Powerwall 2 constantly exporting about 100-130W to the grid?

[rgledhill]

Hello all,
I've had my Powerwall 2 for a few days now, and I've noticed that even when the house is set to run off the battery (which is all day from 05:30 onwards), my utility smart meter shows a constant export to the grid of 100-130W. If I "go off-grid", then this disappears to 9W which is just calibration and inaccuracy. However 120W (the average I see) is a problem in my eyes, because over the period of the daytime hours, it could export up to 2kWh, which I don't get paid for and then have to charge up again - or worse, the battery depletes before the end of the peak rate and I have to pay full rate when it should still be using the battery!
Any ideas? Do others see the same thing? I realise that in order for the battery/inverter to power the house, it needs to put out a slightly higher voltage than the mains input, but this seems excessive. I'm wondering if it's to do with cable run length to the CT clamp, which is about 20m...
Thanks
Richard

 

[JohnRatsey]

What does the Powerwall think it is doing? Does the Tesla app also show this constant export? Alternatively log into the gateway and see what that shows.

There used to be a problem with some smart meters recording power inflow even when there wasn't any. Perhaps you have the same in reverse.

 

[rgledhill]

Thanks John. The Powerwall reports 0W to/from the grid so it seems oblivious to the export going on; however there definitely is current flowing out into the grid, since when I go "off grid", it drops to effectively 0W. This is somewhat annoying as it will eat up to about 15% of the battery each day!

 

[yblaser]

Just for reference when I'm on battery power my meter bounces around in between ±20W so is pretty much averages out to zero. I'm using the built in CTs in the gateway and this is in the US. What you are seeing seems a bit excessive. Have you brought this up to your installer?

If you electricity service provider provides daily electricity usage values it might be interesting to plot those versus what the Tesla app thinks your daily grid usage is to determine if it is off by a fixed percentage or not.

 

[Vines]

Thanks John. The Powerwall reports 0W to/from the grid so it seems oblivious to the export going on; however there definitely is current flowing out into the grid, since when I go "off grid", it drops to effectively 0W. This is somewhat annoying as it will eat up to about 15% of the battery each day!

It sounds like the CT's for something are not reading accurately. Call your installer out to fix it.

 

[JohnRatsey]

I agree, call the installer. A clamp meter on one core of the mains cable will quickly reveal whether or not power is flowing. If it is then there's the need to understand why. It if isn't then sign up to a tariff which pays for export!

 

[Cmdr Powell]

I have a similar problem but the other way up. My meter shows import from the grid when the PW is supplying all of the power.
I looked around and found an blog entry by Octopus Energy The perils of being a tech innovator, working with a tech innovator that shows (in great detail) that there is an interaction between my meter and the PW. This causes the meter to read incorrectly.
It's only one specific model of the meter from L+G

Octopus supply my power, so I dropped a note to the author of the article and he's arranging for the meter to be replaced and any overpayment to be refunded.
If you have the same meter then you may have the same problem with slightly different symptoms. If so then contact your supplier and see if they'll swap out the meter.

 

[jgleigh]

Here's an old thread. Could be a wiring issue, firmware issue, or CT issue.

Solar pulling from grid vs Powerwall [in small amounts]

I've had solar 7.2kw and the Powewall+ installed last month (August). Everything has been excellent, zero issues until today. I got PTO yesterday and activated exporting from the app yesterday afternoon. I didn't notice this issue then. Today I noticed every few seconds the system will pull...

teslamotorsclub.com

 

[rgledhill]

Many thanks everyone - sorry for the delay in replying, we've been away for a week.
I've contacted the installer who are going to get someone to take a look tomorrow when they do the final electricity installation sign-off certificate, so we'll see what they say.
Dependent on that, I'll contact Octopus Energy as I'm with them too.
The Tesla app itself shows 0kW to/from the grid, but the Octopus app shows "Live use" of -111W at this moment. I'll go and have a read of those threads too.
Many thanks!

 

[jgleigh]

When the installer or electrician is out, you should have them measure the current on various wires to see where the stray power is going to. The CT clamps aren't perfect and can't react instantly but should be 10s of watts of leakage, not 100s of watts of leakage. Could also be a mis-wire on the CT itself where it's bridging Phase A and Phase B.

 

[rgledhill]

Well, they came out and checked things thoroughly and couldn't find anything obvious. They put a CT clamp on the actual live cable coming into the house and it measured around 1.2A being exported, which would convert to around 260W - which also doesn't correlate with the ~100W that the smart meter is reporting! Also, the Powerwall was still only reporting 0.1-0.2kW discharge, which matches what the house idles at.
Looking at that blog article, it says that basically the Landis+Gyr smart meter was reading the inverter noise generated on the mains from the Powerwall. Well, I have a L+G smart meter, so I'm wondering if the same thing is happening here... I'll drop Octopus a line to find out.

 

[rgledhill]

Octopus are brilliant! Thank you for the link @Cmdr Powell, that was spot on! I dropped Octopus an email last night and the author, Phil, came back to me this morning confirming that the issue is with that specific model of Landis + Gyr smart meter, and they're going to replace it.
Thanks everyone!