Local watt meter for an electric panel?

I’m trying to find a dead simple device that can be a monitor for my mains at the panel, outside of Sense. It appears there are many Sense competitors with cloud based apps and the such, but that is not what I want. I am basically looking for a near analog (or digital) real-time monitor that will mimic Sense but solely installed just outside the panel. I want to see watts in real-time. Battery operated would be ideal.

Some of the $19 ones on Amazon aren’t for more than 5 amps or so, or they don’t do both main 120v feeds. Any recommendations?

This would not be outside of SENSE, but if you have an old cell phone or iPad you didn’t trade in, mount it on the wall by the panel. Connect to wifi and Go to the SENSE app — settings — My Home — SENSE Monitor, that will give you the system watts and volts. I believe @samwooly1 does something like that.

No I need it to work locally outside of the Sense ecosystem.

I don’t know of any metering devices that can monitor mains with the same real-time resolution as Sense. I have an Rainforest Eagle that reads the data from my smart meter in real time, but the data rate is slower (updates every 3-4 seconds). They also make an EMU meter that you could probably mount outside, but needs a supported smart meter.

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I think I found what I wanted. Something from this page:

I agree with @kevin1 and others. You’ll be hard pressed to find anything with the resolution and accuracy that matches what Sense does.

Looks to be cheaper to install a second Sense monitor for this purpose only.
Or you could repurpose the solar leads. The solar workaround would completely ruin your data for accurate tracking but the second monitor and account would not.

Sense requires Wifi, Internet and the rest of my infrastructure to work. I wanted something that would be more of a permanent install and could be used to track basic power usage if there was a power outage in conjunction with a generator.

Once I powered up all the circuits necessary to bring Sense back online I would be golden, but I would like something to register power usage before that. I do not own a powerful whole house genset so I need to be aware of my power usage at all times under all conditions.

That being said, I like the idea of using the Solar leads once it is up and running. I’ll have quite a few clamps in that breaker box!


  • Second Sense with main CTs on your 240V generator (mentioned elsewhere right?) … it can be offline (network) if you are offline and still function better than lesser options … you will be online (power) by default if there’s anything worth measuring.

  • Existing Sense solar CTs with 240V generator.

  • Depending upon the fickleness of your supply I wouldn’t rule out a UPS/PowerWall-like solution that may have the kind of integrated offline power monitoring you want. It could also allow you to have a 120V generator and 240V supply to your panel without a major headache.

  • If you have a good generator you might not need anything more than current detection to calculate load. I use Monnit systems for other reasons (risk management) but you can get kWhr readings and it will cache offline. More expensive than a second Sense but sensor options go way beyond current/voltage.

  • Look at auto-transfer switches and integrated management options. I would future-proof your thinking and expense by considering that you’ll have solar at some point (unless that’s ruled out for some reason). Get some solar quotes and quiz people about your integration issues?

ixu. Your Powerwall suggestion sent me down another rabbit hole. This looks…cool.

Could I use a Powerwall as an intermediary between my house electric panel and a mere 120v generator? In other words, if there is an outage, the Powerwall takes over everything and I can use a generator to back feed the Powerwall as it acts as an inverter for me? That sounds like the best of all worlds.
I live in Cleveland so solar power isn’t ideal, but I assume the Powerwall can stay charged with utility power?

I believe a single phase feed will suffice but I’m not sure. Others here may know.


That said if you can afford a Powerwall and the install then I would recommend a 240V generator anyway given the nominal price difference.

Or do a full-on cost analysis accounting for your “backup” expectations and usage. e.g. If you just need to power an efficient fridge; your Sense and a light or two during a grid fail you could keep things going for 48 hrs or more from a Powerwall2 (13.5 kWh) without bothering with a generator. If you want to run indefinitely then you’ll need to invoke fossil fuels (and the generator) or solar (into the panel via the Powerwall).

Tricks like keeping your fridge with high thermal mass (ice!) would also potentially come in to that analysis.

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All this is new to me. Wonderful choice and options. Much of it is not even need but want.

I could probably get away with a better 120/240V generator; call it a day and forget everything else, but living in suburbia makes something quiet like a Powerwall interesting. I really can’t run a regular 5000W+ generator in my neighborhood at night during an outage, regardless of how understanding the neighbors would be. But I could use a Powerwall to keep everything running at night, then bring out a smaller, quiet inverter generator to feed the Powerwall during the day. All this assumes, as you have stated, that I have an extended outage necessitating that.

I’m using a Reliance Electric device for my generator cut-over so I can balance both sides of the 240v as much as possible during a power outage. I’m using a manual system with a bypass lock 240v breaker in my panel. It’s rated for 30w continuous.

I also use a Powerback! alert by Reliance that runs off a battery to trigger a built-in alarm when the main power comes back on so I can switch back to regular power. I think it was around $20.

Admittedly this is beyond the scope of Sense (my apologies), but I’m not too concerned during a power outage how much I’m drawing other to not overload my gasoline powered generator and something to alert me when the power does come back on.

Aside from that, you can temporarily read using a VOM style handheld amperage meter which can go on a 120v supply line, one at a time. I don’t recommend this unless you’re an electrician or know what you are doing.

To put me back on topic and perhaps more to your point, my electric company digital power meter (includes an ethernet bridge and cooresponding app) and Sense I find is very much in sync which tells me the Sense unit is calibrated very well. Sense also gives me much more detaled information. Within 2 weeks it has found my fridge, 2 x dehumidifiers, my main AC unit, a heat pump, and the main microwave. I am missing some motors on the AC and dehumidifiers which I hope it will find later.


I used this one:

It’s not watertight, but it was temporary, so I just used a freezer bag and hung it outside the breaker panel. It auto scales correctly for a 120v or 240v circuit. There is a reset button so you can measure a day or week or month and then reset. If you are measuring your power from the street you should get one for each side of the 240 to neutral.

I am moving it to the Tesla’s 50 Amp circuit and mounting it in the sheetrock, should look good.

I have what you’re looking for - it’s called a Current Cost ENVI. I’m pretty sure they’re not made anymore (company went under or something) but they’re nice little units - simply Google it and you’ll find lots of reading.

I used it for years before upgrading to Sense. It basically consists of a set of CT Clamps (similar to what Sense uses) that go in your main panel and a battery operated transmitter that sends the data to a base station wirelessly. The transmitter runs for years on a set of D batteries.

The base station is a small LCD panel that shows an overall consumption number (updated about every second) and some other basic data. Power requirements are minimal (it just has a small wall-wart transformer) and that’s it - plug it in anywhere within 50-60 feet of the transmitter and you have a total energy used display.

I stopped using it when I upgraded to sense and it’s just sitting doing nothing now. If you or anyone else is interested in it, PM me…

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You have mail.

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One more cheap ($44) option:

Wow, for a modern app that’s dirt cheap. Much more so than Sense.