Help me figure out what equipment/hardware to purchase

I’m still trying to wrap my head around IoTaWatt and all it has to offer. I know this is the energy monitoring hardware I want to buy I’m just unsure which components and/or kit I need.

  • I’m in North America, Texas USA
  • No Solar
  • Have a main and subpanel (pics below)
  • Will be installing a 240 EV charger in one of the available slots on the main panel soon (probably have the same electrician do this install and that)


  • Ideally want to monitor the big energy suckers which include:
  1. two HVAC units (mostly AC usage in the summer)
  2. pool equipment
  3. EV Charger (once installed)
  • Would also like to monitor the smaller items like lights, fridge, washer/dryer etc.

My main question is should I just focus on the main panel to start? Or is it not that much more from a cost point to also hook up the subpanel?

Anything else to bring up that maybe I’m overlooking or not considering?

Also location of the panels may be something you’d all like to know…
The main is located outside on the exterior of the garage. The subpanel is about 25 ft away inside the garage along another wall.

Thanks a ton! Looking forward to reading some of your replies =)

Your service is 300A. Probably OK with 200A mains CTs but could be something I don’t see.

Can’t read the subpanel breaker capacity, but guess it’s <= 100A. You can monitor the whole subpanel usage from the main panel by putting CTs on the two poles of the breaker. To monitor specific loads in the subpanel you will need to either extend the CT leads or add another IoTaWatt. If the EV charger is connected to the subpanel, you may want to do that.

The loads you mention: A/C and pool appear to be fed from the main panel, so that’s OK.

You will need to decide if you want to mount the IoTaWatt in a weathertight box on the exterior or inside on the other side of the wall. The electrician will probably have an opinion on that. Depending on the subpanel capacity, he may want to connect the EV charger to the main panel anyway and so would need to lead the cables through the wall.

Yep the ev charger will go in the main panel. So I think you bring up a smart idea to have him run the wiring at the same time to the other side of the wall and interior of the garage.

If I want to individual monitor the big items like pool, a/c and ev charger what do I need to buy? And can I also monitor the smaller breakers?

FWIW, the main is actually just 150A. The extra poles are just for connecting to the bus fingers as they are only rated for 100A each.

I would personally go for 2x200A and 12x50A CTs, and look at what is drawing power and pick circuits in the main panel that way with the electrician. Get a second unit for the sub panel if you think there is anything interesting there that the main doesn’t give you.

Everything I see can be monitored with 50A CTs except probably the sub-panel that would need 2 100A. So mains 2x200, sub 2x100A and then 10 50A.

Great thanks all

How long is the 120V power supply cord? It doesn’t say anywhere but I believe I can reach a plug that is on the other side of my fence maybe 6 ft away…?

You would need a power strip.