Hi all,

I’m looking for a reliable smart plug with current/energy monitoring that meets these requirements:

  • Ideally <1s time resolution (I need fast updates, not just averaged every few seconds.)
  • Wi‑Fi connectivity preferred, with MQTT client support out of the box (similar to how Shelly devices can publish to a local MQTT server when the load current changes. I'd rather not have to poll a device's HTTP endpoint a few times per second.)
  • Provisioning/config: Bluetooth for setup would be a big bonus (I think the Shelly Plug S Gen3 can do this, too.)
  • Reliability/manufacturer: Needs to be from a well‑supported brand or at least something that’s proven stable and not a "cheap no‑name" option.

I’ve been testing a few devices already. Most average power consumption over longer periods, while e.g. newer Shelly devices come frustratingly close to being exactly what I need.

Does anything on the market provide sub‑second resolution for current measurement? Most consumer plugs I’ve tried either average readings or only publish once every few seconds, which isn’t quite enough for my use case (measuring transient behavior and categorising operating modes of certain appliances).

Has anyone come across a plug that ticks these boxes? Or maybe a hidden configuration with Shelly devices that I’ve missed?

Thanks a lot for any help!

Edit: What I’m actually looking for is a fast response time to significant changes in power consumption (by more than a set amount or a percentage), so a high sample rate within the plug. A constant delay until the message is sent out wouldn’t be a problem at all.

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[–] 4 points 1 year ago (7 children)

Sonoff S31with Tasmota or ESPHome probably would do it. I'm not 100% sure the update interval sub second, but it's fast

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  • [–] [S] 1 point 1 year ago (6 children)

    Thanks, I'll look at that device.

    It's actually not so much the fast interval that I'm looking for, but fast response to changes in power consumption. In fact, I'd prefer not to be flooded by multiple messages per second but to only receive them on significant change (where "significant" would have to be configurable.)

    The Shelly AZ I have been thoroughly testing sends out MQTT messages when power consumption changes, but has a delay between 1.5 and 2.5s, sometimes up to 5s. If this were either faster or at least consistently delayed by the same time, I could use it.

    Reading up on Tasmota I've seen the PowerDelta configuration value which I think is what I am looking for...

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  • [–] 5 points 1 year ago (1 child)

    Since you have very specific requirements I would read up some more to make sure it fits the bill before you purchase one.

    You should also know that for either ESPHome or Tasmota you'll require a flasher (usb to TTL serial device) and some soldering skills (for the S31 there's also a 3d printable jig that exists)

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  • [–] 1 point 1 year ago (3 children)

    You'd be better off using helpers to do that, although I believe Esphome can do it using sensor filters.

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  • [–] [S] 1 point 1 year ago (2 children)

    You mean fire out data as fast as possible and take care of processing on the server? I'd be okay with that if necessary, but so far I haven't found one that seems to even measure the power consumption fast enough. They all average over some time frame between a few seconds and even minutes. This is of course fine for regular home appliances, but not fast enough for the problem I'm trying to solve.

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  • [–] 3 points 1 year ago (4 children)

    I've got several of the AthomTech smart plugs, they run Esphome, and you can fork their firmware and modify it as you see fit. I've got one pinging a fairly unstable server and will power cycle it if it doesn't get a response for 10min, all on device so it works without home assistant running.

    Here's it's config, defaults to 10sec, but you can change that easily

    github://athom-tech/athom-configs/athom-smart-plug-v2.yaml

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  • [–] 2 points 1 year ago (3 children)

    You can probably sample the data on the device at a much higher rate and send updates instantly if it's over a certain threshold

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  • [–] [S] 1 point 1 year ago (2 children)

    This together with runtime configurable thresholds would solve my problem completely.

    I ordered one of their ESPHome and one of their Tasmota models yesterday. When you talk about configuration, that actually means compiling a firmware binary and doing an OTA update, right? Or is it actually just a config file I give the device?

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  • [–] 2 points 1 year ago (1 child)

    It's a config that lives in Esphome on your home assistant server. Esphome has a Web based editor with some syntax help. When you click update it compiles it for you and uploads it ota.

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  • [–] 1 point 1 year ago (1 child)

    Beginner question here - does HA even take sub-second polling?

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  • [–] [S] 3 points 1 year ago

    To be honest, my question is not actually related to HA. I asked it here because it is by far the largest topic adjacent community on Lemmy and I was hoping to increase my chances of getting a good answer because all the home automation pros surely hang out here. You busted my con!

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  • [–] 0 points 1 year ago (1 child)

    curious what you are planning on using it for

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  • [–] [S] 2 points 1 year ago

    The goal is to measure precise on-time for certain kitchen appliances, and to be able to differentiate operating modes (e.g. standby vs. operating, potentially power setting when on.)

    It's not exactly that, but let's say you'd like to measure exactly how long a mixing device is mixing something, and you could guess the speed setting with some confidence.

    It actually isn't so much about receiving the data as fast as possible, but about precision in timing, which the plugs I've tested so far don't really offer. Best I have seen so far is ~2s delay with a standard deviation of up to another second on a Shelly AZ... Not good enough. The investigation continues.

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