Looking to buy an iotawatt

looking to purchase unit…not sure really where to start…i have 400 amp service and a 100 amp sub panel off one of the 2- 200 amp panels that goes to a detached garage…im trying to to see what items are eating up power…we have 2 geothermal systems 2 ton upstairs and 3 ton for main level…square footage of house is around 4300 sq feet…

any advice where to start and what to but would be greatly appreciated …


The best place to start is with a line drawing showing the two 200A panels, the sub panels and how they are connected to the 400A service. Also labelling the three panels, what loads you are interested in in each of the panels, and whether the loads are 120V (one breaker) or 240V (2 gang breaker).

A good hi-res picture of the panels is usually helpful, both with and without the covers.

60,000 BTUs for 4,300 sq ft isn’t too bad in northern climates and indicates a fairly efficient house, but in the south it’s all about the AC and latent heat, so what is the climate?


I live in Indiana sooo in winter can get pretty cold…my back up all electric coils for the down stairs 3 ton geo rarely kicks on…
we are a family of 4
husband…wife…2 boys 13 and 11…they are home schooled so they are home all day also

Upstairs the 2 ton geo system is backed up by natural gas 98+ efficient furnace

id assume my big draws are:

Hot Tub which sets out side …hot spring is manufacturer
Salt water fish tank 75 gallon…has led lights but circulation pump that runs all the time
electric dryer
electric stove

i have attached some pics…just looking for phantom draws or what is eating up electricity and what we can turn off to be cost effective and smart

2ND 200 AMP



Hope this helps a little


Hi Wade,
You’ve got a lot going on there. Didn’t mention the GENERAC. How does that contribute?

Fundamentally, one IoTaWatt can monitor 14 circuits. A 240 volt (double breaker) circuit that uses a neutral wire (“three-wire load”) requires two or one if there is enough wiring slack to pass one of them through the CT in the reverse direction. There are other ways to combine things, but without getting into specifics, lets talk about the overall strategy.

I’d recommend monitoring monitoring each of the three panels in their entirety with CTs on the mains. That will require six inputs to the IoTaWatt leaving 8 for individual circuits.

The larger loads are:

Panel 1:


  • AC
  • Dryer
  • Unknown 100A
  • Sub-Panel (measured separately)

Panel 2:

  • Water Heater
  • Hot-Tub
  • Garage

Sub Panel:

  • Geothermal Up
  • Geothermal Down
  • Geothermal Water pumps
  • Electric Heat Elements
  • Tesla Charger

You don’t need to get this right off the bat.
Initially, you will be able to breakdown the usage by panel and, to some extent the 120V loads in each panel will be divided between the mains so you will be able to narrow any large users down.

I’ll need a picture of the inside of the sub-panel to know what’s required and possible in there, especially since that’s where the likely suspects are.

You will need one or two CTs for the Hot Tub.

Then depending on the sub-panel layout you should be able to monitor most of the circuits in there.
The Tesla is probably straight two-wire 240V so one CT.

UPDATE: Didn’t mention but hot tubs can be a major drain in the winter. If yours has good insulation around and under (talking well molded thick foam) you have a chance. Evaporation is the whole ball-game here. Even the best fitting covers don’t compare with a well fit floating “bubble-wrap” type cover inside to stop evaporation. You don’t need an energy monitor to see if that’s the case.

Keep track of how much water you need to add. Ball park calculating a gallon of water weighs about 8.4 lbs. You lose about 1000 Btu/lb of water that evaporates (latent heat). So every gallon lost is about 8,400 Btu. 3412 Btu/ kWh means each gallon evaporated loses about 2.5 kWh of heat which must be replaced (plus the Btus required to heat the replacement water to standby temp.).

I’ve also seen where the pumps can use as much as 500W and sometimes run for 12 hours or more just to filter. That’s 6 kWh.

The white taped breakers are not in use…those items have been moved to the generac circuits …the heat pumps in panel A on left are not used …they are shut off as well as the disconnects outside…

so any white taped breaker is not powering anything


I saw that, so no heat-pump in panel 1. I think the rest is all the same. Is the second 100A breaker in panel A feeding the Generac transfer switch?