Cheap (ish) energy monitor

I have a Hob that I’d like to detect when when it’s on but detecting the increase in energy usage (as can’t directly wire it)

Anything out there that doesn’t cost the earth
I have seen the aeotec 3 clamp one but at over £100 it’s a bit dear for what I need it for


Is it 3 phase installation or its enough to monitor 1 phase. Look on Shelly devices, they have affordable solutions. There is also 3 phase meter coming in march.

One phase should be enough I believe - I just need to know when the hob goes on so that I can turn on the extractor fan - without inline wiring this is the only way I can think to do it…

Not sure what a Hob is, but many smart plugs have energy measurement.

It isn’t plugged - it is hard wired to the breaker (via a switched spur) as it’s 32A. Hence the need for an energy reader as I don’t want to mess with the high load directly

I believe that it uses 3 phase wiring! For this purpose there is no device fully supported by Homey yet AFAIK - see this post. I have older Aeon clamp meter that do report overall consumption to Homey, which would solve your problem. Or just wait for Shelly 3M once it will be available (mid March) and supported by Homey (unknown) :slight_smile:

I’m a little confused. What exactly do you mean by three phase wiring?
There is one wire with a live, neutral earth which passes to it. Presumably the measurement would just read current flow over the whole wire?
Certainly wouldnt need reading on the earth…

I used to have a non smart energy monitor and that just wrapped round a cable

Usually hobs are connected to 5 wires (Live1, Live2, Live3, Neutral and Ground) because of high power load. If its not the case and you have only 3 wires (Live, Neutral and Ground) then Shelly EM should work just fine.

Ah, I didn’t realize.
I’ll open up the spur later and take a gander.

Anyway, in all cases you will need to do some wiring with those meter devices :slight_smile:


I don’t mind doing some wiring, I just don’t want to stick something in the middle of the lead!! There is a plug socket right next to the hob in a cupboard so can wire into a plug for power for simplicity

Would a 50A clamp be okay on a 32a lead?

Sure why not? 50A is the max. current, so 32A is comfortable.

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So not home yet but the instruction manual of my job recommends H05V2V2-F wire if the original gets damaged. This seems to be 4 core, so assuming it’s 2live feeds, one neutral and one earth…)

What I don’t understand is why I’d need to read those separately… If I wrapped one around my incoming house line I’d get usage on the whole house, so if I wrap across both live wires (i.e. the whole wire) then surely I’d get the usage on the whole hob?

If your house is feed with 1 live wire, then this is true. However when your house is feed with 2 or 3 Live wires (we call that Phases) then the current between the Live wires are phase-shifted and that means they cannot be read wit one clamp.

Yeah, my house is fed with one wire. Presumably that works mean that both live wires would be in phase so I can just use a single clamp on the hob?

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Best way to check this is to open the hob connection box to see the wiring. If only 3 cables are connected to it (Live, Neutral, Ground) then Shelly EM + 1 Clamp will work just fine.