a slight discrepancy between what power I was reading and what power my display was showing and started thinking about reactive power and whether the SMETS2 meters measured it.
Came across this interesting tread that may be of interest to Tesla owners.
https://teslamotorsclub.com/tmc/threads ... rs.188061/
Yes they do measure VA as well as watts. Before smart meters, domestic electricity billing meters only normally measured true power (watts rather than VA). Smart meters measure both, and hold the readings in separate registers. At the moment they are required (by law, I believe) to only bill based on true power, the same as all other electricity meters, so there should be no difference between either type of meter.
Commercial consumers do often get billed for VA, rather than watts, so it pays them to correct the power factor of their heavy loads in order to get watts closer to VA.
It is worth remembering that electricity meters don't have to be super accurate for billing, and will often have errors of a couple of percent or so. They are allowed to have an error, as the law states they have to read between -2.5% and +3.5% of the true energy delivered, I believe
Re: SMETS2 and reactive power.
Posted: Sat Oct 22, 2022 12:10 pm
by nowty
The official accuracy of meters are only above a certain minimum value so as battery inverters attempt run as close to zero as possible, they don't work too well. Some inverters give you the option of setting a + / - fixed offset.
I have to set a -9W (constant exporting) offset to my SMA Sunny Island to get my smart meter to read zero.
In comparison, when I used to have an electronic but non smart E7 meter I could set my battery inverter to constantly import around 15W without the meter registering anything.
The Tesla Powerwall incompatibility with one type of meter has been well documented.
https://octopus.energy/blog/perils-work ... nnovators/