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submitted 1 month ago* (last edited 1 month ago) by tofubl@discuss.tchncs.de to c/homeassistant@lemmy.world

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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[-] Munkisquisher@lemmy.nz 1 points 1 month ago

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

[-] Munkisquisher@lemmy.nz 1 points 1 month ago

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

[-] wildbus8979@sh.itjust.works 1 points 1 month ago

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

[-] tofubl@discuss.tchncs.de 0 points 1 month ago

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...

[-] wildbus8979@sh.itjust.works 1 points 1 month ago

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)

[-] tofubl@discuss.tchncs.de 1 points 1 month ago

Sadly, manual reflash is sort of a non-starter for my specific situation, but I have found devices that ship with Tasmota and ESPHome preflashed. I ordered a few to test.

[-] Zwuzelmaus@feddit.org 1 points 1 month ago

with MQTT client support out of the box

I'm afraid you'd better give up that convenience of MQTT. It is a bit bulky when your highest prio is a speedy communication.

[-] RvTV95XBeo@sh.itjust.works 0 points 1 month ago

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

[-] tofubl@discuss.tchncs.de 1 points 1 month 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!

[-] RoganDawes@infosec.exchange 0 points 1 month ago

@tofubl try something with support for esphome?

[-] tofubl@discuss.tchncs.de 1 points 1 month ago* (last edited 1 month ago)

Thanks for the reply!

I have no experience with esphome. This list has many of the "usual suspects" (Nous A1T which I have yet to test, Shelly Plug S) but how will this solve my problem?

I see that there are a few like this one that come with esphome preinstalled (a requirement for me, I can't use smart plugs I individually have to reflash.) In the device's config file I see a variable sensor_update_interval: 10s. Is that what you mean?

[-] RoganDawes@infosec.exchange -1 points 1 month ago

@tofubl yeah, the idea would be to flash your own firmware configured precisely how you want it to work. update_interval: would be one of the knobs you could tweak. Just be aware that whatever you are feeding the readings to may end up storing a huge amount of data, if it is updating at more than 1Hz! The esphome sensor filters might also allow you to get rapid updates when it’s changing significantly, and reduce the rate when you don’t need it.

[-] tofubl@discuss.tchncs.de 1 points 1 month ago

Have ordered a few devices to test and will give it a go. Thanks!

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[-] jumping_redditor@sh.itjust.works 0 points 1 month ago

curious what you are planning on using it for

this post was submitted on 20 Aug 2025
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