Recommendations for Energy Use monitoring of appliances?

What’s a good approach for monitoring energy use of in-home appliances? I’m wanting to track down heavy users, “phantom loads”, etc.

How can I use OpenEnergyMonitor to monitor hard wired appliances, like a hot water heater, mini-split heat pump, well pump, etc.

I’ve used a Kill-o-Watt for ad hoc sampling of socket appliances, have programmed Arduino for other situations, and read some of the Guides here – including the “Use in North America” a couple times – but I’m not finding examples or recommendations for monitoring appliances.

Try a search on “sonoff” as that is one way to do it. Also search the forum for “appliances” and you will find other info such as…


Maybe I should not have used the word “appliances”? if that usually implies low load circuits. Sonoff looks like an option for low amperage devices, no? When I searched, there were concerns for circuits >15amps. … actually the Sonoff Wiki has a spec for the original Sonoff POW with sampling upto 16amps.

I meant that I’d like to monitor separate circuits that have dedicated loads in addition to the whole house
In case USA appliances have different specs/loads than in the UK, the monitoring I’m looking for is:

dryer = 240V @ 30amps
oven = 240V @ 40amps
minisplit = 240V @ 50amps
hot water = 240V @ 30amps
well pump = 120V @ 15amps

Each of the above are on a separate circuit coming off my home’s main panel.

Can I use Emon devices to monitor these? With their individual circuit/load data logged in separate graphs? Maybe the answer is an obvious “yes” but I’ve just not digested what the docs here are saying :slight_smile:

If you can safely access the cables on each circuit to add a CT then yes you can, but you’d need to buy 2x EmonTX (each one can do 4x circuits), or 1x EmonPi (2 circuits) plus an EmonTX plus power supplies etc.

@Bill.Thomson is US based so might have another slant.

Following on from Brian:

An emonPi will monitor (say) your two main incoming cables and run emonCMS, giving you the graphs and records. Fig 2 or Fig.3a on the N.America page is the arrangement for the main incomers.

Then for each 240 V circuit, you need only one c.t. on one leg - assuming you’re prepared to accept a minor inaccuracy because the control circuit will be run off 120 V so will take a very small current from one leg only. Fig.4c on that N.America page is the arrangement, and it doesn’t matter which leg you put the c.t. on.

Therefore, to monitor 5 separate circuits plus 2 for the whole house (which will catch everything else as well), your most economical solution is 2 × emonTx plus an emonBase (that’s an emonPi without the energy monitoring part, but still with a radio to receive the data from the two emonTx’s).

Yes, you can have each c.t. logged separately, and you can do maths before you log the data - so one graph could be the combined house power on both legs, for example. Another could be the imbalance between the legs - though I’m not sure whether that would be helpful :thinking:. You’ll need to do some maths anyway for the 240 V circuits - to double the power you measure - because you’re only picking up half the voltage.

Welcome to OEM!

The “main incomers” Robert spoke of are your Service Entrance Wires.
IOW, the wires that feed your load center. (circuit breaker box)

Robert, Brian, and Bill,

Thank you all for elaborating on which devices could do this (2 x EmonTx + EmonBase, EmonPi, CTs) and on how to setup.

I’ll do more reading.


I recently discovered an alternative to Sonoff made by a company in Blugaria. They have a very active group on Facebook and the default firmware supports MQTT as well as REST endpoint. The name of the devices is Shelly - the group homepage on Facebook is



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Another factor is that Sonoff devices now come with the ability to have a DIY mode - i.e. not dependent on the Sonoff App.

Shelly are good and (IIRC) can be flashed with ESPHome and Tasmota.

Correct - Shelly support being flashed