Home Battery and IoTaWatt

So, I have had the IoTaWatt for about 8 months and I could not ask for a better supported product for my energy monitoring needs. Due to some of the storage and logging requirements, I send all my data from the IoTaWatt to a local EmonCMS server for dashboards and viewing; I also leverage the PVOutput tool.

I had a home battery installed about a month ago, but there was an issue with the transfer switch that needed to be replaced by the vendor. Nearly a month later they got around to fixing it and I have been three days without pulling any power form the grid. Yeah. The Powerwall 2 is about 14kWh of storage and can pull 7wh peak at a time. So I do not leverage my heavy loads while on battery (AC/Range) The house uses solar to power the home as well as top off the battery when I have sun. Once the house and battery have been satisfied, any remaining energy goes to the grid as an export. This is a limited home back battery system, so it required the new load panels be added which you can see in the image below.

The thin long panel on the left is my old main panel (load center). The install for a limited back required a new main breaker be added (middle center) along with a transfer switch (right top). The battery and solar inputs are brought into the lower left where you can see the Tesla connection.

With the new panels and the moving around of my mains, I had to mount a new box (lower center) which is for low-voltage cables and my IoTaWatt device. Here, because of the great CTs @overeasy provides, I can reach every location and have room to spare. Love the longer CT cables.

Today (~3:30pm) I have had a good day of sun and the battery which was at 25% when I woke up, we fully charged by 11:30am. I have few things I need to work out regarding the power for PV Output as you can see in the graph below. My “Power Used” seems to include my battery export (charging) and you can see the drop off around 10:30am where it begins to trickle charge the battery. But as you can see, the “Power Used” follows the “Power Generated” which I need to look at as it appears to include the battery export.

What I like to see below is the great day of Sun and how it is sent distributed. I would not be able to do this without the IoTaWatt unit. All numbers below are DAILY numbers which reset at midnight my time. So one can see that the home today has generated 42.27 kWhs so far. Home kWh and Consumption show the homes usage for the day. Grid cost shows the fee I pay to the grid, negative numbers are good. :slight_smile: I added the Battery Import (discharge) and Battery Export (Charge) values so I can track how much the battery is used and charged from my solar. The battery will not charge from the grid as some system may be configred. So, only the sun will maintain the battery volume. Export kWh is specific to Grid exporting.


One more fun chart from the IoTaWatt as well.

Below is an image of my EmonCMS server dashboard with battery in the lower right showing a good 100% charge ready for the night I have also added a “Battery” dial in the top center to show negative (charge/export) or positive (discharge/import). All the data here updates every 10seconds which I love.


I think one of the most impressive things here is the way the Powerwall control seems to be able to use every available extra watt to charge.
As we speak there are some open discussions going on at the OEM forum concerning “diverters” and the openEVSE variable charge based on Emoncms MQTT outputs. None of them look anything like this. Powerwall seems to have done it right. No big surprise after watching spaceX landing like Flash Gordon.

I guess you will need to decide if the powerwall is just another load (reversible), or part of the supply-side and integrate the numbers appropriately. It is a new breed.

Thanks for the update.

Yes sir, I was also impressed that all my excess energy goes first to satisfy the battery and as the goes into trickle mode at around 96%, it is interesting to see the inverter begin to step down and begin exporting to the grid. I was impressed as well and will be monitoring it more as today was the first full one after making some tweaks.

Today I use the same configuration as the Grid with negative bring Export/Charge and positive being Import/discharge like a grid main. I think I need to find out to remove it from the “Power” setting with PVOutput which I have made changes for EmonCMS. I may have to do a custom input or change it in my setting to ignore negative power as this is not really “usage/consumption” but exporting.

So, that section you circled (which is cool) should not register that as power consumption but exporting to the battery when it is charging. That is the last part I think I need to work out to get things back as they were before the battery was installed.

Agreed, new waters here, but I’m loving it. I have to also laugh that I live in a small town like yourself and our electrical inspector never saw one or knew what a Powerwall was. Fun to chat with him and the Tesla rep about the tech and use case. Oh yea, he also liked the not only the Tesla panel installs, but my energy install as well. One for me. :slight_smile:

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I think I found my issue with PVOutput which just required me to add the Battery1 and Battery2 inputs to the formula.


I will see how it goes Thursday when I start to charge back up (if there is Sun).

It shows just how versatile the IoTaWatt product is.

I may have my PVOutput consumption incorrect as this messed with the Energy Generated as shown below. Maybe It will correct come next day. As this is how I’m doing “Consumption” on the IoTaWatt output. Strange as it might be a formula on the PVOutput side in calculating this value.