Running two base units in medium-sized home?

Hi all,

I’m excited to have discovered IoTaWatt and am seriously considering jumping in. My medium-sized US home has a 200a service with 25 circuits running throughout the house. It makes sense to me to monitor them individually (more data = better, right?) so I’m looking at buying two base units to accommodate as many CT’s as possible.

My question is: I see almost nobody on the forums doing more than one base unit, so I just wanted a sanity check. It seems most people here are content to just monitor the mains, plus put CTs on a few major circuits, double up if they need to, and leave the difference as “unknown / baseline”. Am I a real outlier for wanting data on each circuit? Is it hard to fit that many CT’s in a standard panel box?

To that end, I’ve put together a shopping cart that includes:

  • 2x base units
  • 2x USB power supplies
  • 2x AC reference transformers
  • 2x 200A CT’s (assuming I can split their signals into the other base unit)
  • 24x 50A CT’s

Subtotal: $477.75

And I’d buy one large wall mount enclosure to house it all in.

My plan would be for both units to write data to influxdb so that I could see a UI with combined data in Grafana / Home Assistant.

Photos in case they are helpful:


Allen, I was in the same boat when I first started and I will say that your setup and shopping list looks good to me. If you want to collect everything, I would say go for it, and you will not find a better and well supported product than this one for that job.

I’m a data guy myself and to me more data is always better. :slight_smile: What makes things a bit more difficult is knowing or caring what might be on some of the 120v branch outlet/lighting circuits. I have many of my circuits in an older home that are for things like upstairs outlets or general lighting, but over time other type of things were connected to these circuits as well; ceiling fans. It would be nice if one circuit was dedicated to a room in the home, etc. Again, my being in an older home maybe they do break things up better in a newer install (your panel looks too clean and I would assume newer home).

As you begin to monitor your circuits, you will notice many of your low load one are quite static or not heavy energy usage, so when you compare them to the mains they are really quite small. Things like lights, plugs, bathroom fans, and the like can be quite boring to map over long periods. Things get a bit more interesting when you can see heavy load circuits and the amount of energy they use. Pumps, motors, heating elements and the like (240v circuits) are quite interesting when compared to your overall energy usage. If you have a single IoTaWatt and have to be selective, this is where it makes sense to monitor the heavy load items which can more easily be determined and controlled from the smaller ones. I used to monitor my boiler (240v load) but it is an oil burner which uses electricity to start but once running, there is no energy being drawn. So, I could see it start when the heat or hot water went on, bit again this seemed rather static over time.

For me, the important data, which has changed a bit from then to now, has been the mains, my solar, and I also have a solar battery. I want to make sure I know what I generate with my panels, export/import from the grid, export/import from the battery and the other high load circuits which may impact these three key figures. In the summer I like to see my AC usage and if this is drawing from my solar (day) or battery (night) when I might instead turn it off or higher.

For me it is about things like my dryer, well pump, range, two sub-panels, solar, mains, and battery. From these I can often determine other usage in the home. My dish washer and small counter oven are simply on my 120v kitchen circuits, but when I subtract my main loads from my total usage, I can see when these items are on and drawing power. Much like a hairdryer or curling iron, etc.

Not that it would add too much, but also be aware that you will need to have the storage as well for all this data you will collect over time. I would be interested to see what other have to say. I’m just at 1 year with the IoTaWatt and I can say that over that period I have settled in on the Items I’m interested in and have a few open ports in the device, but not sure I really case to collect the data from my smaller circuits.

I would say that @quella did a pretty good job of answering, I will only add two things:

The picture of your panel does not include labels, but I see you have quite a few 240V 20A breakers. That’s usually electric baseboard heat. If so, those can each be monitored with a single 50A CT, or up to three could be combined with a single 50A CT.

The other point I will make about many branch circuits is that LED lighting has been a game changer with respect to power usage. There was a time that a dozen lightbulbs would be on using close to 1,000 Watts. Now that’s 100 Watts. So what used to be a big part of the total load is gone now. When these circuits are combined, they have a very low baseline and any transient loads like hairdryers are easy to pick out, and don’t amount to anything in the big picture anyway.

I’m going to address the sizing of the CTs in the other post about that this morning.

I have two IoTaWatt units. I started with one. Previously, I had a single ecm-1240 (from Brultech, has 7 inputs).

Monitoring just the mains will provide an abundance of data, but it is harder to make sense of it and do something about it. If you are interested in learning more about utilization monitoring every circuit will provide you with lots of data, but most of it will be really boring and not very valuable.

Finding out your base load (the minimum power used, ie stuff that is on 24hr/day) and figuring out how to reduce it, is one thing that you can do with only the mains monitored. But, having more circuits monitored makes it easier.

Influx doesn’t do math across streams (but the new stuff still in beta might make this possible) so you have to do that before it gets there. I use NodeRed for some things (like the efficiency of my dehumidifier).

Anyway, I think having two is better, but the math is harder. One is probably going to get more than enough data to keep you busy for some time.

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Thanks everyone for your helpful replies! I spent most of yesterday with a friend testing each outlet / switch to see which circuits are which, and I think I’ve decided that yeah for the extra cost of another unit I’d enjoy having more data.

In case anyone is curious, the house is from 1899, with a mix of knob & tube wiring, 1970’s era cloth ungrounded 2-wire, and a little bit of modern romex. I spent yesterday with the electrician checking each outlet and our plan is now to pull a lot of fresh circuits to modernize as much of the house as possible. While he’s at it I’ll have him setup the IoTaWatt :slight_smile:

To minimize the footprint of the box, I’m considering ‘stacking’ the two base units on top of each other inside the box. If I need to access the rear one for some reason I can always temporarily disconnect the CT plugs and remove the front one. Is that a problem for any other reason, like ventilation?

Thanks again!

I like the stack idea. Maybe consider using two threaded posts so that the upper unit has a nut on each side of the mounting flange. Be sure to post pics when done.

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